HomeMy WebLinkAboutDeadIndian_403_PA-T1-2022-00174
ZONING PERMIT APPLICATION
Planning Division
51 Winburn Way, Ashland OR 97520
FILE #
________________________________
541-488-5305 Fax 541-488-6006
DESCRIPTION OF PROJECT __ _______________________________________________________
Pursuing LEED® Certification? YES NO
Y
DESCRIPTION OF PROPERTY
Street Address
514!EFBE!JOEJBO!NFNPSJBM!SPBE-!BTIMBOE-!PS
39 1E
411-!412-!418-!419-!41:-!421-!423-!3111
Assessor’s Map No. ____ __________________________________ Tax Lot(s) __________________________________
22-!22E-!23
F.2-!BJSQPSU!PWFSMBZ
Zoning ___ _________________________________ Comp Plan Designation ___ _______________________
APPLICANT
DIBODF!NFUDBMG!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!652.663.3559
Name Phone E-Mail
!!DIBODF/NFUDBMGABTIMBOE/PS/VT
Address __ ____________________________________________ City __________________ Zip
31!FBTU!NBJO!TUSFFU!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!BTIMBOE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!:8631
PROPERTY OWNER
Name Phone E-Mail
DJUZ!PG!BTIMBOE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!652.599.6698!!!!!!!!!!!!!!!!!!!!!!!!!!!BENJOJTUSBUJPOABTIMBOE/PS/VT
Address _ ____________________________________________________ City Zip
31!FBTU!NBJO!TUSFFU!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!BTIMBOE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!:8631
SURVEYOR, ENGINEER, ARCHITECT, LANDSCAPE ARCHITECT, OTHER
NIBHFEPSOADFOUVSZXFTU/DPN
Title _____________________Name ________________________________ Phone ___________________ E-Mail ________________________
QSPKFDU!FOHJOFFS!!!!!!!!!!!!!!!!!!NBSL!IBHFEPSO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!652.433.9:73
Address ______________________________________________________________ City _________________________ Zip _______________
2131!TX!FNLBZ!ES-!TVJUF!211!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!CFOE-!PS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!:8813
Title _____________________Name ________________________________ Phone ___________________ E-Mail ________________________
Address ______________________________________________________________ City _________________________ Zip _______________
I hereby certify that the statements and information contained in this application, including the enclosed drawings and the required findings of fact, are in all respects,
true and correct. I understand that all property pins must be shown on the drawings and visible upon the site inspection. In the event the pins are not shown or their
location found to be incorrect, the owner assumes full responsibility. I further understand that if this request is subsequently contested, the burden will be on me to
establish:
1)that I produced sufficient factual evidence at the hearing to support this request;
2)that the findings of fact furnished justifies the granting of the request;
3)that the findings of fact furnished by me are adequate; and further
4)that all structures or improvements are properly located on the ground.
Failure in this regard will result most likely in not only the request being set aside, but also possibly in my structures being built in reliance thereon being required to
be removed at my expense. If I have any doubts, I am advised to seek competent professional advice and assistance.
_____________________________________ __________________________________
Applicant’s Signature Date
As owner of the property involved in this request, I have read and understood the complete application and its consequences to me as a property
owner.
__________________________________
____________________________________________________
Property Owner’s Signature ( Date
required)
\[To be completed by City Staff\]
Date Received Zoning Permit Type Filing Fee $ __________
OVER
G:\\comm-dev\\planning\\Forms & Handouts\\Zoning Permit Application.doc
ZONING PERMIT SUBMITTAL REQUIREMENTS
APPLICATION FORM must be completed and signed by both applicant and property owner.
FINDINGS OF FACT – Respond to the appropriate zoning requirements in the form of factual statements or
findings of fact and supported by evidence. List the findings criteria and the evidence that supports it. Include
information necessary to address all issues detailed in the Pre-Application Comment document.
2 SETS OF SCALED PLANS no larger than 11”x17”. Include site plan, building elevations, parking and landscape
details. (Optional – 1 additional large set of plans, 2’x3’, to use in meetings)
FEE (Check, Charge or Cash)
LEED® CERTIFICATION (optional) – Applicant’s wishing to receive priority planning action processing shall
provide the following documentation with the application demonstrating the completion of the following steps:
Hiring and retaining a LEED® Accredited Professional as part of the project team throughout design and
construction of the project; and
The LEED® checklist indicating the credits that will be pursued.
NOTE:
Applications are accepted on a first come, first served basis.
Applications will not be accepted without a complete application form signed by the applicant(s) AND property
owner(s), all required materials and full payment.
All applications received are reviewed for completeness by staff within 30 days from application date in accordance
with ORS 227.178.
The first fifteen COMPLETE applications submitted are processed at the next available Planning Commission
meeting. (
Planning Commission meetings include the Hearings Board, which meets at 1:30 pm, or the full Planning Commission, which
).
meets at 7:00 pm on the second Tuesday of each month. Meetings are held at the City Council Chambers at 1175 East Main St
A notice of the project request will be sent to neighboring properties for their comments or concerns.
If applicable, the application will also be reviewed by the Tree and/or Historic Commissions.
G:\\comm-dev\\planning\\Forms & Handouts\\Zoning Permit Application.doc
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X:\\Projects\\Ashland, City of\\2021 - Taxiway Rehabilitation\\CAD\\Exhibits\\Planning Application and Utilities Exhibit\\S03_Physical and Environmental Constraints Review Permit.dwg
Updated 7/1/2019
Community Development Department
Planning Division
PRE-APPLICATION CONFERENCE
INFORMATION SHEET & SUBMITTAL REQUIREMENTS
PURPOSE
Pre-application conferences are required for all projects that require a Type I, Type II or Type III planning actions as
defined in Chapter 18.5.1 of the Ashland Municipal Code. Definitions for Type, I, II and III planning actions can be
found at www.ashland.or.us/code.asp. If you are unsure if your project falls into any of the categories listed, please
contact the Planning Division of the Community Development Department for assistance at (541) 488-5305.
The purpose of the pre-application conference is to allow the applicant and the City Staff to meet and discuss the
proposed project early in the development process. This early review and meeting helps to identify opportunities and
key issues prior to preparation and submission of the Planning application. Before a proposal goes before the Planning
Commission for approval, most of the issues can be worked out so that the project is ready for review with few
additional changes or conditions needed.
PROCESS
Requests for a pre-application conference must be submitted to the Planning Division a minimum of two weeks in
advance of the scheduled meeting. Pre-application conferences are scheduled for Wednesdays between 2:00 and
4:00 PM. These conferences are scheduled on a first come – first served basis. A time cannot be reserved without
payment and a complete submittal as described on the attachment.
The narrative and the plans are then electronically sent to each concerned department to review and return comments
to the Project Planner. Where applicable, other agencies such as the Oregon Department of Transportation and
Jackson County will be invited to comment.
At the conclusion of the pre-application conference, you will receive a list of comments on what you will need to submit
for your planning action. In some cases, the Project Planner may recommend waiving the pre-application meeting if
the pre-application comments are self-evident and there are no critical issues.
Once the pre-application comments are issued, you have six months to submit for your planning action. If more than
six months elapse from the time of the conference to your planning application, a second conference may be required
due to potential code changes.
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G:\\comm-dev\\planning\\Forms & Handouts/Pre-Application Information Sheet Submittal Requirements_FY2017-18
Planning Division
PRE-APPLICATION CONFERENCE APPLICATION
51 Winburn Way, Ashland, OR
97520
DESCRIPTION OF PROJECT
Project Description ____________________________________________________________________________________
UBYJXBZ!B!SFDPOTUSVDUJPO!BOE!SFIBCJMJUBUJPO!QSPKFDU
APPLICANT
!!DIBODF/NFUDBMGABTIMBOE/PS/VT
Name _______________________________________________ Phone ________________ E-Mail ___________________
DIBODF!NFUDBMG!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!652.663.3559
Address __________________________________________________ City _____________________ Zip ______________
31!FBTU!NBJO!TUSFFU!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!BTIMBOE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!:8631
PROPERTY OWNER
Name ________________________________________________________ Day Time Phone _________________________
DJUZ!PG!BTIMBOE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!652.599.6698
Address __________________________________________________ City _____________________ Zip ______________
31!FBTU!NBJO!TUSFFU!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!BTIMBOE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!:8631
DESCRIPTION OF PROPERTY
411-!412-!418-!419-!41:-!421-!423-!3111
Street Address _______________________________________ Assessor’s Map No. 39 1E __________ Tax Lot(s) ________
514!EFBE!JOEJBO!NFNPSJBM!SPBE-!BTIMBOE-!PS
SUBMITTAL REQUIREMENTS
To request a pre-application conference, submit this form with two sets of scalable plans, one large format 24”x36” and
one no larger than 11”x17”. Include the following information plus your submittal fee of $142.25 (check, Visa,
MasterCard or cash accepted):
1.Completed Application.
2.Narrative – Provide a written description of proposal and request. (If in Historic District, provide pictures of existing
structures, elevations of proposed structures and details of planned exterior design features and materials)
3.
Site Plan – The site plan should contain all applicable elements in the Site Plan Checklist (see reverse) plus any other
information pertinent to this proposal. The site plan will be checked to insure all applicable information is included at the
time the pre-application date is set.
4.Additional information -Provide in the narrative or with the site plan:
1)Number of acres in development
2)Total gross square footage of all structures
3)Number of stories on each structure
4)Indicate number of and square footage of:
a)Dwelling Units (include the units by the number of bedrooms in each unit – e.g. 10 1-bedroom, 25 2-bedroom, etc)
b)Office Spaces
c)Retail Units
d)Other Spaces
5)Percentage of lot coverage by:
aStructureseLandscapin
))g
b)Streets & Roadsf)Number of parking spaces
cParkin Areas/Drivewas Total square footae of landscaped areas.
)gyg)g
dRecreation AreashOther pertinent information of the proposed development
))
5.
LEED® Certification – Indicate whether project will be pursuing LEED® certification.
6.
Submittal Fee
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PRE-APPLICATION SITE PLAN CHECKLIST
YES NO N/A
1.Project Name
2.Owner Name
3.Site Address and Map & Taxlot Number
4.Vicinity Map - with street names and locations of all existing and proposed
streets within or on the boundary of the proposed development
5.Scale & North Arrow
6.Lot Layout with approximate dimensions for all lot lines
7.Zoning Designations in proposed development and surrounding properties
8.Location & Use of all proposed and existing building, fences and structures
9.Indicate which buildings are to remain and which are to be removed
10.Location of all landscaped areas. Indicate existing trees, size, species, and
approximate drip line (outer branch location). Identify trees to be removed.
11.Location and size of all public utilities in and adjacent to the proposed
development including water line and meter size, sewer lines, storm drain
lines, nearest fire hydrant.
12.Locations of drainage ways or public utility easements in and adjacent to
proposed development.
13.Location, size and use of all contemplated and existing public areas
14.Approximate topography (slope) of the site
15.Location of all parking areas and individual and handicap parking spaces,
ingress and egress on the site and on-site circulation
16.Use designation for the areas not covered by buildings (e.g. loading, storage,
vacant, open space, etc.)
17.Elevations of the building(s)
18.Construction materials – wood frame, masonry, etc. (If project is in a Historic
District provide pictures of existing structures and indicate proposed exterior
materials for siding, windows, trim and roofing)
OPU!BQQMJDBCMF-!OP!CVJMEJOHT
BGGFDUFE!PS!QSPQPTFE/
PRE-APPLICATION BUILDING INFORMATION
Please attempt to indicate the following (Note: if information is not known please leave blank)
1.Current Building Occupancy Type (select one):
a)Assembly = More than 50 occupants (e.g., Theaters, Restaurants, Nightclubs, Taverns and Bars,
Community Halls, Art Galleries, Places of Worship, Arenas, Bleacher’s, etc.)
b)Business = Less than 50 occupants (e.g., Professional Service Office, Barber and Beauty
Salons, Training and Skill Development not within a school or academic program, Bank, Print Shop,
etc.)
c)Educational (e.g., Schools K-12th Grade, Religious Educational Rooms and Auditoriums, Day
Care Facilities)
d)Factory (e.g., F- Occupancy’s include, among others, the use of a building or structure or
portion thereof, for assembling, disassembling, fabricating, finishing, manufacturing, packaging,
repair or processing operations that are not classified as Group H-Hazardous or Group S-Storage
Occupancy’s)
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e)High Hazard (e.g., H-Occupancy’s includes, among others, the use of a structure, or a portion
thereof, that involves the manufacturing, processing, generation or storage of materials that constitute
a physical or health hazard in quantities allowed in control areas complying with section 414 of the
Oregon Structural Specialty Code.)
f)Institutional (e.g., I-Occupancy’s includes, among others, the use of a building or structure or a
portion thereof for more than 16 persons, excluding staff, who reside on a 24 hr. basis in a supervised
environment and receive custodial care. Detoxification Facilities, Hospitals, Medical Care, Nursing
Homes, Congregate Living Facilities, Social Rehabilitation Facilities, Assisted Living Facilities,
Alcohol and Drug Centers, Correction Centers, Jails, Reformatories, Adult and Child Day Care
Facilities.)
g)Mercantile (e.g., Department Stores, Drug Stores, Markets, Motor Fuel-Dispensing Facilities,
Retail or Wholesale Stores, Sales Rooms.)
h)Residential (e.g., Single Family Residence, Hotels, Motels, Apartment Houses, Vacation Time
Shares, Congregate Living Facilities (more than 16 occupants), Assisted Living Facilities (with or
without a Memory Care Endorsement), Residential Treatment Facilities etc.)
2.Is a Change of Occupancy being requested? If yes, please indicate the proposed Occupancy Type:
(Sample Occupancy Types given above)
a)Assemblye)High Hazard
b)Businessf)Institutional
c)Educationalg)Mercantile
d)Factoryh)Residential
3.If Residential please indicate which type (select one):
a)R-1 Occupancy (e.g., Hotels (transient), Motels (transient), Boarding Houses (transient) with more
than 10 occupants)
b)R-2 Occupancy (e.g., Apartment Houses, Congregate Living Facilities (nontransient) with more
than 16 occupants, Dormitories, Hotels (nontransient), Motels (nontransient), Vacation Time Share
Properties, Boarding Houses (nontransient) with more than 16 occupants etc.)
c)R-3 Occupancy (e.g., Detached One and Two Family Dwellings and Townhouses, Adult Care
Facilities (six or fewer persons of any age less than 24 hrs.), Adult Foster Homes as defined in ORS
Chapter 443, or Family Child Care Homes located in a private residence as defined in the Oregon
Structural Specialty Code section 310.2. Buildings that do not contain more than two dwelling units,
Boarding Houses (nontransient), Child Care Facilities that provide accommodations for six or fewer
persons of any age for less than 24 hrs., Congregate Living Facilities (nontransient) with 16 or fewer
occupants, Lodging Houses etc.)
d)R-4 Occupancy (e.g., This occupancy shall include buildings, structures or portions thereof for
more than five but not more than 16 persons, excluding staff, who reside on a 24-hr. basis in a
supervised residential environment and receive custodial care, Congregate Living Facilities, Halfway
Houses, Social Rehabilitation Facilities, Alcohol and Drug Centers Assisted Living Facilities (with or
without a Memory Care Endorsement), Residential Care Facilities (with or without a Memory Care
Endorsement), Residential Treatment Facilities, Group Homes and Facilities etc.)
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4.Type of Building Construction: (e.g., Types I and II construction are those types of construction in
which the building elements listed in Table 601 of the Oregon Structural Specialty Code are of
noncombustible materials. Type III construction is that type of construction in which the exterior walls
are of noncombustible materials and the interior building elements are of any material permitted by
the Oregon Structural Specialty Code. Type IV Construction (Heavy Timber) is that type of
Construction in which the exterior walls are of noncombustible materials and the interior building
elements are of solid or laminated wood without concealed spaces. Type V Construction is that type
of construction in which the structural elements, exterior walls and interior walls are of any materials
permitted by the Oregon Structural Specialty Code.)
a)Type Id)Type IV
b)Type IIe)Type V
c)Type III
5.Is the building equipped or proposed to be equipped with a Fire Protection System (e.g., Fire
Sprinklers or Fire Alarms)
a)Yesb)No
Any questions regarding the pre-application conference or the formal land use application submittal can be
directed to the Ashland Planning Division at (541) 488-5305. The City of Ashland Land Use Code can be
found online at www.ashland.or.us/code.asp by clicking on Chapter 18 and selecting the desired section.
Pg.6 of 6
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X:\\Projects\\Ashland, City of\\2021 - Taxiway Rehabilitation\\CAD\\Exhibits\\Planning Application and Utilities Exhibit\\20211109_Pre-Applicaiton Conference Site Plan.dwg
CIPDATASHEET
AIRPORTLOCIDLOCALPRIORITY
BtimboeNvojdjqbmBjsqpsuTP43132
PLANNEDYEARTO
QbsbmmfmUbyjxbzSfibcjmjubujpo3133
PROJECTDESCRIPTIONCONSTRUCT
SKETCH:
Sfibcjmjubuf
Ofx!Ubyjxbz!Fehf
Ubyjxbz!B
Mjhiut!boe!Djsdvju
Ofx!Voefsesbjo
!Ofx!Nboebupsz
Tztufn
Ipme!Tjhot
JUSTIFICATION:
UifqbsbmmfmUbyjxbzjtdvssfoumztipxojouif3127PEBQbwfnfouNbjoufobodfsfqpsubt
tbujtgbdupszupqpps)sbohjohgspn82.91*/Xpsltfmfnfoutgpsuifqspkfdubsfhfofsbmnjmmboepwfsmbzpguif
ubyjxbz-ofxtvctvsgbdfesbjobhf-ofxubyjxbzfehfmjhiut-boebofxmjhiufenboebupszipmeqptjujpotjhot/
Fohjoffsjohjtboujdjqbufeuptubsujo3132xjuidpotusvdujpotubsujohjo3133/SfgfsfodfbuubdifeQNQebub
tiffutgspnPEB(t3127qsphsbn/
COSTESTIMATE:
$
ADMINISTRATION:1.Construction$4$
22-1982-97:-:99
ENGINEERING:$2$5$
315-9:2
INSPECTION:$3$TOTAL:$
299-3263-385-293
Federal(%)$State$Local(%)$
SPONSORVERIFICATION:Date(seeinstructionsheetorattachedcommentsformoreinformation)
ForeachandeveryDateofapprovedALPwithprojectshown
3116
projectasapplicableDateofenvironmentaldetermination(ROD,FONSI,CatEx)
403132
t
Dateoflandacquisitionorsignedpurchaseagreemen
O0B
Dateofpavementmaintenanceprogram
3127
DateofBenefitCostAnalysis(BCA)asrequired
O0B
SPONSOR'SSIGNATURE:DATE:
2104203128
PRINTEDNAME:TITLE:
TdpuuB/GmfvszEfqvuzEjsfdupspgQvcmjdXpslt
PHONENUMBER:EMAIL:
652.663.3523tdpuu/gmfvszAbtimboe/ps/vt
FAAUSEONLY
PREAPPNUMBERGRANTNUMBERNPIASCODEWORKCODEFAAPRIORITYFEDERAL$
INSTRUCTIONSFORCOMPLETING
CAPITALIMPROVEMENTPLANDATASHEET
ACapitalImprovementPlan(CIP)DataSheetmustbesubmittedforeachmajorworkitemthatisrequestingFederalassistanceover
SubmittalofthisinformationisnecessarytoeffectivelyadministertheAirportImprovementProgram.
thenext5years.
HEADERINFORMATIONIncludethenameoftheairport,theLOCID,thelocalpriorityoftherequestedwork,theprojectdescription
andthedesiredFederalfiscalyear(October1sttoSeptember30th)thatyoudesiretheproject.
SKETCHColorcodedsketchthatdepictsandidentifiesthescopeoftheproposedproject.Anaerialphotocanbeusedaslongasit
showstheproposedprojectinformation.
JUSTIFICATIONAnswersthequestionsofwhatitis,whyisitneededandwhatisthebenefit.Thisisaveryimportantpartofyour
CapitalImprovementPlan.Theinformationisrequiredtoaccuratelydeterminetheeligibilityofyourprojectanditspriorityfor
funding.ProjectswithoutadequatejustificationcannotbeaddedtotheCIP.Tohelpyoupreparesolidjustificationwehave
compiledthefollowinglistofsuggestions,whichyoucanusetosupportyourassessmentoftheneedforthisproject.Besuretolist
allreasonsandneedsforyourprojectandincludeadetaileddescriptionofexistingconditions.Useextrapagesifneeded.
Forpavementrehabilitationincludetheageofthepavement,distresses,PavementConditionIndex
(PCI)Rating(maybeabletoobtainthisinfofromODA),oranyotherfactorthatwouldaffectpavementlife.
ofpavement(apron,runway)anddimensions(linearfeetandwidthorsquarefootage).Also
Includetype
includewhatyouhavedonetomaintainthepavementoveritslifetimeandthedateofthelastmajor
rehabilitation(i.e.overlays,sealcoats,etc.)
Newtaxiways/taxilanesΑwhatwillthistaxiway/taxilaneserve?Doesitserveahangararea?Isita
widththatiswiderthanFAAstandards,
paralleltaxiway?Whatwidthareyouproposing?Ifyouproposea
indicatehowthatadditionalpavementwillbefunded.
youplantoadd.Indicatewhyyou
ForApronExpansionindicatethecurrentsizeoftheapronandwhat
needmoreapronspaceandhowtheapronareawillbeused(tiedownarea,etc).
ForfencingprojectsΑindicatetheheightofthefenceandlinealfootage.Also,explainwhythefenceis
needed(i.e.deerfencing,security,etc)
LandacquisitionexplainwhatthelandisneededforΑapproachprotection?Developmentsuchasa
newhangararea?Alsoincludeifitisfeeoreasement.Includeparcelnumbersandacreageofthoseparcels.
Pleasestateifresidencesorbusinesseswillbeacquired.
ForArrival/DepartureBuilding,providewhattypeoffacilityyoucurrentlyhaveandwhatyouplanto
build(squarefootage,typesofrooms)
COSTESTIMATETheestimateoftotalcostincludingtheFederal,StateandLocalshares.Forfirstyearprojects,attachadetailed
costestimateshowingunitcosts;aggregateinsquareyards(S.Y.),concretepavinginsquareyards(S.Y.)andasphalticpavingintons.
Separatethecostsforlandacquiredinfeeandlandacquiredineasement.Noteiftheprojectisdependentonothersourcesof
funding(i.e.otheragencygrants)
SPONSORVERIFICATIONTheverificationthattheprojectisproperlyplannedandisreadyto"go"withinthefirstyearoftheCIPfor
applicableprojects.Exceptforequipmentacquisition,proposeddevelopmentandlandacquisitionmustbeshownonanapproved
ALP,haveclearedenvironmentalprocessing,andthelandalreadyacquiredorhaveasignedpurchaseagreement.These
requirementsmustbecompletedbeforeaprojectcanbeconsideredforupcomingyearfunding.Forthe2ndand3rdyearsoftheCIP
towardssatisfyingtheserequirements.Dateeachitemverifyingthatallproject
program,thesponsorshouldbeworking
requirementsaresatisfied(checkmarksarenotacceptable).
The comments of this pre-applicationare preliminary in nature and subject to change based upon the
submittal of additional or different information. The Planning Commission or City Council are the
final decision making authority of the City, and are not bound by the comments made by the Staff as
part of this pre-application.
ASHLAND PLANNING DEPARTMENT SITE:
403 Dead Indian MemorialRd.
PRE-APPLICATION CONFERENCEAPPLICANT:
COA PW Dept.
COMMENT SHEET REQUEST:
Physical& Environmental
December 15, 2021ConstraintsReviewPermitfor Floodplain
Development
PLANNING DIVISION COMMENTS:
This pre-application conference is intended to highlight significant issues before the applicant prepares
and submits a formal application.
Summary:
For staff, the key consideration hereis
that the proposed work is within both the SFHA
andregulatory floodway.Because the proposed
project includes land alteration withinthe flood
plaina P&E Permit is required.
The City of Ashland airportlocated at 403 Dead
Indian memorial Rd has portions of its taxiway is
within both the regulatory floodway as well as the
Special Flood Hazard Area (SFHA)(100-year
floodplain). The SFHA is the area where the
National Flood Insurance Program's (NFIP's)
floodplain management regulations must be
enforced, and these require a strict adherence that
Figure 1: FEMA Firmette from MSC.FEMA.GOV
no development allowed in the floodway will have an
effectiveFIRMdate 4/5/2017
adverse impact on downstream properties in the event of
a storm event. The standard is a demonstration that there will be no additional rise of downstream flood
levels during a base flood event.Thefederal regulations governing the NFIP are found at 44 CFR 60.3.
In relevant part:
44CFR 60.3(d)(3): Prohibit encroachments in the floodway, including fill, new construction,
unless it
substantial improvements, and other development within the adopted regulatory floodway
has been demonstrated through hydrologic and hydraulic analyses performed in accordance
with standard engineering practice that the proposed encroachment would not result in any
increase in flood levels
within the community during occurrence of the base flood discharge.
(4) Notwithstanding any other provisions of § 60.3, a community may permit
encroachments within the adopted regulatory floodway that would result in an increase in base
flood elevations, provided that the community first applies for a conditional FIRM and floodway
revision, fulfills the requirements for such revisions as established under the provisions of § 65.12,
and receives the approval of the Federal Insurance Administrator.
Airport Taxi Restoration –403 Dead Indian Memorial Rd
December 15, 2021
Page 1
While this information was not included with the pre-application materials in earlier conversation with
PW staff the following exhibit was received which indicated that the full depth reconstruction would
increase the elevation of the taxi wayby up to a foot.The area in the flood plain / floodway is estimated
to be over half an acre then even with a half foot of elevation increase would result in an estimated 10-
12k cubic feet of fill.
Question
: Is there any way to do this project without increasing the elevationat all?
The application materials submitted for the preapplication are limited. A final application will be
required to include:
location of floodplainand floodwayand riparian buffer on project plans
An inventory of existing trees and tree protection plan(if any are affected)
Potentially address water resource protection zone.
Any work in this area will be requiredto be mitigated per 18.3.11.110
o
Grading and Erosion & Sediment control plan
Based on City GIS the average distance from the upland edge of the emigrant creek to the taxi way is
roughly 60-65 feet. The applicant will need to show the riparian buffer area and keep all work out of
this area.
See AMC 18.3.11.060.D for a Limited Activities and Uses permit approval criteria
Airport Taxi Restoration –403 Dead Indian Memorial Rd
December 15, 2021
Page 2
To the rightis an image from the
City GIS
0.258 ac in floodway
0.629 ac in 100-year zone.
geomorphological floodplain
considerations. Just because the
fill is being added outside of the
SFHA (500-year etc)those areas
cannotbe excluded from the no
rise analysis.
18.3.10.060Land Classifications
The following factors shall be used to determine the classifications of various lands and their
constraints to building and development on them.
A.Flood Plain Corridor Lands.
Lands with potential stream flow and flood hazard. The following
lands are classified as Flood Plain Corridor Lands.
1.All land contained within the 100-year Flood Plainas defined by the Federal Insurance
Administration and identified in the Flood Insurance Map (FIRM) adopted by the City Council as
provided for in AMC 15.10.
2.All land within the area defined as Flood Plain Corridor Land in maps adopted by the Council
as provided for in section18.3.10.070Official Maps.
3.All lands which have physical or historical evidence of flooding in the historical past.
4.All areas within 20 feet (horizontal distance) of any stream identified as a Riparian Preservation
Creek on the Physical and Environmental Constraints Floodplain Corridor Lands map adopted
pursuant to section 18.3.10.070Official Maps.
5.All areas within ten feet (horizontal distance) of any stream identified as a Land Drainage
Corridor on the Physical and Environmental Constraints Floodplain Corridor Lands maps adopted
pursuant to section 18.3.10.070Official Maps.
D.Severe Constraint Lands.
The following lands are classified as Severe Constraint Lands, which
have characteristics that severely limit normal development.
1.All areas that are within the floodway channels, as defined in AMC 15.10.
2.All lands with a slope greater than 35 percent.
Airport Taxi Restoration –403 Dead Indian Memorial Rd
December 15, 2021
Page 3
18.3.10.080Development Standards for Flood Plain Corridor Lands
For all land use actions that could result in development of the Flood Plain Corridor, the following is
.
required in addition to any requirements of AMC 15.10
A.Standards for Fill in Flood Plain Corridor Lands.
1.Fill shall be designed as required by the Oregon Structural Specialty Code (OSSC), and
Oregon Residential Specialty Code (ORSC), where applicable.
2.The toe of the fill shall be kept at least ten feet outside of floodway channels, as defined in
AMC 15.10, and the fill shall not exceed the angle of repose of the material used for fill.
3.The amount of fill in the Flood Plain Corridor shall be kept to a minimum. Fill and other material
imported from off the lot that could displace floodwater shall be limited to the following:
a.Poured concrete and other materials necessary to build permitted structures on the lot.
b.Aggregate base and paving materials, and fill associated with approved public and private
street and driveway construction.
c.Plants and other landscaping and agricultural material.
d.A total of 50 cubic yards of other imported fill material.
e.The above limits on fill shall be measured from April 1989, and shall not exceed the above
amounts. These amounts are the maximum cumulative fill that can be imported onto the site,
regardlessof the number of permits issued.
,
4.If additional fill is necessary beyond the permitted amounts in subsection 18.3.10.080.A.3
above, then fill materialsmust be obtained on the lot from cutting or excavation only to the extent
necessary to create an elevated site for permitted development. All additional fill material shall be
obtained from the portion of the lot in the Flood Plain Corridor.
5.Adequate drainage shall be provided for the stability of the fill.
6.Fill to raise elevations for a building site shall be located as close to the outside edge of the
Flood Plain Corridor as feasible.
J.Hazardous Chemicals.
Storage of petroleum products, pesticides, or other hazardous or toxic
chemicals is not permitted in Flood Plain Corridor Lands.
K.Fences.
Fences shall be located and constructed in accordance with subsection 18.3.11.050.B.3.
Fences shall not be constructed across any waterway or stream identified on the official maps adopted
pursuant to section 18.3.10.070, OfficialMaps. Fences shall not be constructed within any designated
floodway.
M.Local Streets and Utilities.
Local streets and utility connections to developments in and adjacent
to the Flood Plain Corridor shall be located outside of the Flood Plain Corridor, except for crossing the
Corridor, except as provided for in chapter 18.3.11, Water Resources Protection Zones (Overlays), or in
the Flood Plain Corridor as outlined below.
1.Public street construction may be allowed within the Bear Creek Flood Plain Corridor as part of
development following the adopted North Mountain Neighborhood Plan. This exception shall only
be permitted for that section of the Bear Creek Flood Plain Corridor between NorthMountain
Avenue and the Nevada Street right-of-way. The new street shall be constructed in the general
location as indicated on the neighborhood plan map, and in the area generally described as having
the shallowest potential for flooding within the corridor.
2.Proposed development that is not in accord with the North Mountain Neighborhood Plan shall
not be permitted to utilize this exception.
Airport Taxi Restoration –403 Dead Indian Memorial Rd
December 15, 2021
Page 4
18.3.10.110Development Standards for Severe Constraint Lands
A.
Severe Constraint Lands are extremely sensitive to development, grading, filling, or vegetation
removal and, whenever possible, alternative development should be considered.
B.
Development of floodways is not permitted except for bridges and road crossings. Such crossings
shall be designed to pass the 100-year flood without raising the upstream flood height more than six
inches.
Sections C and D deleted as they apply to hillside development only.
FEMA STANDARDS FOR NO RISE
Once you determine that a development will take place in the floodway, the next step is to demonstrate
that the development will not cause any increase in flood stage. FEMA defines “any” as meaning a zero
increase. It does not mean that you can allow a .1 foot or even a .01 foot increase –it means nothing
greater than 0.00 feet. If you do not limit the increase to zero, the small increases in flood heights from
individual developments will cumulatively have significant impacts on flood stages and flood damages.
Under NFIP minimum requirements it is assumed that there will be no cumulative increases
since the permissible increase for any single encroachment is zero.Guidance for Flood Risk
Analysis and Mapping https://www.fema.gov/sites/default/files/2020-
02/FloodwayAnalysis_and_Mapping_Nov_2019.pdf
Any project in a floodway must be reviewed to determine if the project will increase flood heights. An
engineering analysis must be conducted before a permit can be issued. The community's permit file
must have a record of the results of this analysis, which can be in the form of a No-rise Certification.
This No-rise Certification must be supported by technical data and signed by a registered professional
engineer. The supporting technical data should be basedon the standard step-backwater computer
model used to develop the 100-year floodway shown on the Flood Insurance Rate Map (FIRM) or Flood
Boundary and Floodway Map (FBFM). https://www.fema.gov/glossary/no-rise-certification-
floodways
Grading and Erosion Control
: A grading plan including the location of all areas of land disturbance,
including cuts, fills, driveways, building sites, and other construction areas is required. The total area of
disturbance, total percentage of project site proposed for disturbance, and maximum depths and heights
of cuts and fill must be included. An erosion control plan must be submitted with the application. The
erosion control measures are required to minimize the solids in run off from disturbed area as required
Storm Drainage:
Storm drainage plan must be submitted with the application. Storm drainage facilities
must direct surface water away from cut faces of fill slopes and be designed to avoid erosion on-site and
to adjacent downstream properties.
Planting and Irrigation Plan:
A planting/irrigation plan is required to demonstrate the manner in
which cut slope terraces and fill slopes will be revegetated. The vegetation used for these areas must be
nativeor species similar in resource value, which will survive, help reduce the visual impact of the
cut/fill slopes and assist in providing long-term slope stabilization.
Airport Taxi Restoration –403 Dead Indian Memorial Rd
December 15, 2021
Page 5
Tree Inventory & Evaluation:
The tree survey must locate all trees greater than six inches d.bh. and
identify the species of each tree and approximate extent of the tree canopy. Trees to be removed and in
areas that will be disturbed must be clearly identified. The name, signature and address of the person
preparing the tree survey must be indicated on the tree survey. The application must also address the
suitability of trees for conservation and demonstrate that the trees to be preserved have been
incorporated into the design. Trees to be removed, unless diseased, dead or a hazard must be replaced.
A tree-replanting plan must be submitted with the application.
Neighborhood Outreach:
Staff always recommends that applicants approach the affected neighbors,
particularly those who are likely to receive notice of an application, in order tomake them aware of the
proposal and to try to address any concerns that may arise as early in the process as possible. Notices are
typically sent to neighboring property owners within a 200-foot radius of the perimeter subject property.
Written Findings/Burden of Proof:
This pre-application conference is intended to highlight significant
issues of concern to staff and bring them to the applicant’s attention prior to their preparing a formal
application submittal. Applicants should be aware that written findings addressing the ordinance and
applicable criteria are required, and are heavily depended on when granting approval for a planning action. In
addition, the required plans are explained in writing below. The burden of proof is on the applicant(s) to
ensure that all applicable criteria are addressed in writing and that all required plans, written findings, and
other materials are submitted even if those items were not discussed in specific, itemized detail during this
initial pre-application conference.
18.3.10.050Approval Criteria
An application for a Physical Constraints Review Permit is subject to the Type I procedure in section
18.5.1.050and shall be approved if the proposal meets all of the following criteria.
A.
Through the application of the development standards of this chapter, the potential impacts
to the property and nearby areas have been considered, and adverse impacts have been
minimized.
B.
That the applicant has considered the potential hazards that the development may create
and implemented measures to mitigate the potential hazards caused by the development.
C.
That the applicant has taken all reasonable steps to reduce the adverse impact on the
environment. Irreversible actions shall be considered more seriously than reversible actions.
The Staff Advisor or Planning Commission shall consider the existing development of the
surrounding area, and the maximum development permitted by this ordinance.
Airport Taxi Restoration –403 Dead Indian Memorial Rd
December 15, 2021
Page 6
OTHER DEPARTMENTS’ COMMENTS:
BUILDING:
No comments at this time. Please contact the Building Division for any building codes-
related questions at 541-488-5305.
CONSERVATION:
For more information on available water conservation programs, including any
available appliance rebates or assistance with landscaping and irrigation system requirements, please
contact Water Conservation Specialist Julie Smitherman of Conservation Division at 541-552-2062 or
via e-mail to julie.smitherman@ashland.or.us. For information on any financial or technical assistance
available for the construction of Earth Advantage/Energy Star buildings, please contact Conservation
Analyst/Inspector Dan Cunningham at 541-552-2063 or via e-mail to dan.cunningham@ashland.or.us
ENGINEERING:
At the end of this document.Please contact Karl Johnson of the Engineering
Division for any Public Works/Engineering information at 541-552-2415 or via e-mail to
karl.johnson@ashland.or.us.
FIRE:
At the end of this document.Please contact Ralph Sartain from the Fire Department for any Fire
Department-related information at 541-552-2229 or via e-mail to ralph.sartain@ashland.or.us.
WATER AND SEWER SERVICE:
No comments at this time.. Please Contact Steve Walker at541-
552-2326or (walkers@ashland.or.us) with any questions regarding water utilities.
ELECTRIC SERVICE:
No comments at this time. Please contact Dave Tygerson in the Electric
Department for service requirements and connect fee information at (541) 552-2389 or via e-mail to
tygersod@ashland.or.us.
Airport Taxi Restoration –403 Dead Indian Memorial Rd
December 15, 2021
Page 7
APPICATION REQUIREMENTS
Submittal Information.
The application is required to include all of the following information.
a.The information requested on the application form at
http://www.ashland.or.us/Files/Zoning%20Permit%20Application.pdf.
b.Plans and exhibits required for the specific approvals sought (see below).
c.A written statement or letter explaining how the application satisfies each and all of the
relevant criteria and standards in sufficient detail (see below).
d.Information demonstratingcompliance with all prior decision(s) and conditions of
approval for the subject site, as applicable.
e.The required fee (see below).
The Ashland Land Use Ordinance, which is Chapter 18 of the Municipal Code, is available on-line in its
entirety at: http://www.ashland.or.us/SIB/files/AMC_Chpt_18_current.pdf
Written Statements
Please provide two copies of a written statements explaining how the application meets the approval
criteria from the sections of the Ashland Municipal Code listed below. These written statements provide
the Staff Advisor or Planning Commission with the basis for approval of the application:
Physical & Environmental Constraints:18.3.10.050
o
Development Standards for FloodplainLands: 18.3.10.080
o
Development Standards for Severe Constraint Lands: 18.3.10.110
o
Limited Activities and Uses Permit(Potentially): 18.3.11.060.D
o
Plans & Exhibits Required
Please provide two sets of exhibits (plans or drawings) addressing the submittal requirements from the
sections of the Ashland Municipal Code listed below. These exhibits are used to copy the Planning
Commission packets and for notices that are mailed to neighbors. Please provide two copies on paper no
larger than 11-inches by 17-inchesandreproducible copies that are drawn to a standard architect’s or
engineer’s scale.
Physical & Environmental Constraints:18.3.10.040
o
Sever Constraints: 18.3.10.110.D
o
Water Resource Protection Zone(Potentially): 18.3.11.100
o
Tree Preservation and Protection: 18.4.5.030,
18.3.10.090.D
o
PLANNING APPLICATION FEES:
P&E Constraints Permit$1,120.25
NOTE:
Applications are accepted on a first come-first served basis. All applications received are reviewed and must be found
to be complete before being processed or scheduled at a Planning Commission meeting. Applications will not be accepted
without a complete application form signed by the applicant(s) and property owner(s), all required materials and full payment.
Applications are reviewed for completeness in accordance with ORS 227.178.
For further information, please contact:
December 15, 2021
Aaron AndersonCFM,AssociatePlannerDate
City of Ashland, Department of Community Development
Phone: 541-552-2052or e-mail:aaron.anderson@ashland.or.us
Airport Taxi Restoration –403 Dead Indian Memorial Rd
December 15, 2021
Page 8
11.3How a No-Rise Certification is Developed
NFIP minimum criteria prohibit encroachments in the adopted regulatory floodway unless it has
been demonstrated through hydrologic and hydraulic analyses performed in accordance with
standard engineering practice that the encroachment will not cause any increase in flood levels
in the community during the base flood discharge. FEMA defines “any” as meaning a zero
increase. It does not mean that you can allow a .1 foot or even a .01 foot increase – it means
0.00 feet. Otherwise the cumulative effects of all of the developments in the floodway could
significantly increase flood stages. There should be no cumulative effects since the permissible
increase for any single development is zero.
This hydrologic and hydraulic analysis is commonly called a no-rise or zero-rise analysis and
results in a no-rise certification. A few states and communities perform the no-rise analysis
themselves, but most require the permit applicant to hire a qualified registered profession
engineer to perform the analysis and provide the no-rise certification.
Some communities require that the registered professional engineer submit the no-rise certificate
on a form such as the example in Figure 11-2. Other communities allow the engineer to submit
the certification in a letter. Either way is acceptable provided that all of the necessary information
is included. The no-rise certification must be accompanied by documentation to support the
finding that there will be no increase in flood stage including the results of the hydraulic study.
Generally, the process for conducting the hydraulic analyses is the same as that used for applying
for a FIRM or floodway revision (see Section 7).
The registered professional engineer obtains a copy of the model used to develop the
effective FIS from FEMA. For information on how to obtain copies of the effective
model, see FEMA’s Internet site at http://www.fema.gov/plan/prevent/fhm/st_order.shtm.
The engineer duplicates the results of the effective model (called the Duplicative Effective
Model).
The engineer makes any corrections to the effective model (called the Corrected Effective
Model) such as technical errors in the effective modeling or the inclusion of any floodplain
changes that occurred prior to the date of the effective model.
The engineer develops a model for existing conditions that reflects any modifications that
have occurred within the floodplain since the date of the effective model but prior to the
proposed development (called the Existing Conditions Model). Generally, one or more
additional cross sections will be necessary to model the impacts of the proposed
development and any modifications that are made to the channel or overbank areas to
compensate for any loss of conveyance.
The engineer modifies the Existing Conditions model to reflect the proposed development
at the new cross sections while retaining the currently adopted floodway widths (called the
Proposed Conditions Model).
Floodway Analysis and Mapping November 2019
Guidance Document 79 Page 28
The engineer compares the results of the Proposed Conditions Model to the Effective
Model or Corrected Effective Model to determine if there will be an increase in elevation
of the base flood or floodway elevations at any existing or new cross section.
If there will not be an increase in either of the elevations, the engineer can prepare and submit
the no-rise certification and the supporting technical documentation to the community (Figure 11-
2). If there will be an increase, the development will have to be redesigned to avoid the floodway,
compensation provided for the loss of conveyance, or there will need to be a floodway revision.
11.4 Evaluating “No-Rise” Analyses Submitted by Engineers
The community must prohibit development in the floodway unless it has been demonstrated
through hydrologic and hydraulic analyses performed in accordance with standard engineering
practice that the proposed encroachment would not result in any increase in flood levels within
the community during occurrence of the base flood discharge. It is the community’s responsibility
to make the determination that a development in the floodway will not cause any increase in flood
stage. You cannot depend solely on registered professional engineer’s no-rise certification and
must review and approve the submission.
A certification by a registered professional engineer does not constitute a warranty or guarantee
of performance, expressed or implied. Certification of data is a statement that the data is accurate
to the best of the certifier’s knowledge. Certification of an analysis is a statement that the analysis
has been performed correctly and in accordance with sound engineering practice. However, not
all engineers are equally skilled or experienced in performing technical analyses and there is room
for disagreements as to what constitutes standard engineering practice. Remember the
registered professional engineer works for the permit applicant and not the community. The no
rise certification is a valuable piece of information that you can use to help make your
determination, but you are not obligated to accept the no-rise certification if you have reason to
believe that it is not done correctly.
Communities that have city or county engineering departments or that contract for these services
are encouraged to develop their own in-house engineering capability to evaluate proposals for
floodway development and review no-rise certifications. If your community is part of a flood
control or water management district, they may be willing to provide this service for their local
governments. Some states that have their own state floodplain management regulations or that
maintain engineering staffs that conduct Flood Insurance Studies may also be willing to perform
this service for communities. If the development requires a floodway revision and you wish to
approve the development, forward the revision request to FEMA and it will do the review as part
of processing the request.
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Guidance Document 79 Page 29
Figure 11-2. Example of a No-Rise Certificate.
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Guidance Document 79 Page 30
Communities should look at the following when reviewing no-rise certifications.
The registered professional engineer should be experienced in conducting hydrologic and
hydraulic studies. You do not have to accept a certification if you do not feel that the
engineer is qualified to conduct the analysis.
The analyses must be conducted using the hydraulic model that was used to develop the
FIS if it is still available.
The analyses should be consistent with basic hydraulic principles. For example, there
needs to be smooth transitions in flood flows between cross sections. Abrupt changes in
floodway width for example should be avoided.
If the development is located between existing cross sections, additional cross sections
must have been surveyed at the site of the development to accurately model the impacts
of the development.
The analysis should not include unrealistic land use or hydraulic assumptions. For
example, if the analysis assumes that roughness coefficients used in the original FIS are
changed, the new roughness coefficients must reflect what is actually on the ground.
There should be no cumulative impacts if other property owners undertake similar
developments. It is important that there really is no increase in flood stage due to the
development.
If the no-rise analysis depends on adding additional flow areas to compensate for the
impacts of an encroachment, you must ensure that the flow area will be available in
perpetuity and that the floodwaters can get to and use that flow area. You will want to
require the applicant to apply for a floodway revision and adopt the revised floodway as
part of your ordinance.
Again, if you have doubts about the submission, contact your state or FEMA Regional Office for
assistance (http://www.fema.gov/business/nfip/nfip_regions.shtm).
If the analysis depends on a change in floodway boundaries to achieve “no-rise” and a floodway
revision will be required see Section 7, Obtaining a Revision to Floodway Boundaries. If you
approve the request and forward a request for a floodway revision to FEMA, FEMA will review
the hydraulic analysis when it reviews the request.
Generally, you must maintain documentation in your files of the hydraulic analysis, the no-rise
certification, and your determination indefinitely. FEMA or your state will ask to see the
documentation on your next Community Assistance Visit (CAV), and you will need the
documentation if your floodway is ever revised.
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12.0 Encroachment Requirements for Rivers and Streams without
Floodways
FEMA may also issue a FIRM that include rivers or streams where FEMA has conducted a
detailed study and established base flood elevations, but not designated a floodway. Generally,
these Studies are conducted in less densely populated areas where it is difficult to justify the
expense of conducting an engineering study that would include a floodway. These areas are
subject to the requirements at 44 CFR 60.3(c)(10) which requires a hydraulic analysis to ensure
that each development in the floodplain does not increase base flood levels by more than one
foot at any point in the community. The requirement at 44 CFR 60.3(c)(10) essentially applies
the same standard to these areas as would apply if a floodway were designated (the maximum
one foot rise in flood stage). The main difference is that the hydraulic analyses are conducted on
a case-by-case basis for each proposed development in the floodplain. Most communities pass
on the cost of performing this analysis to the permit applicant. The advantage of having a
floodway designated is that is that the community can review and permit development outside of
the floodway without requiring a hydraulic analysis and without passing the costs of that analysis
on to the permit applicant.
The requirement in 63.3(c)(10) only applies along rivers, streams, and other watercourses where
FEMA has provided base flood elevations. The requirement does not apply along lakes, bays
and estuaries, and the ocean coast. Generally, this type of data is provided as interim data and
the intent is to eventually re-map these areas to add floodways when funding becomes available
and the amount of development warrants the added cost to develop floodways.
Sometimes a decision is made not to designate a floodway on a stream because hydraulic
conditions on the river or stream do not lend themselves to modeling a floodway using standard
methodologies. Generally, FEMA, the state, and the community agree to an alternative
management scheme for the stream that achieves the same purpose as designating a floodway
or performing an encroachment analyses under 60.3(c)(10).
44 CFR 60.3(c)(10): Require until a regulatory floodway is
designated, that no new construction, substantial
improvements, or other development (including fill) shall be
permitted within zones A1-30 and AE on the community’s
FIRM, unless it is demonstrated that the cumulative effect
of the proposed development when combined with all other
existing and anticipated development, will not increase the
water surface elevation of the base flood more than one
foot at any point within the community.
12.1 Ways to Meet the 60.3(c)(10) Requirement
Section 60.3(c)(10) of NFIP regulations requires a hydraulic analysis to ensure that each
development in the floodplain does not increase base flood levels by more than one foot at any
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point in the community. One of the concerns that have been expressed about implementing the
requirement has been the cost of performing a hydraulic analyses for a small development such
as a single home. The costs of this analysis must be considered as part of the cost of developing
in the floodplain. The potential adverse impacts of development in the floodplain on upstream
and adjacent property owners can be significant and must be evaluated before the development
is allowed to occur. However, there are several ways a community can avoid or minimize these
costs:
Stay out of the floodplain entirely. Usually limited detail studies without floodways are
provided in rural areas or less densely populated areas where parcels are large and there
is a choice of building sites. In these cases, it is often in everyone’s best interest to design
the development so that the building sites are located outside of the floodplain. The
floodplain is preserved, and the permit applicant avoids the added costs of performing the
hydraulic analysis and of developing in the floodplain.
Limit development to backwater areas. It may also be possible to limit the development
to backwater areas that are not effective flow areas. Most floodplains have irregular
boundaries and include backwater areas that provide storage of floodwaters but play little
or no role in the conveyance of floodwaters. The velocity of floodwaters in these areas
may be zero or close to zero. There may also be floodplain areas that are separated from
the river or stream by a railroad or road embankment or a substantial levee that is at or
near the base flood elevation that parallels the river or stream. Areas behind these
obstructions also may not convey flood flows. These areas are not taken into account as
flow areas when the hydraulic model is developed of the floodplain. Development of these
areas will not increase flood stages. A qualified engineer can apply basic hydraulic
principles to identify these areas. The remainder of the floodplain is sometimes referred
to as a natural floodway.
Establish setbacks: Finally, it may be possible to develop a standard setback or an
algorithm for establishing setbacks along smaller streams in your community that would
serve the same purpose as 44 CFR 60.3(c)(10). You may already have adopted a setback
to preserve a natural stream buffer to protect water quality. Back-up your setback or
algorithm with engineering calculations to show that development will cause no more than
a one foot rise in flood stage. Be conservative. Test the setback or algorithm on a
reasonable number of cross-sections given the variety of stream conditions in your
community. If you choose this alternative, check with your state or FEMA Regional Office
first.
If you adopt either the second or third alternative and feel that permit applicants may challenge
your setbacks or other requirements, you can always allow the applicant the option of hiring an
engineer and submitting a (c)(10) analysis if they disagree. Most permit applicants are likely to
comply with your requirement as long as it is reasonable rather than to go to the expense of
paying for a hydraulic analysis.
12.2 Performing a 60.3(c)(10) Analysis
In those floodplains where FEMA has provided the community with base flood elevations, but no
floodway, the community must prohibit development unless it is demonstrated that the cumulative
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Guidance Document 79 Page 33
effect of the proposed development when combined with all other existing and anticipated
development, will not increase the water surface elevation of the base flood more than one foot
at any point within the community.
When evaluating the proposed development, you must assume that other like situated property
owners will want to develop their properties in the same manner as the permit applicant and that
eventually their properties will be developed. You must take their rights to develop into account
when evaluating a development to determine if it will cause no more than a one foot increase in
flood stage for the base flood. For example, if the permit applicant wants to build a house on fill
that extends 100 feet into the floodplain, you must assume that the property owners across the
stream encroach into the floodplain an equal amount. You must also make the same assumption
for upstream and downstream property owners on both sides of the river or stream. You are in
effect developing a floodway for that reach of stream. You need to extend your hydraulic analysis
far enough upstream and downstream to capture the cumulative impacts of all of this
development.
13.0 Obtaining a Revision to Floodway Boundaries
Generally, you must apply for and obtain a floodway revision from FEMA any time you want to
make a change in the FEMA-designated floodway boundaries even if the change is so small that
it would not be visible on your FIRM. Applicants for floodway revisions usually want to narrow the
width of the floodway or shift the location or alignment of the floodway to allow for a development.
Procedures for obtaining a floodway revision can be found in NFIP regulations at 44 CFR 65.7
Floodway Revisions.
Requests for floodway revisions must come from the community. It is your floodway that you
have legally adopted as part of your floodplain management ordinance. You probably held a
public hearing and met other due process requirements when you designated your floodway and
usually will have to meet the same requirements to adopt a floodway revision. You are not
obligated to revise your floodway merely because a permit applicant can demonstrate that it is
possible to narrow the floodway or change the floodway alignment. Remember that when you
revise a floodway boundary, you may impact on other property owners in your community. They
usually will have an interest in maintaining the current floodway alignment and must be notified
before you propose a Floodway Revision to FEMA.
13.1 Procedures for Applying for a Floodway Revision
Applications for floodway revisions are submitted using FEMA’s MT-2 Forms. The MT-2 Forms
and the accompanying instructions can be downloaded from FEMA’s web site
).
(http://www.fema.gov/plan/prevent/fhm/dl_mt-2.shtm
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Guidance Document 79 Page 34
44 CFR 65.7 Floodway Revisions. (a) General:
Floodway data is developed as part of FEMA Flood
Insurance Studies and is utilized by communities to select
and adopt floodways as part of the floodplain management
program required by Sec. 60.3 of this subchapter. When it
has been determined by the community that no practicable
alternatives exist to revising the boundaries of its previously
adopted floodway, the procedures below shall be followed.
You are under no obligation to request a floodway revision under 44 CFR 65.7 just because a
developer wants one. It is your floodway that you have adopted in accordance with your due
process requirements and you as a community must approve the proposal and submit it to FEMA.
Remember you are required to evaluate alternatives to the development that would meet the
requirements of your floodplain management ordinance and demonstrate that these alternatives
are not feasible before a LOMR will be issued by FEMA. In most situations there will be
alternatives that do not require encroachments into your floodway or floodplain that would not
require a floodway revision.
You will be required to submit evidence that all affected property owners and communities have
been notified of your intent to revise the floodway to assure that they are aware of potential
adverse impacts of the revision. Your community will also have to find that the revision and the
proposed project meet or are designed to meet all community floodplain management
requirements and that all necessary federal, state, and local permits have been or will be obtained.
The most commonly required federal permits are wetlands permits under Section 404 of the Clean
Water Act of 1972 and incidental take permits under Section 10 of the Endangered Species Act
of 1972. If the floodway revision is approved by FEMA, you will be required to adopt the revised
floodway as part of your floodplain management ordinance and use the revised floodway to
regulate future development.
The procedure for applying for a floodway revision requires a hydraulic analysis similar to that
required to demonstrate that a development would cause no-rise in the elevation of the base
flood. The main difference is that instead of evaluating the impacts of a development in the
floodway on the base flood elevation, the hydraulic analysis is instead demonstrating that the
proposed revised floodway including any modifications that have been made to the channel and
overbank areas within the revised floodway will carry the base flood without increasing the water
surface elevation of that flood more than one foot at any point in the community. This is the same
standard used to designate the floodway that is being revised.
13.2 Development Proposals that Exceed the One Foot Standard
There are limited situations where it may be necessary to allow development in the floodway or
the floodplain that would result in increases in the base flood elevation greater than that generally
allowed by NFIP minimum criteria. This could include:
A proposal for development in the floodway that would cause an increase in the base flood
elevation.
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A request for a revision to floodway boundaries that would result in a floodway that would
result in greater than the allowable one foot surcharge.
A proposal for development in a floodplain where no floodway has been designated that
would cause greater than a one foot increase in flood stage.
Generally, this type of development is discouraged. Designation of the floodway can already
cause up to a one foot increase in flood stage and even this one foot increase can substantially
increase upstream flood damages.
There are situations where it may be in the public interest to allow this development if no existing
buildings are impacted and future buildings are elevated or floodproofed to the new base flood
elevations. The procedure for obtaining a FIRM and floodway revision to allow this type of
development has been established at 44 CFR 65.12 of NFIP regulations. Section 65.12 was
developed to provide a mechanism to address several situations where it was thought to be in
the public interest to allow development in the floodplain that would otherwise violate the
provisions of the community’s floodplain management ordinance. These situations include:
Construction or increase in height of a dam or other water control structure particularly
when it would reduce overall flood damages. Without the procedure at Section 65.12 this
type of development would not be permitted under the community’s floodplain
management ordinance.
Construction or replacement of roads or bridges that cross the floodplain. In situations
where no existing development is impacted by the increase in flood stage there may be
considerable cost savings in building a bridge with a smaller waterway opening.
Other developments that have a net public benefit where there are no practicable
alternative actions that would comply with the community’s floodplain management
requirements.
The procedure can only be used in situations where no existing structures will be impacted by the
increase in the base flood elevation and only if all affected property owners are notified of the
proposed revision. If FEMA approves the revised floodway, the community must adopt the
revised floodway and higher base flood elevations and use them to regulate all future
development. Often agencies proposing to construct such facilities are willing to purchase and
relocate impacted buildings and purchase flowage easements to mitigate the impacts of the
increased base flood elevations.
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44 CFR 60.3(c)(13): Notwithstanding any other provisions
of Sec. 60.3, a community may approve certain
development in Zones A1-30, AE, and AH, on the
community’s FIRM which increase the water surface
elevation of the base flood by more than one foot, provided
that the community applies for a conditional FIRM revision,
fulfills the requirements for such a revision as established
under the provisions of Sec. 65.12, and receives the
approval of the Administrator.
44 CFR 60.3(d)(4): Notwithstanding any other provisions
of Sec. 60.3, a community may permit encroachments
within the adopted regulatory floodway that would increase
in base flood elevations, provided that the community
applies for a conditional FIRM and floodway revision, fulfills
the requirements for such a revision as established under
the provisions of Sec. 65.12, and receives the approval of
the Administrator.
Guidance for meeting the requirements of Section 65.12 can be found in the MT-2 Forms and
Instructions and in Appendix C. A community may allow this type of development only if applies
for and obtains a conditional FIRM and floodway revision and meets specific requirements in
Section 65.12. A FIRM revision will be required to reflect any increase in base flood elevations
due to the development. A floodway revision is required if there is a change in floodway
boundaries. Once the community obtains approval of the FIRM and floodway revision, it must
adopt the higher base flood elevations and revised floodway prior to permitting the development.
13.3 Meeting the Requirements of 44 CFR 65.12
Prior to permitting a proposed development in the floodway that would cause an increase in the
base flood elevation, a request for a revision to floodway boundaries that would result in greater
than the allowable one foot surcharge, or proposed development in a floodplain where no
floodway has been designated that would cause greater than a one foot increase in flood stage
the community must apply for and obtain approval from FEMA of a conditional FIRM and floodway
revision.
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Guidance Document 79 Page 37
44 CFR 65.12 Revision of flood insurance rate maps to
reflect base flood elevations caused by proposed
encroachments.
(a) When a community proposes to permit encroachments
on the floodplain when a regulatory floodway has not been
adopted or to permit encroachments upon an adopted
regulatory floodway which will cause base flood elevations
increases in excess of that permitted under paragraphs
(c)(10) or (d)(3) of s.60.3 of this subchapter, the community
shall apply to the Administrator for conditional approval of
such action prior to permitting the encroachments to occur
and shall submit the following as part of the application:
The requirements for obtaining conditional approval are found in 44 CFR 65.12. The community
must:
Evaluate alternatives to the development that would meet the requirements of 60.3(c)(10)
or (d)(3) and demonstrate that these alternatives are not feasible.
Provide individual notice to each property owner explaining the impact of the proposed
action on their property.
Obtain concurrence of the Chief Executive Officer of any other community impacted by
the proposed action.
Certify that no structures would be impacted by the increased base flood elevations.
Once the conditional map change has been approved by FEMA the community must adopt the
increased base flood elevations and revised floodway prior to permitting the proposed action. The
increased base flood elevations and revised floodway become part of the ordinance and apply to
all future development in the community.
You are under no obligation to request a floodway revision under 44 CFR 65.12 just because a
developer wants one. It is your floodway that you have adopted in accordance with your due
process requirements and you as a community must approve the proposal and submit it to FEMA.
Remember you will be required to evaluate alternatives to the development that would meet the
requirements of your floodplain management and demonstrate that these alternatives are not
feasible before a CLOMR will be issued by FEMA. In most situations there will be alternatives
that do not require encroachments into your floodway or floodplain that would exceed those
permitted in your floodplain management ordinance.
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Guidance Document 79 Page 38
14.0 Alterations and Relocations of Watercourses
Communities that participate in the NFIP are also required to assure that flood carrying capacity
of an altered or relocated watercourse in a floodplain is maintained. This requirement applies in
Zone A where FEMA has not provided base flood elevations as well as in Zones AE, A1-30, AO
and AH which have been studied in detail. In order to meet this requirement, communities must
assure that:
Any altered or relocated watercourse has the same or greater flood carrying capacity as
it did before the alteration occurred, and
Once the watercourse has been altered or relocated, the community has an affirmative
responsibility to assure that it is properly maintained.
The community is also responsible for notifying adjacent communities and the state coordinating
office prior to altering or relocating a watercourse and providing FEMA with a copy of this
notification.
44 CFR 60.3(b):
(6) Notify, in riverine situations, adjacent communities and
the State Coordinating Office prior to any alteration or
relocation of a watercourse, and submit copies of such
notifications to the Administrator;
(7) Assure that the flood carrying capacity within the altered
or relocated portion of any watercourse is maintained;
14.1 Definition of Watercourse
Watercourse is not defined in NFIP regulations, but generally means the channel of a river, stream
or drainage way and not the adjacent overbank areas. Placement of fill in the overbank areas
only and outside of the channel is not an alteration or relocation of a watercourse. The overbank
areas are addressed under the NFIP floodway requirements. Watercourses include not only
rivers or streams that are the source of flooding used to determine the base flood and the
floodplain boundaries, but also smaller streams, drainage ways and ditches within the floodplain
that could flood during smaller more frequent events.
14.2 Application
The requirement to maintain the carrying capacity of altered or relocated watercourses applies to
watercourses in all mapped floodplains. In a Zone A where no base flood elevations have been
provided by FEMA, the requirements are particularly important because there are no floodways
designated and no other requirements that would preserve the capacity of the floodplain to convey
floodwaters. Preserving the capacity of the watercourse to convey floodwaters will help prevent
flooding from becoming worse as the area develops. Historically, the failure to maintain the
carrying capacity of altered relocated channels has created numerous flood problems. For
example, it was common practice to force a natural stream into a pipe or culvert when developing
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Guidance Document 79 Page 39
an industrial area or a subdivision. Frequently these pipes or culverts did not have the capacity
to pass the 1% chance flood or even much more frequent floods. The result was chronic flooding,
repetitive flood losses, and eventually costly corrective measures.
Once FEMA provides a community with base flood elevations and a floodway is designated the
requirements continue to apply to the channel of the river or stream. The floodway designation
will prevent encroachments in the floodplain that cause more than a one foot increase in flood
stage while the (b)(6) and (b)(7) requirements will protect the capacity of the channel of river or
stream to convey floodwaters. The (b)(6) and (b)(7) requirements also will continue to apply to
watercourses such as smaller tributary streams and drainage ways within the floodplain even
though they are not the flooding source that produces the base flood elevation.
Communities are not required to maintain natural streams or channels and watercourses that
were altered or relocated before the community joined the NFIP. Natural streams and
watercourses that were altered or relocated before the community joined the NFIP are treated as
existing conditions that are taken into account when the floodplain is mapped by FEMA. FEMA
recognizes that maintaining natural streams can be costly to the community and often raises
environmental issues. Watercourses that were altered or relocated prior to the community’s
participation in the NFIP can also be costly to maintain and the community may not have the legal
authority to undertake or require their maintenance. However, if these watercourses do silt in or
become clogged with debris or other obstructions, FEMA will eventually have to re-map these
areas to reflect the increased flood hazard. The floodplain will likely become larger and the base
flood elevation will increase. It is usually in the best interests of communities to maintain these
pre-existing altered or relocated channels even though it is not required by FEMA to ensure that
flooding does not increase and to avoid the need for this remapping.
14.3 Maintaining the Carrying Capacity of the Watercourse
Communities must assure that the carrying capacity of the altered or relocate watercourse is
maintained. This means that the carrying capacity of the altered or relocated channel must be
the same or greater than the original watercourse. The community will have to undertake some
kind of analysis to assure that this occurs.
In undeveloped areas designated as Zone A where FEMA has not conducted a detailed
engineering study and not developed base flood elevations, this analysis can be as simple as the
community engineer reviewing the proposal and determining that:
The channel size and cross section are as big, and the channel is as straight as the original
watercourse and that there are smooth hydraulic transitions into and out of the altered or
relocated portion of the watercourse.
The channel sides and bottom are of the same or similar materials to the original
watercourse and that the roughness coefficient is roughly the same.
If there are substantial differences between the altered and relocated channel and the original
watercourse it may be necessary to require that the permit applicant submit a hydraulic analysis
by a registered professional engineer.
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Guidance for Flood Risk
Analysis and Mapping
Floodway Analysis and Mapping
November 2019
Requirements for the Federal Emergency Management Agency (FEMA) Risk Mapping,
Assessment, and Planning (Risk MAP) Program are specified separately by statute, regulation,
or FEMA policy (primarily the Standards for Flood Risk Analysis and Mapping). This document
provides guidance to support the requirements and recommends approaches for effective and
efficient implementation. Alternate approaches that comply with all requirements are acceptable.
For more information, please visit the FEMA Guidelines and Standards for Flood Risk Analysis
www.fema.gov/guidelines-and-standards-flood-risk-analysis-and-
and Mapping webpage (
mapping). Copies of the Standards for Flood Risk Analysis and Mapping policy, related guidance,
technical references, and other information about the guidelines and standards development
process are all available here. You can also search directly by document title at
www.fema.gov/library.
Floodway Analysis and Mapping November 2019
Guidance Document 79 Page i
Table of Revisions
The following summary of changes details revisions to this document subsequent to its most
recent version in Month Year.
Affected Section or
Date Description
Subsection
Initial version of new transformed guidance. The content
was derived from the Guidelines and Specifications for
Flood Hazard Mapping Partners, Procedure Memoranda,
November
First Publication
2016 and/or Operating Guidance documents. It has been
reorganized and is being published separately from the
standards.
Added Floodway along Levees section, incorporated
sections of the draft Floodway Guidance for Local
November
Sections 2 - 14
2019 Officials, and renumbered sections after added section.
Small format changes were also made.
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Guidance Document 79 Page ii
Table of Contents
1.0Introduction ..................................................................................................................... 1
2.0The Floodway and Why It Is Important ............................................................................ 1
2.1The Regulatory Floodway ............................................................................................ 2
2.2Requirements for Development in the Floodway .......................................................... 4
2.3Variances ..................................................................................................................... 5
2.4The Importance of Protecting the Floodway ................................................................. 6
2.5Legal Basis for Floodways ........................................................................................... 7
2.6More Restrictive State and Local Floodway Standards ................................................ 8
3.0How Floodways are Delineated in FEMA Flood Insurance Studies .................................10
4.0Hydrology .......................................................................................................................10
5.0Hydraulics ......................................................................................................................11
5.1Floodway Analysis ......................................................................................................13
5.2Steady State Floodway Analysis .................................................................................15
5.3Unsteady State Floodway Analysis .............................................................................17
5.4Levees and Floodways ...............................................................................................18
5.5Alternative Floodway Alignments ................................................................................19
5.6Floodways and Restudies ...........................................................................................19
5.7Community Adoption of a Floodway ............................................................................19
5.8Floodway Development by State and Federal Agencies .............................................19
6.0Floodway Coordination ...................................................................................................20
7.0Floodway Boundary Mapping .........................................................................................22
8.0Floodway Data Table ......................................................................................................22
9.0Deliverable Products ......................................................................................................23
10.0Floodway Analysis Review .............................................................................................23
11.0Evaluating Proposals for Floodway Development ...........................................................23
11.1The Types of Development that Must Be Evaluated ....................................................23
11.2Meeting the No-Rise Criteria .......................................................................................25
11.3How a No-Rise Certification is Developed ...................................................................28
11.4Evaluating “No-Rise” Analyses Submitted by Engineers .............................................29
12.0Encroachment Requirements for Rivers and Streams without Floodways ......................32
12.1Ways to Meet the 60.3(c)(10) Requirement ................................................................32
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Guidance Document 79 Page iii
12.2Performing a 60.3(c)(10) Analysis ...............................................................................33
13.0Obtaining a Revision to Floodway Boundaries................................................................34
13.1Procedures for Applying for a Floodway Revision .......................................................34
13.2Development Proposals that Exceed the One Foot Standard .....................................35
13.3Meeting the Requirements of 44 CFR 65.12 ...............................................................37
14.0Alterations and Relocations of Watercourses .................................................................39
14.1Definition of Watercourse ............................................................................................39
14.2Application ..................................................................................................................39
14.3Maintaining the Carrying Capacity of the Watercourse ................................................40
14.4Maintaining the Altered or Relocated Portion of the Watercourse ...............................41
14.5NFIP Community Rating System (CRS) Credits for Drainage System Maintenance ...42
List of Figures
Figure 2-1. An example of a Flood Insurance Rate Map showing the floodway, cross section
locations, and base flood elevations. .......................................................................................... 2
Figure 2-2. Cross section of a floodplain showing the floodway, floodway fringe, and surcharge.
........................................................................................................................................ 4
Figure 4-1. Flood frequency curve for a gaging station that relates the magnitude of the flood
discharges to the percent chance of exceedance. .....................................................................11
Figure 5-1. Surveyed cross section. .........................................................................................12
Figure 5-2. Flood Profile from a Flood Insurance Study. Note that in addition to the elevations
of various frequency floods, the Flood Profile shows the locations of the cross sections and of
bridges, culverts, and other water control structures. ................................................................13
Figure 5-3. Cross section of the floodplain showing the floodway, floodway fringe and
surcharge. The model assumes that the entire floodplain outside of the floodway is filled or
otherwise obstructed. ................................................................................................................14
Figure 11-1. Limiting development to the hydraulic shadow of an existing building or other
obstruction. ...............................................................................................................................26
Figure 11-2. Example of a No-Rise Certificate. ........................................................................30
Figure 14-1. Picture of a constructed channel in Arizona that is overgrown with vegetation (from
U.S. Geological Survey Scientific Investigations Report 2006-5108). ........................................41
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1.0 Introduction
This document provides guidance for floodway analysis, and all the components that accompany
it. A floodway is a tool to assist communities in balancing development within the floodplain
against the resulting increase in flood hazard. A regulatory floodway is defined as the channel of
a river or other watercourse and the adjacent land area that is reserved from encroachment in
order to discharge the base flood without cumulatively increasing the water-surface elevation by
more than a designated height. NFIP regulations and Standard SID 69 and 70 state: “Floodway
surcharge values must be between zero and 1.0 ft. If the state (or other jurisdiction) has
established more stringent regulations, these regulations take precedence over the NFIP
regulatory standard. Further reduction of maximum allowable surcharge limits can be used if
required or requested and approved by the communities impacted.”, and “If a stream forms the
boundary between two or more states and/or tribes, either the 1.0-foot maximum allowable rise
criterion or existing floodway agreements between the parties shall be used.” The portions of the
floodplain beyond the floodway are called the floodway fringe. The community is responsible for
maintaining the floodway to mitigate flood hazards; the community must not allow any activities
causing a rise in the Base Flood Elevation (BFE) in the regulatory floodway.
The baseline model for the allowable surcharge is the model used to determine the BFEs the first
time a floodway was adopted for the reach. Unless it is demonstrated that the model should be
revised for reasons other than encroachments into the floodplain, all subsequent revisions to the
floodway are limited to the maximum allowable surcharge above the elevations determined in the
base model. That way, as hydraulic models are updated to reflect encroachments into the
floodway fringe, the cumulative effect of those and future encroachments is limited to the
maximum allowable surcharge. If the model is revised for reasons other than encroachments into
the floodplain (such as increased discharges, shift in channel, modeling software advancements),
the revised model, excluding any revisions attributable to loss of conveyance areas resulting from
floodplain encroachment, is the base model for future floodway analyses.
Regulatory floodways are not normally delineated in coastal high-hazard areas (i.e., Zones V1-
30, VE, and V). The computation of regulatory floodways on riverine flooding sources in coastal
floodplains is based on the base flood discharge and elevations of the riverine flooding source
only. The regulatory floodway must be terminated at the boundary of the V1-30, VE, or V Zone,
or where the mean high tide exceeds the 1-percent-annual-chance riverine flood elevation,
whichever occurs further upstream.
2.0 The Floodway and Why It Is Important
Perhaps the most important function of a natural floodplain is to convey floodwaters from
upstream to downstream. The portion of the floodplain that conveys most of the floodwaters is
called the floodway. Obstructions placed in the floodplain block the flow of water and can cause
increased flood heights upstream from the obstruction and increased velocities of floodwaters
adjacent to and downstream from the obstruction. Preserving the capacity of floodplains to
convey floodwaters through the designation and preservation of a floodway has been an important
concept in floodplain management from the very beginning. Preserving the floodway prevents
development from occurring in the floodplain that will increase flood heights and damages to
upstream properties. The NFIP and nearly all state and local floodplain management programs
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have incorporated the concept of a floodway to convey floodwaters in their floodplain
management requirements.
2.1 The Regulatory Floodway
The NFIP defines “regulatory floodway” as the channel of a river or other watercourse and the
adjacent land areas that must
be reserved in order to
discharge the base flood
without cumulatively increasing
the water surface elevation
more than a designated height.
This designated height is one
foot for most NFIP
communities. FEMA will
develop a floodway for a
community as part of a Flood
Insurance Study. Floodways
are usually shown on the
community’s Flood Insurance
Rate Map (FIRM), but for many
older studies a separate Flood
Boundary and Floodway Map
(FBFM) was published.
An example of a FIRM with a
floodway is shown in Figure 2-
1.The cross hatched area in
Figure 2-1 within the floodplain
is the floodway. The locations of
Figure 2-1. An example of a Flood Insurance Rate Map
the cross sections are shown
showing the floodway, cross section locations, and base
and identified by a letter and the
flood elevations.
base flood elevations are
identified by numbers
representing the elevation. The dark shaded area outside the floodway is the 1-percent chance
floodplain or Special Flood Hazard Area and the light shaded areas (labeled Zone X) are the 0.2-
percent chance floodplain.
Community’s that participate in the NFIP that have been provided with floodway data by FEMA
are required to adopt a floodway that causes no more than one foot increase in the base flood
elevation at any point in the community. The increase in base flood elevation from the “no
floodway” to “with floodway” condition is called the surcharge. Most communities adopt the
floodway provided by FEMA although they can adopt an alternative floodway provided it meets
the one foot criteria. Once a community adopts a floodway, it must prohibit development in that
floodway unless it has been demonstrated through engineering analyses that there will be no
increase in flood stage. Some states and communities have adopted more restrictive floodway
standards than those adopted by FEMA.
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Guidance Document 79 Page 2
44 CFR 59.1 Definitions: “Regulatory Floodway” means the
channel of a river or other watercourse and the adjacent land
areas that must be reserved in order to discharge the base flood
without cumulatively increasing the water surface elevation more
than a designated height.
Designation of a floodway allows for part of the floodplain to be developed while at the same time
preserving the ability of the floodplain to convey flood discharges. The area within the floodplain
but outside the floodway is called the floodway fringe. The allowable one-foot rise in flood stage
or surcharge is a compromise intended to balance the rights of the property owner to develop
their property against the need to protect adjacent and upstream property owners from increased
flood heights and increased flood damages. If FEMA did not allow for some increase in flood
stage when designating a floodway, the floodway could comprise most of the floodplain and
development in the floodplain would be severely limited.
44 CFR 60.3(d): When the Administrator has provided a notice
of final base flood determinations within zones A1-30 and/or AE
on the community’s FIRM …and has provided data from which
the community shall designate its regulatory floodway, the
community shall:
(1) …
(2) Select and adopt a regulatory floodway based on the
principle that the area chosen for the regulatory floodway must
carry the waters of the base flood, without increasing the water
surface elevation of that flood more than one foot at any point;
CFR 60.3 was published in the NFIP regulations on October 26, 1976. However, the floodway
was being used in the NFIP for floodplain management prior to 1976 because there is reference
to floodways in the “The Flood Disaster Protection Act of 1973”. Figure 2-2 shows a cross section
of the floodplain and distinguishes between the floodway and floodplain width.
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Guidance Document 79 Page 3
Figure 2-2. Cross section of a floodplain showing the floodway, floodway fringe, and
surcharge.
Implications of allowing a one-foot rise: NFIP regulations
allow up to a one-foot rise in flood stage when designating the
floodway. If development occurs outside of the floodway in the
floodway fringe and there is an increase in flood stage, there will
be an increase in potential flood damages to adjoining and
upstream property. In densely populated areas with existing
development, even the allowable one-foot increase in depth of
flooding could significantly add to flood damages to upstream
property. Damages can also occur during the base flood to new
buildings in the floodway fringe that are elevated or floodproofed
to the base flood elevation. Additional areas may be flooded that
are not shown on the FIRM as floodplain and not subject to the
community’s floodplain management ordinance. In these
situations, the community may wish to adopt a more restrictive
floodway (surcharge less than one foot) to prevent this increase
in damages.
2.2 Requirements for Development in the Floodway
Once a community has adopted a floodway, it must prohibit development in the floodway unless
it has been demonstrated through hydrologic and hydraulic analyses performed using standard
engineering practice that the development will not result in any increase in flood levels during the
base flood. FEMA defines “any” as meaning a zero increase (greater than 0.00 feet). This
analysis is usually called a “no-rise” or “zero-rise” analysis and results in a “no-rise” or “zero-rise”
certification by a qualified register professional engineer. Remember that considerable
encroachment into the floodplain was already allowed when the floodway was designated by the
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Guidance Document 79 Page 4
community. Although some communities or states perform the hydrologic and hydraulic analyses
themselves, most require the permit applicant to obtain the services of a qualified registered
professional engineer to perform the analysis and provide the certification. The process for
meeting this requirement is described in Section 5. Unless the engineering analysis demonstrates
that there will not be an increase in the base flood elevation as a result of the development, the
permit must be denied.
44CFR 60.3(d)(3): Prohibit encroachments in the floodway,
including fill, new construction, substantial improvements, and
other development within the adopted regulatory floodway unless
it has been demonstrated through hydrologic and hydraulic
analyses performed in accordance with standard engineering
practice that the proposed encroachment would not result in any
increase in flood levels within the community during occurrence
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of the base flood discharge.
2.3 Variances
If a permit applicant requests a variance to allow for development in the floodway that would
cause an increase in flood stage, the variance request must be denied. NFIP variance criteria
at 44 CFR 60.6(a)(1) specifically prohibit the issuance of variances by communities for
development in a floodway that cause any increase flood levels during the base flood. Granting
this type of variance could violate other NFIP variance criteria since variances also cannot result
in increased flood heights, additional threats to public safety, extraordinary public expense,
create nuisances, or cause fraud or victimization of the public.
44 CFR 60.6(a) Variances: (1) Variances shall not be issued by
a community within any designated regulatory floodway if any
increase in flood levels during the base flood discharge would
result.
By designating a floodway, a community greatly simplifies the administration of its floodplain
management regulations. Floodplain permits outside of the floodway can be issued without
delays for costly hydraulic analyses. Property owners have a greater certainty as to what areas
of their properties they can develop and what areas they cannot and can plan accordingly.
Upstream property owners have a reasonable assurance that they will not be damaged by the
actions of downstream property owners.
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2.4The Importance of Protecting the Floodway
The primary benefit to designating a floodway and regulating development within that floodway is
to preserve a portion of the floodplain to convey flood waters from upstream or downstream.
Without these requirements, development over time would encroach into the floodway and
obstruct the flow of floodwaters thus increasing upstream flood elevations. Limiting development
in floodways provides important benefits to the community.
2.4.1 Preventing Increases in Damages to Upstream Buildings
Floodway requirements are different from most other NFIP requirements which are intended to
protect individual buildings from flood damages. The primary reason for designating a floodway
and limiting development in that floodway is to prevent encroachments in the floodplain from
blocking flood flows and increasing upstream flood stages. Without floodway requirements,
encroachments into the floodplain would eventually increase flood stages to the point where
upstream flood damages are significantly increased. Existing upstream buildings would be
flooded to greater depths and even buildings built in accordance with the community’s floodplain
management would eventually become susceptible to flood damage from the base flood. Before
floodway requirements were adopted by communities it was common for floodplain
encroachments such as bridges and their approaches or fill in the floodplain to cause increases
of several feet in flood stage potentially increasing flood damages.
2.4.2 Limiting Development in the Most Hazardous Areas of the Floodplain
Since floodways include the stream channel and the adjacent areas of the floodplain, they tend
to include the most hazardous areas of the floodplain with the greatest depths and velocities of
floodwaters and amount of debris. Most of these areas are not only hazardous, but they are
expensive to develop due the costs of meeting elevation requirements and designing buildings to
withstand flood forces. The floodway also will generally flood more frequently than other parts of
the floodplain. These areas pose a threat to public safety and are best avoided. If floodways
were developed, the likely result would be buildings isolated by deep and fast flood waters that
may jeopardize the safety of any building occupants as well as that of public safety employees
conducting search and rescue operations.
2.4.3 Protecting Natural Functions of Floodplains
Floodways also protect important natural functions of the floodplain that benefit the community
and its citizens. In addition to conveying floodwaters, floodways and the adjoining floodplains
(floodway fringe) provide flood storage and reduce flood velocities and peak flows. When left in
natural vegetation, they also protect water quality and reduce sedimentation in the river or stream.
Floodways often contain wetlands and generally provide critical riparian fish and wildlife habitat
including habitat for threatened or endangered species. Floodways can provide linear corridors
and greenways that allow for the migration of wildlife. Floodway requirements can be combined
with other regulatory programs such as those designed to protect water quality to achieve multiple
objectives. Floodways that provide open space in densely populated areas are an amenity that
can increase the value of adjoining property and enhance the tax base of the community.
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2.4.4 Appropriate uses of floodways
There are a number of economic uses that can be conducted in floodways that do not impact
flood stages. Where possible these uses should be encouraged.
Agriculture and forestry uses that do not involve buildings or use of fill.
Back yards, lawns, gardens, parking areas and play areas. Often subdivisions can be
designed so that there are building sites on each lot that are outside of the floodplain or at
least the floodway and that all floodway areas are preserved.
Private or public open space and recreation uses such as golf courses, campgrounds,
picnic grounds, boat launching ramps, wildlife and nature reserves, and similar uses.
When in public ownership, floodways can provide corridors for trail systems for hiking,
jogging, biking, or horse-back riding. Often these uses enhance the value of adjoining
properties.
Industrial and commercial uses such as parking lots and loading areas and airport landing
strips for light airplanes that do not involve buildings or use of fill.
If these uses require fill or construction of buildings, the developer will have to demonstrate that
the use will cause no rise in flood stages. Some of these uses such as campgrounds or parking
lots may not be suitable for areas subject to flash floods or areas that flood frequently.
2.5 Legal Basis for Floodways
Floodway regulations have withstood numerous challenges that they are an unconstitutional
taking of private property without just compensation. The challengers generally have argued that
floodway requirements are so restrictive that the owner is precluded from making an economic
use of their property. In nearly all cases the concept of the floodway has been upheld in the
Courts as an appropriate use of the community’s floodplain management authority. The important
point to remember is that floodway requirements are intended to prevent the actions of one
property owner from causing increased flood damages to adjacent or upstream property owners.
No property owner has a right to a use that would create a nuisance to adjacent properties.
The NFIP floodway requirements are not a prohibition on development within the floodway. They
establish a performance standard (no increase in flood stages) that is intended to avoid increasing
damages to adjacent and upstream property owners. If the development can be designed to meet
the performance standard, it can be permitted in the floodway provided that the development
meets other NFIP floodplain management requirements. Floodway requirements may increase
the cost of development or limit the size of the development and the developer may decide that
the development is no longer practicable and may choose to abandon the project or decide on an
alternative location for the development for economic reasons. However, this is an economic
decision made by the developer and does not result in a taking under the law.
There are also public policy interests in controlling development in what is generally the most
hazardous part of the floodplain. There can be increased costs to the community costs in
providing services to floodway development. More importantly there are significant threats to
public safety for any inhabitants in the floodway and the need for search and rescue and other
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emergency operations can place an additional burden on an already overwhelmed community.
For these reasons as well as to provide increased protection to adjoining and upstream property
owners, some states and communities adopt more restrictive (surcharge less than one foot)
floodway standards. The following sections provide guidance and requirements associated with
floodway determinations.
2.6 More Restrictive State and Local Floodway Standards
Several states have adopted floodplain management laws and regulations that are more
restrictive than NFIP minimum requirements. Communities in these states must comply with both
NFIP minimum criteria and the more restrictive state requirements. In addition, many communities
have adopted more restrictive floodways or placed added restrictions on floodway development.
2.6.1 More Restrictive Encroachment Standards
The most common state requirement is an encroachment standard that is more restrictive than
the NFIP one-foot rise criteria for designating floodways. Typically, these states limit the increase
in flood stages caused by designating the floodway to zero or to an amount such as .1 foot or .5
foot. Provided that the state has legally enforceable laws or regulations, FEMA recognizes these
state standards and maps floodways in communities in these states using the more restrictive
state standard. For rivers or streams that border two states, one of which has a more restrictive
floodway standard, the one-foot surcharge is used unless the states have mutually agreed on a
lesser criterion.
Individual communities can also request a more restrictive floodway be placed on their FIRM. In
the absence of a more restrictive state standard, FEMA’s policy has been to map a floodway for
the community using the one-foot surcharge and to put that floodway on the FIRM. FEMA will
then do one additional floodway analysis using the community’s more restrictive standard and
provide that floodway to the community. The Mapping Partner conducting the study must consult
with the appropriate FEMA Regional Office before developing a floodway for a community based
on a more restrictive community standard. Information on contacting the FEMA Regional Offices
.
can be found at http://www.fema.gov/business/nfip/nfip_regions.shtm
2.6.2 State Floodway Regulatory Programs
Several states directly regulate all or most development in floodways. These states have
engineering staffs that perform floodway analyses and review and approve permits for floodway
development. Both a state permit and a permit from the community may be required for a floodway
or floodplain development in these states. If your community is located in one of these states,
contact the responsible state agency for information on the state requirements.
2.6.3 Floodways that Preserve Floodplain Storage
The FEMA floodway is intended to limit the impacts of encroachments into the floodplain on the
hydraulics of the river or stream – the requirement prevents increases in flood elevations on
upstream or adjoining properties from exceeding the one-foot standard. The FEMA floodway
usually does not account for the effects of loss of storage on the hydrology of the river or stream
and on downstream flood heights due to increased peak discharges. Although loss of storage
usually does make much of a difference on rivers and streams with large watersheds, it could be
a significant factor in increasing flood stages on smaller streams, particularly those with wide
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floodplains that contain areas such as wetlands that store large amounts of floodwaters. Without
these upstream storage areas, floodwaters will concentrate more quickly increasing peak
discharges of floodwaters. The result will be increases in flood heights in downstream areas.
Under certain conditions the increase in downstream flood heights can be much greater than the
upstream hydraulic impacts of the encroachments. Some communities address storage by
incorporating loss of storage into their hydrologic and hydraulic models and develop a “storage”
floodway. Other communities designate wider floodways in areas of the floodplain that provide
storage such as wetlands.
A community can also address this issue by limiting the amount of fill that can be placed in the
floodplain, adopting wetlands ordinances, requiring large lot zoning, or requiring that
compensatory storage be provided as the floodplain is developed. Compensatory storage
ordinances require developers that fill in the floodplain to compensate for the loss of storage by
creating new storage elsewhere on the property that is comparable to the storage that was lost.
2.6.4 Alternative Floodway Criteria
Some communities use other criteria to designate their floodways. Typically, these criteria
include in the floodway those areas that are frequently flooded, have flood depths greater than a
specified depth, or areas where floodwaters exceed a certain velocity. Their grounds for using
these criteria for designating their floodways are that these areas are generally not suitable for
development or are too hazardous and a threat to the safety of the public. The severity of the
hazard is a function of the combination of the depth of flooding and the velocity of the floodwaters.
Even very shallow flood depths of 1-2 feet can be hazardous in areas of high flood velocities. For
example, floodwaters of 2 feet deep with velocities of 5 feet per second would be hazardous to
even an adult. A good rule of thumb is that the depth and velocity in feet per second should not
exceed 10. To meet NFIP minimum requirements these floodways must also not cause an
increase in the water surface elevation of the base flood of more than one foot at any point in the
community.
Another alternative is to designate a resource based floodway. Such a floodway must at a
minimum include the FEMA one foot floodway but can include areas that protect other important
natural floodplain functions. For example, the floodway could be expanded to include adjacent
wetlands, key riparian habitat, a setback to protect water quality, and similar areas. Communities
that adopt resource based floodways need to clearly explain the basis and purpose of their
floodway designation in their ordinance. Resource based floodways work best when combined
with restrictions on the uses allowed in floodways discussed in the next section.
2.6.5 Restrictions on Uses Allowed in Floodways
In addition to establishing more restrictive standards for designating floodways, some states and
communities limit the types of development that can occur in floodways. Generally, these states
and communities have determined that public safety issues created by locating buildings in the
floodway far outweigh any economic benefits of allowing the development. For example, several
states prohibit the placement of all buildings in the floodway or limit the floodway to open space
uses. One state prohibits new residential buildings in the floodway with exceptions for certain farm
residences. Along streams with relatively narrow floodways it may also be possible to prohibit
most alterations of the floodway with an allowance for any necessary road and bridge crossings.
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2.6.6 Regulating to a Base Flood Elevation that Includes the One Foot Surcharge
One of the major concerns regarding the NFIP floodway requirements is that they can result in up
to a one-foot increase in flood stage for the base flood within the community. The result is that
even buildings that are elevated or floodproofed to above the base flood elevation (BFE) can
eventually sustain flood damage during the base flood. Several states require that any increase
in flood stage that would result from the designation of a floodway be added to the BFE and the
buildings be protected to the increased elevation. In some instances, states or communities add
freeboard on top of the base flood elevation to account for uncertainties in the base flood
elevation, provide an increased level protection, or compensate for the increase in flood stages
that result from floodway encroachments.
2.6.7 Community Rating System (CRS)
Communities that adopt regulatory floodways that are more restrictive than NFIP minimum
requirements or apply more restrictive requirements within their floodways can receive credits
under the NFIP’s Community Rating System (CRS). The CRS provides discounts on flood
insurance premiums in those NFIP communities that implement floodplain management
programs that go beyond the minimum requirements of the NFIP. Contact your State or FEMA
Regional Office regarding the CRS or refer to the CRS page on the FEMA website at
for additional information.
http://www.fema.gov/business/nfip/crs.shtm
3.0 How Floodways are Delineated in FEMA Flood Insurance Studies
Flood Insurance Studies (FISs) are conducted on behalf of FEMA by a Mapping Partner that could
be a private consultant, a federal agency, a state agency, a special district such as a flood control
or watershed district, or a community. States, communities, or special districts that cooperate with
FEMA during the FIS process can become a Cooperating Technical Partner (CTP) to FEMA. FlSs
are conducted in accordance with FEMA’s Guidelines and Standards for Flood Risk Analysis and
Mapping using standard engineering models. Most detailed studies along rivers and streams have
been prepared using HEC-RAS or, its predecessor, HEC-2 developed by the U.S. Army Corps of
Engineer’s Hydrologic Engineering Center in Davis, California. Other FEMA approved hydrologic
and hydraulic models that can be used can be found on the Flood Hazard Mapping pages on
FEMA’s web site https://www.fema.gov/national-flood-insurance-program-flood-hazard-mapping.
There are two main components to a FIS that take place prior to the mapping of the floodplain
and delineating the floodway, and these involve defining the hydrology and hydraulics of the
stream being studied.
4.0 Hydrology
A detailed hydrologic analysis is conducted to determine the flood discharges that will occur
during the base flood and other representative floods including the 10-year (10-percent chance),
25-year (4-percent chance), 50-year (2-percent chance), and 500-year (0.2-percent chance)
floods at a location. Flood discharge is the quantity of floodwaters that will pass a particular
location for that frequency flood measured in cubic feet per second. Flood discharges can be
found in the Summary of Discharges table in the FIS report. Flood flow frequencies are
determined using data from stream gages if there is one on the stream being studied and
procedures described in Bulletin 17B, Guidelines For Determining Flood Flow Frequency
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(Interagency Advisory Committee on Water Data (1982). If stream gage data are not available,
flood discharges are determined using regression equations developed by the U.S. Geological
Survey or other agencies or approved rainfall-runoff computer models that combine rainfall or
snowmelt with characteristics of the watershed to obtain the flood discharges. For more
information, see General Hydrologic Considerations and Hydrology Rainfall-Runoff Analysis
Guidance.
An example of a flood frequency curve for a gaging station is shown in Figure 4-1. This curve
relates the magnitude of the flood discharges to the percent chanceof exceedance. The data
shown in Figure 4-1 include the annual peak data collected at the gaging station, the solid curve
representing the computed frequency curve and the dashed lines showing confidence limits that
depict the uncertainty in the computed curve. For the stream in Figure 4-1, the 1-percent annual
chance or 100-year discharge is 82,000 cubic feet per second (cfs).
Peak Discharge (cfs)
Figure 4-1. Flood frequency curve for a gaging station that relates the magnitude of the
flood discharges to the percent chance of exceedance.
5.0 Hydraulics
Once the flood discharges are determined, a hydraulic analysis is conducted to provide estimates
of the elevations of the various frequency floods and to designate the floodway. Often HEC-RAS
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Guidance Document 79 Page 11
or its predecessor HEC-2 are used to conduct this analysis although there are other FEMA
approved models that are appropriate. The hydraulic analysis creates a computer model of the
floodplain using the flood discharges, cross sections of the river or stream, and characteristics of
the channel and overbank areas such as their roughness coefficients, slope, and location and
size of any obstructions such as bridges and culverts.
Cross sections of the stream channel and the adjacent overbank areas are developed at regular
intervals along the channel using ground surveys, detailed topographic maps or digital elevation
data. A cross section is vertical slice of the channel and overbank areas taken perpendicular to
the direction of flow. See Figure 5-1 for an example of a surveyed cross section. Cross sections
must be located close enough together to reflect changes in the shape and slope of the channel
and overbank areas. For example, cross sections are taken to reflect changes in the width of the
floodplain, bridge and road crossings (several cross sections are required to model a bridge),
changes in floodplain land use, and other factors that may impact flood flows. The more changes
there are in the floodplain the more cross sections that are required for the hydraulic model. See
the FIRM in Figure 2-1 for examples of cross section locations.
Figure 5-1. Surveyed cross section.
Roughness coefficients (called Manning’s “n”) are determined for the channel and overbank areas
of each cross section. Roughness coefficients measure the friction in the channel and overbank
areas and are a significant factor in measuring the effectiveness of that portion of the channel or
overbank area in conveying flood waters. For example, floodwaters will flow more smoothly and
at higher velocities over a paved surface than if the area were heavily forested.
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Within the model, the flood discharges are routed through the model and the result of the hydraulic
analysis is a base flood elevation and a floodplain boundary at each cross section. The floodplain
boundary is then interpolated between the cross sections using available topographic information.
See Figure 5-2 for a flood profile from a FIS.
Figure 5-2. Flood Profile from a Flood Insurance Study. Note that in addition to the
elevations of various frequency floods, the Flood Profile shows the locations of the cross
sections and of bridges, culverts, and other water control structures.
5.1 Floodway Analysis
The next step in conducting the hydraulic analysis is to develop the floodway. Normally, the
Mapping Partner performing the hydraulic analysis will determine the floodway using equal
reduction of conveyance on opposite sides of the stream (also called equal degree of
encroachment). Equal reduction of conveyance means that that the conveyance on both sides
of the stream is reduced by an equal percentage. The computer model in effect squeezes the
floodplain by progressively eliminating the area of the cross section beginning at the edge of the
floodplain until the allowable one foot surcharge is reached at one of the cross sections. Usually
several computer runs are made to come as close as possible to the one foot surcharge at all of
the cross sections. The purpose of using equal reduction of conveyance is to ensure that like
situated properties are treated equally. This does not mean that that the floodway will be an equal
width on both sides of the stream. Since the stream channel meanders across the floodplain, the
amount of conveyance in the overbank areas will usually vary. Reducing the amount of
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conveyance by an equal percentage in both overbank areas usually is the fairest way to treat
property owners. See Figure 5-3 for a standard floodway schematic from a FIS report.
Figure 5-3. Cross section of the floodplain showing the floodway, floodway fringe and
surcharge. The model assumes that the entire floodplain outside of the floodway is
filled or otherwise obstructed.
It is also possible to determine a floodway by manually locating floodway boundaries at each
cross section and then running the computer model to determine if the floodway meets the one
foot surcharge criteria. This method is used to develop a floodway when equal reduction of
conveyance does not produce the desired results or to evaluate floodways proposed by
communities to determine if they meet allowable one foot surcharge.
The requirement that the increase in the base flood elevation due to the floodway not exceed one
foot at any point in the community generally results in many cross sections where the surcharge
is less than the allowable one foot. Usually the controlling factor is a single cross section where
the stage increase is 1.0 feet. In some situations, it is possible to fill up to the bank of the stream
without causing a one foot increase in flood stage. When this occurs the floodway boundary is
set at the bank station of the stream channel as defined in the model even though the allowable
one foot increase in flood has not been reached.
The floodway analysis will produce a floodway boundary at each cross section. Engineering
judgment is then used to interpolate the floodway boundary between the cross sections adhering
to hydraulic principles.
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The study assumes that the entire floodplain outside of the floodway has been filled or otherwise
obstructed and does not convey flood waters. For this reason, once a floodway has been
designated encroachment analyses are no longer required for development outside of the
floodway. Having a floodway considerably reduces the administrative costs of regulating
floodplain development since hydraulic studies do not have to be undertaken for individual
development proposals.
5.2 Steady State Floodway Analysis
Floodways as discussed in section 5.1 are determined by modeling the floodway fringe as a non-
conveyance area by encroaching the effective flow area. The technique of using artificially high
roughness coefficients must not be used for floodway analyses in one-dimensional steady flow
analysis. The Mapping Partner should use the most recent existing conditions model, or base
model discussed in section 1.0 as the base for the floodway analysis limiting surcharges to the
maximum allowable above the base conditions 1-percent-annual-chance profile. Typically, the
Mapping Partner should use an equal conveyance reduction method to establish the regulatory
floodway.
When flow is in the supercritical regime for man-made channels, or where velocity conditions are
such that normal encroachment analyses are not possible or are inappropriate, the encroachment
stations should be computed so that the allowable rise in water-surface elevation matches the
target water surface without exceeding the target energy grade line.
5.2.1 Boundary of Floodway Analyses
Most floodways are determined using a step-backwater model. If a floodway exists at the
downstream limit of study on the same stream as the study reach, the floodway must be
configured so that the floodway data at the downstream limit of study match the floodway data at
the upstream limit of the existing study. See Section 6 of the Contiguous Community Mapping
Guidance for more information about study tie-ins.
In case a discrepancy is identified between the floodway data table and floodway model, the
Mapping Partner must document the magnitude of and reason for the mismatch and suggest
remedies to the FEMA Project Officer. Once the data match, the floodway analysis is based on
a starting water-surface elevation associated with the maximum allowable surcharge, or the water
surface elevation resulting from application of a more restrictive requirement imposed by a state
or other jurisdiction. That way, future (allowable) revisions to the downstream floodway should
not create surcharges greater than the maximum allowable in the study reach.
If the study reach begins at the mouth of the stream, the Mapping Partner must start the
encroachment analysis at a width yielding the maximum allowable surcharge, or the water surface
elevation resulting from application of a more restrictive requirement imposed by a state or other
jurisdiction, for a normal depth calculation using the same friction slope as the unencroached
profile. If a floodway does not exist immediately downstream of the study reach, the Mapping
Partner should start the analysis sufficiently downstream of the downstream limit of study so that
differences in the starting conditions do not create surcharges greater than the maximum allowed
within the study reach. That way, future floodway designations downstream should not create
surcharges greater than the maximum allowable in the study reach.
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If a floodway exists at the upstream limit of study, the floodway must be configured so that the
floodway data at the upstream limit of the study match the floodway data at the downstream limit
of the existing study. If the relevancy of the existing study is in question issues associated with
tying into the existing analysis should be investigated and the Mapping Partner must seek
guidance from the FEMA Project Officer.
5.2.2 Storage Considerations
Storage considerations in hydrologic and hydraulic modeling of the unencroached condition
should be revised to reflect any encroachment into storage areas indicated by the floodway
configuration.
If designated storage areas behind structures are accounted for in the flood discharge
computations by routing the base flood hydrograph, no encroachment is to be allowed; and the
floodway encroachment stations should be equal to the base floodplain boundary of the storage
area designating the storage area as part of the floodway. In this case, the Mapping Partner
should use the same flood discharge for the unencroached and encroached profiles in the step-
backwater analysis to determine the surcharge values. However, if the storage capacity exists
but is not accounted for in the routing base flood hydrograph, it can be encroached; the Mapping
Partner should determine the flood discharges for the encroached profile downstream of the
structure by routing the 1-percent-annual-chance flood hydrograph through the reduced storage
area. In this case, the flood discharge for the encroached profile may be greater than the flood
discharge for the unencroached profile in the step-backwater analysis.
5.2.3 Tributary, Split and Diverted Flows
The regulatory floodway on a tributary stream is based on the base (1-percent-annual-chance)
flood discharge and elevation of that stream only and normally should not include consideration
of any backwater flooding from the main stream. Therefore, the floodway elevations in the lower
reach of a tributary subject to backwater flooding may be lower than those used to plot the Flood
Profiles. See section 7 of the FIS Report Technical Reference to see how this is portrayed in the
FIS.
The Mapping Partner should re-compute flood flow values along each flow path associated with
reaches with split and/or diverted flow situations, as described in Split Flow under Section 2.1.7,
in the Hydraulics One-Dimensional Analysis Guidance, under encroached (floodway) conditions.
If the primary flow path (originating reach) can safely carry the entire base flood flow without
increasing flood heights more than the maximum allowable surcharge, only the primary flow path
requires a floodway. If not, other flow paths require floodways.
The Mapping Partner should ensure that the overland flow segment on the mainstream remains
open by determining a separate regulatory floodway for the overflow path, or by a note on the
FIRM stating that the overflow area should remain unencroached until a detailed hydraulic
analysis is performed to establish a regulatory floodway. The Mapping Partner must inform the
FEMA Project Officer when overland flow paths lead into another jurisdiction where a regulatory
floodway has not been computed, thus necessitating that the overflow area remains
unencroached.
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The FEMA Project Officer may approve, as an alternative, that the Mapping Partner determine
the regulatory floodway on the main channel downstream of the overflow area by determining the
floodway profile with the total flow (including the flow lost as overflow). The Mapping Partner
should compare the water-surface elevations from the floodway profile to the water-surface
elevations of the 1-percent-annual-chance Flood Profile reflecting existing conditions (whose
discharges in the main channel have been reduced because of flow lost as overflow) to determine
surcharges. If the calculated surcharge is less than or equal to the allowable surcharge, the
regulatory floodway is depicted on the main channel only.
Otherwise, a separate regulatory floodway is defined for the overflow path. The Mapping Partner
should add a note to the Floodway Data Table or the FIRM to identify the segment of floodway
where the surcharge was computed using the reduced flow. The floodway should be revised
when the diverted flow does not occur anymore, and the flow is fully carried by the main stream.
5.2.4 Negative Surcharge Values
Surcharge values must be between zero and the maximum allowable value in the respective
community. Negative values in output data generally indicate excessive changes in velocity,
conveyance capacity, or floodway width at or downstream of the cross section with the negative
surcharge. Floodway configurations should be revised until all surcharge values are between
zero and the maximum allowable value. Reasons for deviating from this practice should be
coordinated with the FEMA Project Officer.
5.3 Unsteady State Floodway Analysis
The equal conveyance reduction approach is most applicable to a steady state, one-dimensional
model. In certain situations, equal conveyance reduction cannot be practically achieved in
defining the floodway configuration. The Mapping Partner may use one of the alternative methods
discussed below to determine the regulatory floodway configuration. Use of an alternative method
must be approved by the FEMA Project Officer and agreed to by the communities involved.
Steady state models do not consider lost storage in both effective and ineffective flow areas and
its impacts on flow rates and timing. However, for unsteady state models, encroachment into the
floodway fringe would impact flow rates; the degree depends on the amount of storage lost.
Encroachments result in storage decreases in both off-channel storage modeled with an
elevation-storage curve, and in non-conveyance areas modeled with artificially high roughness
coefficients. Input data for the elevation-storage curve or the values of roughness coefficients
should be revised to reflect the lost storage.
5.3.1 One-Dimensional Unsteady Floodway Analysis
The loss of storage in the floodway fringe of an unsteady model makes it likely that the peak
discharge in the floodway model will be larger than that in the unencroached analyses. The flow
rate increases are likely to cause elevation increases downstream even if the base flood is fully
within the channel. If surcharges increase when unsteady state modeling is used for a reach with
a previously determined steady-state floodway, the floodway width should be increased to meet
the maximum allowable surcharge limit, or other more restrictive requirements of a state or other
jurisdiction.
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The equal conveyance reduction method can be performed in unsteady state modeling through
an iterative process. In general, the Mapping Partner should follow procedures described in the
HEC-RAS User’s Manual (HEC, 2016) to perform unsteady flow floodway analyses. The
procedure uses a steady flow encroachment analysis to establish an approximate floodway and
import the encroachment stations to the unsteady flow model to verify that the surcharge is within
the maximum allowable limit. The Mapping Partner should incorporate peak flows from unsteady
flow runs to the steady flow model to estimate the encroachment stations. When rerunning the
steady flow model with encroachment stations, Mapping Partners should adjust downstream
boundary conditions to reflect increases of water-surface elevation due to encroachment.
An alternative method is to perform floodway analysis using an unsteady state model directly.
The Mapping Partner should use the base flood hydrograph as the inflow hydrograph and
determine encroachment stations by the equal conveyance reduction method.
Equal storage reduction may be applied in the floodway determination for streams with flooding
dominated by storage. In such systems, the difference between the equal conveyance reduction
method and equal storage reduction method is usually not significant. The equal storage
reduction method is simpler in both concept and application and could be considered as an
alternative approach for floodway determination.
5.3.2 Two-Dimensional Unsteady Floodway Analysis
When a hydrograph is routed downstream and constrained within the floodway with a given
surcharge, it moves water downstream at a different rate. If the floodway fringe is encroached,
the water that previously inundated the floodway fringe areas is pushed downstream due to
reduction of storage and may result in increased flow rate and water-surface elevation on the
downstream floodplain. The storage routing floodway procedure fills the floodplain grid elements
up to the maximum allowable surcharge before distributing flow to contiguous floodplain grid
elements. Because the maximum allowable surcharge is defined by the user, this procedure can
easily satisfy the floodway surcharge requirement. The method does not explicitly compute and
compare conveyance reductions; the Mapping Partner must get pre-approval from the FEMA
Project Officer to use this method and coordinate with the communities to get an approved
floodway configuration.
If the floodway was previously determined by a one-dimensional model, the Mapping Partner
should incorporate the encroachment stations into a two-dimensional model and run the two-
dimensional model to verify that the maximum allowable surcharge is not exceeded.
5.4 Levees and Floodways
For some communities, regulatory floodways may have already been delineated for levee-
impacted areas along a flooding source. The presence and hydraulic significance of a levee along
a flooding source with a regulatory floodway can affect which base model is encroached to define
the floodway, the placement of the floodway boundary on the map, and the stakeholders included
in the floodway coordination. FEMA has developed an approach for modeling and delineating the
regulatory floodway in levee-impacted area. This approach is outlined in the Levee Guidance.
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5.5Alternative Floodway Alignments
The standard methodologies for designating floodways work well for most rivers and streams.
However, there are unusual situations where it may not be possible to designate a typical one
foot flood rise floodway using the standard FEMA approved models or where one would make
little practical sense. Typical situations where this could occur are floodplains where flood waters
escape into an adjoining watershed, streams with beds that are perched above the surrounding
ground level, and extremely shallow floodplains where the flow areas are not adjacent the channel
of the river or stream. The FEMA Regional Offices generally address these situations on a case
by case basis in consultation with the State and the local governments affected with the overall
goal of maintaining sufficient flow areas to prevent increases in flood stage of one foot or greater
no matter where the water goes.
5.6 Floodways and Restudies
FEMA periodically conducts restudies of floodplains in communities where the current FIRM does
not adequately reflect the current flood hazard. Restudies are generally done when physical
conditions change in the watershed sufficiently to impact on flood stages, to reflect new flood
control structures, to incorporate better climate data, or take advantage of new mapping and study
technologies. When a restudy is done for a river or stream where a floodway has been
designated, the Mapping Partner conducting the study is directed to maintain the existing
floodway configuration wherever possible. If conditions have changed significantly, a new
floodway may have to be developed, particularly if a wider floodway is required to meet the one
foot rise criteria due to increased flood discharges. To the degree possible the new floodway will
reflect the effects of the encroachments that have occurred since the original floodway was
designated to ensure that flood stages do not increase more than the one-foot provided for in the
original FIS.
5.7 Community Adoption of a Floodway
When FEMA provides floodway data to the community, the community is required to adopt a
regulatory floodway that causes no more than a one foot increase at any point in the community.
There is no requirement that the community adopt the floodway on the FIRM as its regulatory
floodway. However, most NFIP communities do use the floodway on the FIRM rather than do the
hydraulic analyses necessary to develop their own floodway. The community, FEMA and the
Mapping Partner should work collectively to develop a floodway that meets the community’s
needs. If the community uses their own floodway in lieu of the FEMA floodway, it must be in all
instances wider than the FEMA floodway or the community must demonstrate that the floodway
meets the allowable one foot surcharge criteria. In either situation the community must consult
with the FEMA Region prior to adoption of the floodway.
5.8 Floodway Development by State and Federal Agencies
State and federal agencies also undertake development that could impact on floodways. For
example, State highway departments construct roads, highways, and bridges using federal or
states funds. Some of these state or federal agencies may be willing to apply for and obtain local
permits and most will at least coordinate with the community to make sure that their actions are
consistent with the requirements of the local floodplain management ordinance. Even if the
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agency maintains that it is exempt from local permits it must still comply with floodway
requirements comparable to those in your floodplain management ordinance.
Federal agencies are subject to Executive Ordinance 11988, Floodplain Management which
requires at a minimum that their actions be consistent with NFIP minimum requirements. All
federal agencies have adopted regulations that comply with Executive Order 11988 and should
be applying floodway requirements to actions that they undertake or fund. State highway
departments will be subject to Federal Highway Administration requirements each time they
construct a bridge or road using federal funds. States also will have floodplain management
regulations that will meet NFIP minimum requirements that will apply to their actions.
If a state or federal agency is undertaking development in a floodway in your community, you
should contact that agency to assure that they have undertaken the hydraulic analyses necessary
to assure that the development will not cause an increase in the base flood elevation within your
community. If you need assistance, please contact your NFIP State Coordinator or your FEMA
Regional Office (http://www.fema.gov/business/nfip/nfip_regions.shtm).
6.0 Floodway Coordination
The Mapping Partner ought to coordinate with the community when developing floodways. FEMA
typically starts with an equal conveyance methodology to determine the floodway. However,
because the floodway is the community’s tool to mitigate flood losses by restricting
encroachments into the floodplain, Mapping Partners must coordinate all regulatory floodway
determinations with community officials, as well as the NFIP State Coordinator and FEMA, as
early as possible in the study process.
Some communities may wish to propose a floodway alignment that is not based on equal degree
of encroachment (i.e. sometimes this is called a planning floodway). The approach for defining
the floodway should be incorporated into the communities’ ordinances to support the variance
from the equal conveyance floodway. Although generally the community should treat like situated
property owners equally, there can be competing community needs that can be met if the
community designates a floodway based on criteria other than equal degree of encroachment:
The floodway can be drawn to minimize the inclusion of existing development. For
example, there may be a developed or partially developed subdivision that would fall within
an equal degree of encroachment floodway. Since developed areas often do not
effectively convey floodwaters, floodways may need to be wider when these areas are
included.
The floodway can be drawn to accommodate proposed land uses. For example, the
community may have approved a subdivision in an area or extended sewer, water, streets
or other infrastructure to an area. There may be a need for a new bridge crossing and
there may be other anticipated needs.
The floodway can be drawn to be compatible with the communities land use plans or
zoning. For example, one side of the river or stream may be zoned for agriculture or other
low density use or be in parkland.
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The floodway can be drawn to include high hazard areas including areas subject to deep
flooding or high velocity floodwaters or areas that emergency vehicles could not access
during a flood.
The floodway can be drawn in a way that will prevent legal challenges by ensuring that all
existing parcels in the community have a building site.
Community designated floodways can be designed to meet the planning needs of the community
provided the community has a sound rationale for establishing the proposed floodway boundaries.
Evaluating a community designated floodway can require trial and error in order to meet the
allowable one foot surcharge which may increase study costs. For this reason, the Mapping
Partner needs to obtain prior approval from the FEMA Regional Office. Information on contacting
the FEMA Regional Offices can be found at
http://www.fema.gov/business/nfip/nfip_regions.shtm.
Where communities have adopted a regulatory floodway, the Mapping Partner must use the
configuration of the adopted floodway to the extent practical to compute floodway data along
restudied streams. If the surcharge values are greater than the maximum allowable above the
base condition, the Mapping Partner must inform the FEMA Project Officer and community. In
such cases, the Mapping Partner must coordinate a revised configuration with the community and
the FEMA Project Officer.
Where communities have not adopted a regulatory floodway or where the scope of work calls for
a revised configuration, the Mapping Partner must coordinate the floodway configuration with the
community and FEMA Project Officer. The Mapping Partner must discuss options for determining
the floodway with community officials and the FEMA Project Officer. Those discussions should
include:
The establishment of the base condition for this floodway determination and future
floodway revisions;
The effects of high velocities on fill, and structures and preferences the community may
have for restricting encroachments into high velocity areas or encroachments that may
result in high velocities elsewhere;
The restrictive nature of the regulatory floodway and means to distribute the restrictions
evenly, such as determining the limits through equal conveyance reduction on both sides
of the channel; and
The use of public land such as parkland to offset restrictions in other parts of the floodplain.
The agreed upon approach must be fully documented in the hydraulics report including the
reasoning leading to the encroachment methods and minutes of coordination meetings. Meeting
minutes must include the date, time, and location of the meeting and a list of attendees. If the
community cannot agree upon an approach, the Mapping Partner must consult the FEMA Project
Officer for direction.
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If more than one community is affected by the floodway, all affected communities must be included
in the discussions. In the case that one of the communities sharing the same reach has a more
stringent allowable maximum surcharge, the Mapping Partner must describe any differences in
maximum allowable surcharge values and facilitate an agreement among the communities as to
the maximum surcharge and the floodway configuration to be applied to the shared reaches. That
agreement must be fully documented including the date, time, and location of the meeting, and
signed by all parties in attendance. If such an agreement cannot be reached, the Mapping Partner
must seek guidance from the FEMA Project Officer.
If the state or community in which the mapping project is being performed has established more
stringent regulations for the maximum allowable rise in water-surface elevations, through legally
enforceable statutes, these regulations take precedence over the NFIP regulatory standard. In
the case of streams that form the boundary between two or more states, the 1.0-foot maximum
allowable rise criterion should be used unless the states have previously agreed on a lesser rise
criterion. The Mapping Partner must obtain written approval of the Regional Project Officer before
computing or mapping a second regulatory floodway based on a criterion established by the
community.
When the floodway has been established for either or both upstream or downstream communities,
the Mapping Partner must coordinate with all involved communities to create a smooth transition
of floodway surcharges and ensure the surcharges are within the maximum allowable limit.
7.0 Floodway Boundary Mapping
Floodways are delineated at the encroachment stations (limits of conveyance) at cross sections,
nodes or grid elements and interpolated between. For more information, see section 5 of the
Riverine Mapping and Floodplain Boundaries Guidance.
Where the floodway is mapped differently than the model results to meet state requirements, the
Mapping Partner should document the state requirements and the location(s) that discrepancies
occur.
8.0 Floodway Data Table
For each floodway determined under the scope of work, the Mapping Partner must create a
Floodway Data Table (FDT). The FDT developed as part of this analysis must contain an entry
for each cross section in the model to fully document the floodway analysis (this does not imply
that all cross sections will be shown in the FDT published in the FIS report). For more information
about the contents and appearance of the FDT see section 4 of the FIS Report Technical
Reference.
Existence of high ground in the middle of a cross section would reduce the floodway width,
computed as distance between two encroachment stations. In such a case, the width of floodway
should be the width as mapped and a note should be added to the FDT to explain the difference.
When creating a FDT based on a HEC-RAS unsteady flow floodway analysis, the Mapping
Partner should use floodway parameters (floodway width, section area, mean velocity of with-
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floodway and without-floodway water-surface elevation) associated with the maximum discharge
at each cross section from the unsteady floodway run.
Most two-dimensional models do not use cross sections. In those cases, the Mapping Partner
should create a set of cross sections and an associated FDT. The cross sections should be
placed at BFE contour lines and extend into the floodway fringe on both sides of the floodway.
Cross sections should be placed at changes in floodway width, spaced adequately to represent
stream characteristics, and with enough numbers to sufficiently represent the variation in floodway
data.
9.0 Deliverable Products
The floodway analysis and mapping must be submitted as part of the hydraulics and floodplain
submittal described in Section 6.6 and Section 6.9 of the Data Capture Technical Reference, and
Section 9 of the FIRM Database Technical Reference. The Mapping Partner must submit files
via the MIP; other media may be acceptable if coordinated with FEMA.
10.0 Floodway Analysis Review
The reviewing Mapping Partner will be responsible for performing hydraulic and floodway reviews
as described below. The reviewing Mapping Partner is responsible for determining whether the
proposed analyses are reasonable. Section 9 of the General Hydraulics Guidance provides
requirements and criteria that should be used to determine if the hydraulic and floodway analyses
are reasonable.
11.0 Evaluating Proposals for Floodway Development
Once a community has designated a floodway it must prohibit development within that floodway
unless it has been demonstrated through hydrologic and hydraulic analyses that the development
will not cause an increase in flood stages at any point in the community. Some communities
maintain their own in-house engineering expertise and perform these analyses themselves. Most
require that the permit applicant hire a qualified registered professional engineer to conduct the
analysis and submit it to the community for review and approval. This analysis is usually called
a “no-rise” or a “zero-rise” analysis and results in a “no-rise certification” if the analysis
demonstrates that there will not be any increase in the base flood elevation due to the
development. This section provides guidance on conducting and reviewing the “no-rise” analysis.
11.1 The Types of Development that Must Be Evaluated
The NFIP broadly defines development to include nearly all man-made changes to the floodplain.
Permits are required for all development to determine whether the development is subject to the
floodplain management requirements in the community’s ordinance. For development other than
buildings the primary purpose of the permit review is to determine whether the development is in
the floodway and, if it is, whether it will cause any increase in flood stage.
44 CFR 59.1 Definitions: Development means any man-
made change to improved or unimproved real Estate,
including but not limited to buildings or other structures,
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mining, dredging, filling, grading, paving, excavation or
drilling operations or storage of equipment and materials.
It is important to note that development includes additions to buildings that are less than
substantial improvements. These additions can obstruct flood flows and increase flood stages.
In addition, development includes the storage of equipment and materials. Activities such as the
stock-piling of sand or gravel or the storage of heavy machinery in the floodway can be as much
of an obstruction of flood flows during the base flood as the permanent placement of fill or
construction of a building. Unless you as a community can be absolutely sure that these
equipment or materials will be removed from the floodway prior to a flood, you must determine
that they will not cause any increase in flood stage before you can permit the use.
Communities can exercise some discretion and common sense in determining which
development requires permits or a hydraulic analysis. For example, you can exclude on-going
activities such as gardening and most forms of agriculture from your permitting requirements.
These activities generally do not change the existing grade of the ground in the floodway and will
not obstruct flood flows. Any related activities such as construction of levees that involve
placement of fill are covered in the definition of development and will require permits.
11.1.1 Exemptions for Minor Projects
There are other developments within the floodway that will require permits but can be allowed
once the community determines that they are not an obstruction to floodwaters. Small projects
that do not increase the natural grade, such as the paving of a driveway or parking area at the
existing grade can be permitted. There are other minor projects that probably will not increase
flood stages. For example, small isolated obstructions such as a mailbox, a pitcher’s mound, or
a single telephone pole can be permitted without requiring a no-rise certification. There is almost
no likelihood that these minor projects by themselves or in combination could cause a measurable
increase flood stage.
Common sense can also be exercised when evaluating proposals to place fences in the floodway.
Most types of fences such as barbed wire or chain link fences are likely to be knocked over by
floodwaters and debris long before flood heights approach the elevation of the base flood. Debris
will build up on these fences and the force of the water will push or bend the fence over. More
substantial fences such as solid wood privacy fences on small streams may obstruct flood flows
and will need to be evaluated. If in doubt, you have two choices. You can require the fence be
constructed in a manner that will assure that it will be knocked over and not obstruct flood flows
during the base flood (for example by requiring shallow embedment of the fence posts) or you
can require that the permit applicant obtain the services of a registered professional engineer to
design the fence or conduct a no-rise analysis.
If in doubt as to whether on obstruction will increase flood stages, the community should require
that the permit applicant conduct a hydraulic study to demonstrate that there will be no rise in
flood stage.
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11.2Meeting the No-Rise Criteria
Once you determine that a development will take place in the floodway, the next step is to
demonstrate that the development will not cause any increase in flood stage. FEMA defines
“any” as meaning a zero increase. It does not mean that you can allow a .1 foot or even a .01
foot increase – it means nothing greater than 0.00 feet. If you do not limit the increase to zero,
the small increases in flood heights from individual developments will cumulatively have
significant impacts on flood stages and flood damages. Under NFIP minimum requirements it is
assumed that there will be no cumulative increases since the permissible increase for any single
encroachment is zero.
There a number of ways a permit applicant can meet the no-rise criteria contained in the
community’s floodplain management regulations.
11.2.1 Redesign the Development to Avoid the Floodway
The best way to meet the no-rise criteria is to design or redesign the development so that no
obstructions are placed in the floodway. For example, when planning a subdivision, the plat can
be laid out so that the floodway areas are included in common open space or as backyards to
buildings that will be located outside of the floodway or even better outside of the floodplain.
11.2.2 Replace an Existing Building, Bridge, or Culvert
There are also situations where you may allow the replacement of an existing building or bridge
or culvert in the floodway without requiring a hydraulic study and a no-rise certification. For
example, the demolition of a building and the replacement of the building with a new building can
be permitted provided that the new building is contained within the footprint of the demolished
building. If you go outside of the footprint of the demolished building or change the location of the
building, the effect on flood flows may change and you will have to conduct a hydraulic analysis
and demonstrate that there will be no increase in flood stages. The replacement building will of
course have to comply with the other requirements of your ordinance. Your community may wish
to limit the replacement of buildings in the floodway. Although the new building should be
protected from flood damages during the base flood, it will be isolated by floodwaters and search
and rescue operations may be required.
It may also be possible to replace a bridge or culvert with an identical or larger bridge or culvert
and not cause an increase. However, new bridges and culverts are seldom identical to those that
they replace since design standards will change. Unless the new bridge or culvert is identical to
the one it replaces or the waterway opening is increased with no other change to the cross section,
you will have to conduct a hydraulic analysis and demonstrate that there will be no increase in
flood stage. Usually a hydraulic analysis will be required to design the bridge or culvert anyway
so the no-rise certification can be provided. Remember that replacement of a bridge or culvert
may provide an opportunity to solve an existing upstream or downstream flood problem.
11.2.3 Span the Floodway
For bridges on smaller streams it is sometimes possible to span the floodway with a waterway
opening sufficient in size to pass the base flood without causing an increase. This bridge would
meet the no-rise criteria. Generally, however, a hydraulic analysis would be conducted anyway
as part of the bridge design and a no-rise certification can be obtained as part of that analysis.
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11.2.4 Demonstrate That There Will Be No-Rise in Flood Stage through a Hydraulic Study
In some situations, it may be possible to demonstrate that a development will cause no increase
in flood stage by conducting a hydraulic analysis. Guidance for conducting hydraulic analysis and
making a no-rise certification can be found in Section 5.5 below. Generally, you can expect that
development in the floodway will cause an increase in flood stage. If the floodway has been
properly computed and displayed on the map, nearly all areas within floodway should effectively
convey floodwaters. When an increase occurs, it will be necessary to modify the development
proposal so that it no longer causes an increase in flood stage or to compensate for the increase.
Most communities require the permit applicant to hire an engineer to do the analysis and provide
a no-rise certification.
11.2.5 Limit the Development to the “Hydraulic Shadow” or “Conveyance Shadow” of
Another Obstruction
There are also situations where the development can be limited to the hydraulic shadow of a
building or other obstruction such as an isolated area of high ground that was in existence at the
time the floodway was designated. This should be only done for small projects such as building
additions or accessory buildings. The conveyance shadow includes the areas immediately
upstream and downstream of an existing building or other obstruction. Flood waters are already
flowing around the existing obstruction so that the new development will not affect the existing
flood flows. (See Figure 11-1.)
Figure 11-1. Limiting development to the hydraulic shadow of an existing building
or other obstruction.
Generally, the conveyance shadow is determined by drawing lines at a 1:1 ratio upstream and
downstream of the obstruction. Building additions or small accessory structures built entirely
within the conveyance shadow can be permitted without the engineering analysis needed for a
no-rise certification. The addition or accessory building must meet all other floodplain
management requirements in your ordinance.
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11.2.6 Compensate for Any Rise
If a development is in the floodway and will cause an increase in flood stage, it may possible to
compensate for the rise by physically modifying the floodway to replace the flood conveyance that
would be lost as a result of the development. Typical ways that this is done include:
Modifications to the channel or overbank areas of the cross section or channel
improvements to compensate for the loss of conveyance. Channel improvements are
frequently done as part of bridge design and construction. Modifications to the channel
and overbank areas and channel improvements must be permanent changes to the
floodway. The community must assume responsibility for maintaining the modification or
improvement or negotiate a maintenance agreement with the permit applicant. A floodway
revision as provided for in 44 CFR 64.7 will be required if floodway boundaries or base
flood elevations change.
Removal of an existing comparable obstruction such as a building or bridge. However,
you must usually conduct a hydraulic analysis to demonstrate that the net result will be no
increase in flood stage during the base flood.
Permanent changes in land use such as replacement of a floodplain forest with a ball field
or parking lot can also be used to compensate for loss of conveyance. However, there
must permanent changes in land use. Cutting down of trees to increase conveyance is
not a permanent change if the trees will grow back.
Expanding the floodway to replace the conveyance lost due to the obstruction. It may also
be possible to expand the floodway to compensate for the encroachment. This is usually
done to compensate for loss of conveyance from bridge piers or pilings. Unless the area
is in public ownership, expanding the floodway will generally require a floodway revision
to assure that the area remains available for conveyance of floodwaters.
Each of these alternatives will require a hydraulic analysis to demonstrate the result of the
compensation is that there will be no increase in flood stage during the base flood.
11.2.7 Floodway Revision
It may be possible to revise the floodway boundaries so that the development is no longer in the
floodway while still meeting the allowable one foot surcharge. You can sometimes narrow the
floodway at the location of the development or shift the floodway alignment so that that the
development is no longer in the floodway while still meeting the one foot surcharge limitation.
Usually this will require the surveying of additional cross sections to more accurately model the
floodway at the location of the development. If you want to do this, you must obtain a floodway
revision as provided for in 44 CFR 64.7 of NFIP regulations. Floodway revisions must be applied
for by the community since it is the community’s adopted floodway that is being changed.
Procedures for obtaining floodway revisions are described in Section 7. The floodway revision
must be obtained prior to proceeding with the development.
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11.3How a No-Rise Certification is Developed
NFIP minimum criteria prohibit encroachments in the adopted regulatory floodway unless it has
been demonstrated through hydrologic and hydraulic analyses performed in accordance with
standard engineering practice that the encroachment will not cause any increase in flood levels
in the community during the base flood discharge. FEMA defines “any” as meaning a zero
increase. It does not mean that you can allow a .1 foot or even a .01 foot increase – it means
0.00 feet. Otherwise the cumulative effects of all of the developments in the floodway could
significantly increase flood stages. There should be no cumulative effects since the permissible
increase for any single development is zero.
This hydrologic and hydraulic analysis is commonly called a no-rise or zero-rise analysis and
results in a no-rise certification. A few states and communities perform the no-rise analysis
themselves, but most require the permit applicant to hire a qualified registered profession
engineer to perform the analysis and provide the no-rise certification.
Some communities require that the registered professional engineer submit the no-rise certificate
on a form such as the example in Figure 11-2. Other communities allow the engineer to submit
the certification in a letter. Either way is acceptable provided that all of the necessary information
is included. The no-rise certification must be accompanied by documentation to support the
finding that there will be no increase in flood stage including the results of the hydraulic study.
Generally, the process for conducting the hydraulic analyses is the same as that used for applying
for a FIRM or floodway revision (see Section 7).
The registered professional engineer obtains a copy of the model used to develop the
effective FIS from FEMA. For information on how to obtain copies of the effective
model, see FEMA’s Internet site at http://www.fema.gov/plan/prevent/fhm/st_order.shtm.
The engineer duplicates the results of the effective model (called the Duplicative Effective
Model).
The engineer makes any corrections to the effective model (called the Corrected Effective
Model) such as technical errors in the effective modeling or the inclusion of any floodplain
changes that occurred prior to the date of the effective model.
The engineer develops a model for existing conditions that reflects any modifications that
have occurred within the floodplain since the date of the effective model but prior to the
proposed development (called the Existing Conditions Model). Generally, one or more
additional cross sections will be necessary to model the impacts of the proposed
development and any modifications that are made to the channel or overbank areas to
compensate for any loss of conveyance.
The engineer modifies the Existing Conditions model to reflect the proposed development
at the new cross sections while retaining the currently adopted floodway widths (called the
Proposed Conditions Model).
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The engineer compares the results of the Proposed Conditions Model to the Effective
Model or Corrected Effective Model to determine if there will be an increase in elevation
of the base flood or floodway elevations at any existing or new cross section.
If there will not be an increase in either of the elevations, the engineer can prepare and submit
the no-rise certification and the supporting technical documentation to the community (Figure 11-
2). If there will be an increase, the development will have to be redesigned to avoid the floodway,
compensation provided for the loss of conveyance, or there will need to be a floodway revision.
11.4 Evaluating “No-Rise” Analyses Submitted by Engineers
The community must prohibit development in the floodway unless it has been demonstrated
through hydrologic and hydraulic analyses performed in accordance with standard engineering
practice that the proposed encroachment would not result in any increase in flood levels within
the community during occurrence of the base flood discharge. It is the community’s responsibility
to make the determination that a development in the floodway will not cause any increase in flood
stage. You cannot depend solely on registered professional engineer’s no-rise certification and
must review and approve the submission.
A certification by a registered professional engineer does not constitute a warranty or guarantee
of performance, expressed or implied. Certification of data is a statement that the data is accurate
to the best of the certifier’s knowledge. Certification of an analysis is a statement that the analysis
has been performed correctly and in accordance with sound engineering practice. However, not
all engineers are equally skilled or experienced in performing technical analyses and there is room
for disagreements as to what constitutes standard engineering practice. Remember the
registered professional engineer works for the permit applicant and not the community. The no
rise certification is a valuable piece of information that you can use to help make your
determination, but you are not obligated to accept the no-rise certification if you have reason to
believe that it is not done correctly.
Communities that have city or county engineering departments or that contract for these services
are encouraged to develop their own in-house engineering capability to evaluate proposals for
floodway development and review no-rise certifications. If your community is part of a flood
control or water management district, they may be willing to provide this service for their local
governments. Some states that have their own state floodplain management regulations or that
maintain engineering staffs that conduct Flood Insurance Studies may also be willing to perform
this service for communities. If the development requires a floodway revision and you wish to
approve the development, forward the revision request to FEMA and it will do the review as part
of processing the request.
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Figure 11-2. Example of a No-Rise Certificate.
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Communities should look at the following when reviewing no-rise certifications.
The registered professional engineer should be experienced in conducting hydrologic and
hydraulic studies. You do not have to accept a certification if you do not feel that the
engineer is qualified to conduct the analysis.
The analyses must be conducted using the hydraulic model that was used to develop the
FIS if it is still available.
The analyses should be consistent with basic hydraulic principles. For example, there
needs to be smooth transitions in flood flows between cross sections. Abrupt changes in
floodway width for example should be avoided.
If the development is located between existing cross sections, additional cross sections
must have been surveyed at the site of the development to accurately model the impacts
of the development.
The analysis should not include unrealistic land use or hydraulic assumptions. For
example, if the analysis assumes that roughness coefficients used in the original FIS are
changed, the new roughness coefficients must reflect what is actually on the ground.
There should be no cumulative impacts if other property owners undertake similar
developments. It is important that there really is no increase in flood stage due to the
development.
If the no-rise analysis depends on adding additional flow areas to compensate for the
impacts of an encroachment, you must ensure that the flow area will be available in
perpetuity and that the floodwaters can get to and use that flow area. You will want to
require the applicant to apply for a floodway revision and adopt the revised floodway as
part of your ordinance.
Again, if you have doubts about the submission, contact your state or FEMA Regional Office for
assistance (http://www.fema.gov/business/nfip/nfip_regions.shtm).
If the analysis depends on a change in floodway boundaries to achieve “no-rise” and a floodway
revision will be required see Section 7, Obtaining a Revision to Floodway Boundaries. If you
approve the request and forward a request for a floodway revision to FEMA, FEMA will review
the hydraulic analysis when it reviews the request.
Generally, you must maintain documentation in your files of the hydraulic analysis, the no-rise
certification, and your determination indefinitely. FEMA or your state will ask to see the
documentation on your next Community Assistance Visit (CAV), and you will need the
documentation if your floodway is ever revised.
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12.0 Encroachment Requirements for Rivers and Streams without
Floodways
FEMA may also issue a FIRM that include rivers or streams where FEMA has conducted a
detailed study and established base flood elevations, but not designated a floodway. Generally,
these Studies are conducted in less densely populated areas where it is difficult to justify the
expense of conducting an engineering study that would include a floodway. These areas are
subject to the requirements at 44 CFR 60.3(c)(10) which requires a hydraulic analysis to ensure
that each development in the floodplain does not increase base flood levels by more than one
foot at any point in the community. The requirement at 44 CFR 60.3(c)(10) essentially applies
the same standard to these areas as would apply if a floodway were designated (the maximum
one foot rise in flood stage). The main difference is that the hydraulic analyses are conducted on
a case-by-case basis for each proposed development in the floodplain. Most communities pass
on the cost of performing this analysis to the permit applicant. The advantage of having a
floodway designated is that is that the community can review and permit development outside of
the floodway without requiring a hydraulic analysis and without passing the costs of that analysis
on to the permit applicant.
The requirement in 63.3(c)(10) only applies along rivers, streams, and other watercourses where
FEMA has provided base flood elevations. The requirement does not apply along lakes, bays
and estuaries, and the ocean coast. Generally, this type of data is provided as interim data and
the intent is to eventually re-map these areas to add floodways when funding becomes available
and the amount of development warrants the added cost to develop floodways.
Sometimes a decision is made not to designate a floodway on a stream because hydraulic
conditions on the river or stream do not lend themselves to modeling a floodway using standard
methodologies. Generally, FEMA, the state, and the community agree to an alternative
management scheme for the stream that achieves the same purpose as designating a floodway
or performing an encroachment analyses under 60.3(c)(10).
44 CFR 60.3(c)(10): Require until a regulatory floodway is
designated, that no new construction, substantial
improvements, or other development (including fill) shall be
permitted within zones A1-30 and AE on the community’s
FIRM, unless it is demonstrated that the cumulative effect
of the proposed development when combined with all other
existing and anticipated development, will not increase the
water surface elevation of the base flood more than one
foot at any point within the community.
12.1 Ways to Meet the 60.3(c)(10) Requirement
Section 60.3(c)(10) of NFIP regulations requires a hydraulic analysis to ensure that each
development in the floodplain does not increase base flood levels by more than one foot at any
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point in the community. One of the concerns that have been expressed about implementing the
requirement has been the cost of performing a hydraulic analyses for a small development such
as a single home. The costs of this analysis must be considered as part of the cost of developing
in the floodplain. The potential adverse impacts of development in the floodplain on upstream
and adjacent property owners can be significant and must be evaluated before the development
is allowed to occur. However, there are several ways a community can avoid or minimize these
costs:
Stay out of the floodplain entirely. Usually limited detail studies without floodways are
provided in rural areas or less densely populated areas where parcels are large and there
is a choice of building sites. In these cases, it is often in everyone’s best interest to design
the development so that the building sites are located outside of the floodplain. The
floodplain is preserved, and the permit applicant avoids the added costs of performing the
hydraulic analysis and of developing in the floodplain.
Limit development to backwater areas. It may also be possible to limit the development
to backwater areas that are not effective flow areas. Most floodplains have irregular
boundaries and include backwater areas that provide storage of floodwaters but play little
or no role in the conveyance of floodwaters. The velocity of floodwaters in these areas
may be zero or close to zero. There may also be floodplain areas that are separated from
the river or stream by a railroad or road embankment or a substantial levee that is at or
near the base flood elevation that parallels the river or stream. Areas behind these
obstructions also may not convey flood flows. These areas are not taken into account as
flow areas when the hydraulic model is developed of the floodplain. Development of these
areas will not increase flood stages. A qualified engineer can apply basic hydraulic
principles to identify these areas. The remainder of the floodplain is sometimes referred
to as a natural floodway.
Establish setbacks: Finally, it may be possible to develop a standard setback or an
algorithm for establishing setbacks along smaller streams in your community that would
serve the same purpose as 44 CFR 60.3(c)(10). You may already have adopted a setback
to preserve a natural stream buffer to protect water quality. Back-up your setback or
algorithm with engineering calculations to show that development will cause no more than
a one foot rise in flood stage. Be conservative. Test the setback or algorithm on a
reasonable number of cross-sections given the variety of stream conditions in your
community. If you choose this alternative, check with your state or FEMA Regional Office
first.
If you adopt either the second or third alternative and feel that permit applicants may challenge
your setbacks or other requirements, you can always allow the applicant the option of hiring an
engineer and submitting a (c)(10) analysis if they disagree. Most permit applicants are likely to
comply with your requirement as long as it is reasonable rather than to go to the expense of
paying for a hydraulic analysis.
12.2 Performing a 60.3(c)(10) Analysis
In those floodplains where FEMA has provided the community with base flood elevations, but no
floodway, the community must prohibit development unless it is demonstrated that the cumulative
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effect of the proposed development when combined with all other existing and anticipated
development, will not increase the water surface elevation of the base flood more than one foot
at any point within the community.
When evaluating the proposed development, you must assume that other like situated property
owners will want to develop their properties in the same manner as the permit applicant and that
eventually their properties will be developed. You must take their rights to develop into account
when evaluating a development to determine if it will cause no more than a one foot increase in
flood stage for the base flood. For example, if the permit applicant wants to build a house on fill
that extends 100 feet into the floodplain, you must assume that the property owners across the
stream encroach into the floodplain an equal amount. You must also make the same assumption
for upstream and downstream property owners on both sides of the river or stream. You are in
effect developing a floodway for that reach of stream. You need to extend your hydraulic analysis
far enough upstream and downstream to capture the cumulative impacts of all of this
development.
13.0 Obtaining a Revision to Floodway Boundaries
Generally, you must apply for and obtain a floodway revision from FEMA any time you want to
make a change in the FEMA-designated floodway boundaries even if the change is so small that
it would not be visible on your FIRM. Applicants for floodway revisions usually want to narrow the
width of the floodway or shift the location or alignment of the floodway to allow for a development.
Procedures for obtaining a floodway revision can be found in NFIP regulations at 44 CFR 65.7
Floodway Revisions.
Requests for floodway revisions must come from the community. It is your floodway that you
have legally adopted as part of your floodplain management ordinance. You probably held a
public hearing and met other due process requirements when you designated your floodway and
usually will have to meet the same requirements to adopt a floodway revision. You are not
obligated to revise your floodway merely because a permit applicant can demonstrate that it is
possible to narrow the floodway or change the floodway alignment. Remember that when you
revise a floodway boundary, you may impact on other property owners in your community. They
usually will have an interest in maintaining the current floodway alignment and must be notified
before you propose a Floodway Revision to FEMA.
13.1 Procedures for Applying for a Floodway Revision
Applications for floodway revisions are submitted using FEMA’s MT-2 Forms. The MT-2 Forms
and the accompanying instructions can be downloaded from FEMA’s web site
).
(http://www.fema.gov/plan/prevent/fhm/dl_mt-2.shtm
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44 CFR 65.7 Floodway Revisions. (a) General:
Floodway data is developed as part of FEMA Flood
Insurance Studies and is utilized by communities to select
and adopt floodways as part of the floodplain management
program required by Sec. 60.3 of this subchapter. When it
has been determined by the community that no practicable
alternatives exist to revising the boundaries of its previously
adopted floodway, the procedures below shall be followed.
You are under no obligation to request a floodway revision under 44 CFR 65.7 just because a
developer wants one. It is your floodway that you have adopted in accordance with your due
process requirements and you as a community must approve the proposal and submit it to FEMA.
Remember you are required to evaluate alternatives to the development that would meet the
requirements of your floodplain management ordinance and demonstrate that these alternatives
are not feasible before a LOMR will be issued by FEMA. In most situations there will be
alternatives that do not require encroachments into your floodway or floodplain that would not
require a floodway revision.
You will be required to submit evidence that all affected property owners and communities have
been notified of your intent to revise the floodway to assure that they are aware of potential
adverse impacts of the revision. Your community will also have to find that the revision and the
proposed project meet or are designed to meet all community floodplain management
requirements and that all necessary federal, state, and local permits have been or will be obtained.
The most commonly required federal permits are wetlands permits under Section 404 of the Clean
Water Act of 1972 and incidental take permits under Section 10 of the Endangered Species Act
of 1972. If the floodway revision is approved by FEMA, you will be required to adopt the revised
floodway as part of your floodplain management ordinance and use the revised floodway to
regulate future development.
The procedure for applying for a floodway revision requires a hydraulic analysis similar to that
required to demonstrate that a development would cause no-rise in the elevation of the base
flood. The main difference is that instead of evaluating the impacts of a development in the
floodway on the base flood elevation, the hydraulic analysis is instead demonstrating that the
proposed revised floodway including any modifications that have been made to the channel and
overbank areas within the revised floodway will carry the base flood without increasing the water
surface elevation of that flood more than one foot at any point in the community. This is the same
standard used to designate the floodway that is being revised.
13.2 Development Proposals that Exceed the One Foot Standard
There are limited situations where it may be necessary to allow development in the floodway or
the floodplain that would result in increases in the base flood elevation greater than that generally
allowed by NFIP minimum criteria. This could include:
A proposal for development in the floodway that would cause an increase in the base flood
elevation.
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A request for a revision to floodway boundaries that would result in a floodway that would
result in greater than the allowable one foot surcharge.
A proposal for development in a floodplain where no floodway has been designated that
would cause greater than a one foot increase in flood stage.
Generally, this type of development is discouraged. Designation of the floodway can already
cause up to a one foot increase in flood stage and even this one foot increase can substantially
increase upstream flood damages.
There are situations where it may be in the public interest to allow this development if no existing
buildings are impacted and future buildings are elevated or floodproofed to the new base flood
elevations. The procedure for obtaining a FIRM and floodway revision to allow this type of
development has been established at 44 CFR 65.12 of NFIP regulations. Section 65.12 was
developed to provide a mechanism to address several situations where it was thought to be in
the public interest to allow development in the floodplain that would otherwise violate the
provisions of the community’s floodplain management ordinance. These situations include:
Construction or increase in height of a dam or other water control structure particularly
when it would reduce overall flood damages. Without the procedure at Section 65.12 this
type of development would not be permitted under the community’s floodplain
management ordinance.
Construction or replacement of roads or bridges that cross the floodplain. In situations
where no existing development is impacted by the increase in flood stage there may be
considerable cost savings in building a bridge with a smaller waterway opening.
Other developments that have a net public benefit where there are no practicable
alternative actions that would comply with the community’s floodplain management
requirements.
The procedure can only be used in situations where no existing structures will be impacted by the
increase in the base flood elevation and only if all affected property owners are notified of the
proposed revision. If FEMA approves the revised floodway, the community must adopt the
revised floodway and higher base flood elevations and use them to regulate all future
development. Often agencies proposing to construct such facilities are willing to purchase and
relocate impacted buildings and purchase flowage easements to mitigate the impacts of the
increased base flood elevations.
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44 CFR 60.3(c)(13): Notwithstanding any other provisions
of Sec. 60.3, a community may approve certain
development in Zones A1-30, AE, and AH, on the
community’s FIRM which increase the water surface
elevation of the base flood by more than one foot, provided
that the community applies for a conditional FIRM revision,
fulfills the requirements for such a revision as established
under the provisions of Sec. 65.12, and receives the
approval of the Administrator.
44 CFR 60.3(d)(4): Notwithstanding any other provisions
of Sec. 60.3, a community may permit encroachments
within the adopted regulatory floodway that would increase
in base flood elevations, provided that the community
applies for a conditional FIRM and floodway revision, fulfills
the requirements for such a revision as established under
the provisions of Sec. 65.12, and receives the approval of
the Administrator.
Guidance for meeting the requirements of Section 65.12 can be found in the MT-2 Forms and
Instructions and in Appendix C. A community may allow this type of development only if applies
for and obtains a conditional FIRM and floodway revision and meets specific requirements in
Section 65.12. A FIRM revision will be required to reflect any increase in base flood elevations
due to the development. A floodway revision is required if there is a change in floodway
boundaries. Once the community obtains approval of the FIRM and floodway revision, it must
adopt the higher base flood elevations and revised floodway prior to permitting the development.
13.3 Meeting the Requirements of 44 CFR 65.12
Prior to permitting a proposed development in the floodway that would cause an increase in the
base flood elevation, a request for a revision to floodway boundaries that would result in greater
than the allowable one foot surcharge, or proposed development in a floodplain where no
floodway has been designated that would cause greater than a one foot increase in flood stage
the community must apply for and obtain approval from FEMA of a conditional FIRM and floodway
revision.
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44 CFR 65.12 Revision of flood insurance rate maps to
reflect base flood elevations caused by proposed
encroachments.
(a) When a community proposes to permit encroachments
on the floodplain when a regulatory floodway has not been
adopted or to permit encroachments upon an adopted
regulatory floodway which will cause base flood elevations
increases in excess of that permitted under paragraphs
(c)(10) or (d)(3) of s.60.3 of this subchapter, the community
shall apply to the Administrator for conditional approval of
such action prior to permitting the encroachments to occur
and shall submit the following as part of the application:
The requirements for obtaining conditional approval are found in 44 CFR 65.12. The community
must:
Evaluate alternatives to the development that would meet the requirements of 60.3(c)(10)
or (d)(3) and demonstrate that these alternatives are not feasible.
Provide individual notice to each property owner explaining the impact of the proposed
action on their property.
Obtain concurrence of the Chief Executive Officer of any other community impacted by
the proposed action.
Certify that no structures would be impacted by the increased base flood elevations.
Once the conditional map change has been approved by FEMA the community must adopt the
increased base flood elevations and revised floodway prior to permitting the proposed action. The
increased base flood elevations and revised floodway become part of the ordinance and apply to
all future development in the community.
You are under no obligation to request a floodway revision under 44 CFR 65.12 just because a
developer wants one. It is your floodway that you have adopted in accordance with your due
process requirements and you as a community must approve the proposal and submit it to FEMA.
Remember you will be required to evaluate alternatives to the development that would meet the
requirements of your floodplain management and demonstrate that these alternatives are not
feasible before a CLOMR will be issued by FEMA. In most situations there will be alternatives
that do not require encroachments into your floodway or floodplain that would exceed those
permitted in your floodplain management ordinance.
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14.0 Alterations and Relocations of Watercourses
Communities that participate in the NFIP are also required to assure that flood carrying capacity
of an altered or relocated watercourse in a floodplain is maintained. This requirement applies in
Zone A where FEMA has not provided base flood elevations as well as in Zones AE, A1-30, AO
and AH which have been studied in detail. In order to meet this requirement, communities must
assure that:
Any altered or relocated watercourse has the same or greater flood carrying capacity as
it did before the alteration occurred, and
Once the watercourse has been altered or relocated, the community has an affirmative
responsibility to assure that it is properly maintained.
The community is also responsible for notifying adjacent communities and the state coordinating
office prior to altering or relocating a watercourse and providing FEMA with a copy of this
notification.
44 CFR 60.3(b):
(6) Notify, in riverine situations, adjacent communities and
the State Coordinating Office prior to any alteration or
relocation of a watercourse, and submit copies of such
notifications to the Administrator;
(7) Assure that the flood carrying capacity within the altered
or relocated portion of any watercourse is maintained;
14.1 Definition of Watercourse
Watercourse is not defined in NFIP regulations, but generally means the channel of a river, stream
or drainage way and not the adjacent overbank areas. Placement of fill in the overbank areas
only and outside of the channel is not an alteration or relocation of a watercourse. The overbank
areas are addressed under the NFIP floodway requirements. Watercourses include not only
rivers or streams that are the source of flooding used to determine the base flood and the
floodplain boundaries, but also smaller streams, drainage ways and ditches within the floodplain
that could flood during smaller more frequent events.
14.2 Application
The requirement to maintain the carrying capacity of altered or relocated watercourses applies to
watercourses in all mapped floodplains. In a Zone A where no base flood elevations have been
provided by FEMA, the requirements are particularly important because there are no floodways
designated and no other requirements that would preserve the capacity of the floodplain to convey
floodwaters. Preserving the capacity of the watercourse to convey floodwaters will help prevent
flooding from becoming worse as the area develops. Historically, the failure to maintain the
carrying capacity of altered relocated channels has created numerous flood problems. For
example, it was common practice to force a natural stream into a pipe or culvert when developing
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an industrial area or a subdivision. Frequently these pipes or culverts did not have the capacity
to pass the 1% chance flood or even much more frequent floods. The result was chronic flooding,
repetitive flood losses, and eventually costly corrective measures.
Once FEMA provides a community with base flood elevations and a floodway is designated the
requirements continue to apply to the channel of the river or stream. The floodway designation
will prevent encroachments in the floodplain that cause more than a one foot increase in flood
stage while the (b)(6) and (b)(7) requirements will protect the capacity of the channel of river or
stream to convey floodwaters. The (b)(6) and (b)(7) requirements also will continue to apply to
watercourses such as smaller tributary streams and drainage ways within the floodplain even
though they are not the flooding source that produces the base flood elevation.
Communities are not required to maintain natural streams or channels and watercourses that
were altered or relocated before the community joined the NFIP. Natural streams and
watercourses that were altered or relocated before the community joined the NFIP are treated as
existing conditions that are taken into account when the floodplain is mapped by FEMA. FEMA
recognizes that maintaining natural streams can be costly to the community and often raises
environmental issues. Watercourses that were altered or relocated prior to the community’s
participation in the NFIP can also be costly to maintain and the community may not have the legal
authority to undertake or require their maintenance. However, if these watercourses do silt in or
become clogged with debris or other obstructions, FEMA will eventually have to re-map these
areas to reflect the increased flood hazard. The floodplain will likely become larger and the base
flood elevation will increase. It is usually in the best interests of communities to maintain these
pre-existing altered or relocated channels even though it is not required by FEMA to ensure that
flooding does not increase and to avoid the need for this remapping.
14.3 Maintaining the Carrying Capacity of the Watercourse
Communities must assure that the carrying capacity of the altered or relocate watercourse is
maintained. This means that the carrying capacity of the altered or relocated channel must be
the same or greater than the original watercourse. The community will have to undertake some
kind of analysis to assure that this occurs.
In undeveloped areas designated as Zone A where FEMA has not conducted a detailed
engineering study and not developed base flood elevations, this analysis can be as simple as the
community engineer reviewing the proposal and determining that:
The channel size and cross section are as big, and the channel is as straight as the original
watercourse and that there are smooth hydraulic transitions into and out of the altered or
relocated portion of the watercourse.
The channel sides and bottom are of the same or similar materials to the original
watercourse and that the roughness coefficient is roughly the same.
If there are substantial differences between the altered and relocated channel and the original
watercourse it may be necessary to require that the permit applicant submit a hydraulic analysis
by a registered professional engineer.
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In developed areas a detailed hydraulic analysis will usually be necessary to assure that the
carrying capacity of the watercourse is maintained because of the potential for increasing flood
damages to existing buildings. If the area has a floodway designated, this can be done as part of
the hydraulic analyses necessary to meet floodway requirements.
If you choose to enlarge a watercourse you may impact on downstream peak flood discharges.
The larger channel will carry more floodwaters and depending on the watershed may increase or
decrease these peak discharges. You should consider requiring the permit applicant to provide
an analysis assessing these impacts before you approve the development.
14.4 Maintaining the Altered or Relocated Portion of the Watercourse
Once a watercourse is altered or relocated an artificial condition is created. If the watercourse is
not maintained, erosion of the banks and sedimentation could occur decreasing the capacity of
the channel to carry flood flows. Altered and relocated rivers or streams will often meander and
try to return to their old location. In addition, vegetation can grow choking the altered or relocated
channel. Any benefits in reducing flood hazards from the altered or relocated channel will be lost
and flood hazards could increase. Figure 14-1 shows a constructed channel that is overgrown
with vegetation and for which the conveyance is significantly reduced.
Figure 14-1. Picture of a constructed channel in Arizona that is overgrown with vegetation
(from U.S. Geological Survey Scientific Investigations Report 2006-5108).
As a result, it is critical that any altered or relocated channel be maintained. There are two ways
that this can be done. First, the community can formally assume ownership or responsibility for
the maintenance of the channel and obtain from the permit applicant any necessary easements
or other permissions necessary to conduct the maintenance. Second, the community can
negotiate an enforceable maintenance agreement with the owner of the watercourse to assure
that the watercourse is maintained. Whichever alternative is chosen the community will have to
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periodically inspect the watercourse. When maintenance is required, the community will either
have to conduct the maintenance or require the owner of the watercourse to conduct the
maintenance.
If a community requests that FEMA revise its FIRM based on an altered or relocated watercourse,
FEMA will require you to submit a maintenance agreement prior to issuing a Letter of Map
Revision (LOMR) or physical map revision. If the channel is not maintained, FEMA can rescind
the LOMR, revise the FIRM to show the increased flood hazard, or initiate an enforcement action
against the community.
14.5 NFIP Community Rating System (CRS) Credits for Drainage System
Maintenance
The NFIP provides credit under its Community Rating System (CRS) for communities that have
Drainage System Maintenance programs that meet CRS requirements. The CRS provides
discounts on flood insurance premiums in communities that undertake floodplain management
activities that go beyond the minimum requirements for community participation in the NFIP.
For the purposes of CRS, a community’s drainage system includes those natural and man-made
drainage ways and channels, storm sewers and ditches, and detention and retention basins that
must be maintained in order to prevent damages to buildings during smaller more frequent storms.
Drainage System Maintenance credits are provided for communities that establish and implement
programs to systematically inspect their drainage systems, including all channels and debris
basins, and remove debris and correct any drainage problems they encounter. This credit applies
to all natural and man-made watercourses that are part of the community’s drainage system, not
just those that have been altered or relocate since the community joined the NFIP.
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Related Templates associated
with this Guidance
Note:
The following templates will be a tool to help practitioners comply with the guidance contained in
this document and will help with overall program consistency. Once they have been reviewed
and comments have been addressed, the templates will be stored individually on the fema.gov
G&S web page under the “Templates and Other Resources” link (http://www.fema.gov/media-
library/assets/documents/32786?id=7577). They are merely provided here to aid in the
consolidation of review comments to one document.
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11.3How a No-Rise Certification is Developed
NFIP minimum criteria prohibit encroachments in the adopted regulatory floodway unless it has
been demonstrated through hydrologic and hydraulic analyses performed in accordance with
standard engineering practice that the encroachment will not cause any increase in flood levels
in the community during the base flood discharge. FEMA defines “any” as meaning a zero
increase. It does not mean that you can allow a .1 foot or even a .01 foot increase – it means
0.00 feet. Otherwise the cumulative effects of all of the developments in the floodway could
significantly increase flood stages. There should be no cumulative effects since the permissible
increase for any single development is zero.
This hydrologic and hydraulic analysis is commonly called a no-rise or zero-rise analysis and
results in a no-rise certification. A few states and communities perform the no-rise analysis
themselves, but most require the permit applicant to hire a qualified registered profession
engineer to perform the analysis and provide the no-rise certification.
Some communities require that the registered professional engineer submit the no-rise certificate
on a form such as the example in Figure 11-2. Other communities allow the engineer to submit
the certification in a letter. Either way is acceptable provided that all of the necessary information
is included. The no-rise certification must be accompanied by documentation to support the
finding that there will be no increase in flood stage including the results of the hydraulic study.
Generally, the process for conducting the hydraulic analyses is the same as that used for applying
for a FIRM or floodway revision (see Section 7).
The registered professional engineer obtains a copy of the model used to develop the
effective FIS from FEMA. For information on how to obtain copies of the effective
model, see FEMA’s Internet site at http://www.fema.gov/plan/prevent/fhm/st_order.shtm.
The engineer duplicates the results of the effective model (called the Duplicative Effective
Model).
The engineer makes any corrections to the effective model (called the Corrected Effective
Model) such as technical errors in the effective modeling or the inclusion of any floodplain
changes that occurred prior to the date of the effective model.
The engineer develops a model for existing conditions that reflects any modifications that
have occurred within the floodplain since the date of the effective model but prior to the
proposed development (called the Existing Conditions Model). Generally, one or more
additional cross sections will be necessary to model the impacts of the proposed
development and any modifications that are made to the channel or overbank areas to
compensate for any loss of conveyance.
The engineer modifies the Existing Conditions model to reflect the proposed development
at the new cross sections while retaining the currently adopted floodway widths (called the
Proposed Conditions Model).
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The engineer compares the results of the Proposed Conditions Model to the Effective
Model or Corrected Effective Model to determine if there will be an increase in elevation
of the base flood or floodway elevations at any existing or new cross section.
If there will not be an increase in either of the elevations, the engineer can prepare and submit
the no-rise certification and the supporting technical documentation to the community (Figure 11-
2). If there will be an increase, the development will have to be redesigned to avoid the floodway,
compensation provided for the loss of conveyance, or there will need to be a floodway revision.
11.4 Evaluating “No-Rise” Analyses Submitted by Engineers
The community must prohibit development in the floodway unless it has been demonstrated
through hydrologic and hydraulic analyses performed in accordance with standard engineering
practice that the proposed encroachment would not result in any increase in flood levels within
the community during occurrence of the base flood discharge. It is the community’s responsibility
to make the determination that a development in the floodway will not cause any increase in flood
stage. You cannot depend solely on registered professional engineer’s no-rise certification and
must review and approve the submission.
A certification by a registered professional engineer does not constitute a warranty or guarantee
of performance, expressed or implied. Certification of data is a statement that the data is accurate
to the best of the certifier’s knowledge. Certification of an analysis is a statement that the analysis
has been performed correctly and in accordance with sound engineering practice. However, not
all engineers are equally skilled or experienced in performing technical analyses and there is room
for disagreements as to what constitutes standard engineering practice. Remember the
registered professional engineer works for the permit applicant and not the community. The no
rise certification is a valuable piece of information that you can use to help make your
determination, but you are not obligated to accept the no-rise certification if you have reason to
believe that it is not done correctly.
Communities that have city or county engineering departments or that contract for these services
are encouraged to develop their own in-house engineering capability to evaluate proposals for
floodway development and review no-rise certifications. If your community is part of a flood
control or water management district, they may be willing to provide this service for their local
governments. Some states that have their own state floodplain management regulations or that
maintain engineering staffs that conduct Flood Insurance Studies may also be willing to perform
this service for communities. If the development requires a floodway revision and you wish to
approve the development, forward the revision request to FEMA and it will do the review as part
of processing the request.
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Figure 11-2. Example of a No-Rise Certificate.
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Communities should look at the following when reviewing no-rise certifications.
The registered professional engineer should be experienced in conducting hydrologic and
hydraulic studies. You do not have to accept a certification if you do not feel that the
engineer is qualified to conduct the analysis.
The analyses must be conducted using the hydraulic model that was used to develop the
FIS if it is still available.
The analyses should be consistent with basic hydraulic principles. For example, there
needs to be smooth transitions in flood flows between cross sections. Abrupt changes in
floodway width for example should be avoided.
If the development is located between existing cross sections, additional cross sections
must have been surveyed at the site of the development to accurately model the impacts
of the development.
The analysis should not include unrealistic land use or hydraulic assumptions. For
example, if the analysis assumes that roughness coefficients used in the original FIS are
changed, the new roughness coefficients must reflect what is actually on the ground.
There should be no cumulative impacts if other property owners undertake similar
developments. It is important that there really is no increase in flood stage due to the
development.
If the no-rise analysis depends on adding additional flow areas to compensate for the
impacts of an encroachment, you must ensure that the flow area will be available in
perpetuity and that the floodwaters can get to and use that flow area. You will want to
require the applicant to apply for a floodway revision and adopt the revised floodway as
part of your ordinance.
Again, if you have doubts about the submission, contact your state or FEMA Regional Office for
assistance (http://www.fema.gov/business/nfip/nfip_regions.shtm).
If the analysis depends on a change in floodway boundaries to achieve “no-rise” and a floodway
revision will be required see Section 7, Obtaining a Revision to Floodway Boundaries. If you
approve the request and forward a request for a floodway revision to FEMA, FEMA will review
the hydraulic analysis when it reviews the request.
Generally, you must maintain documentation in your files of the hydraulic analysis, the no-rise
certification, and your determination indefinitely. FEMA or your state will ask to see the
documentation on your next Community Assistance Visit (CAV), and you will need the
documentation if your floodway is ever revised.
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12.0 Encroachment Requirements for Rivers and Streams without
Floodways
FEMA may also issue a FIRM that include rivers or streams where FEMA has conducted a
detailed study and established base flood elevations, but not designated a floodway. Generally,
these Studies are conducted in less densely populated areas where it is difficult to justify the
expense of conducting an engineering study that would include a floodway. These areas are
subject to the requirements at 44 CFR 60.3(c)(10) which requires a hydraulic analysis to ensure
that each development in the floodplain does not increase base flood levels by more than one
foot at any point in the community. The requirement at 44 CFR 60.3(c)(10) essentially applies
the same standard to these areas as would apply if a floodway were designated (the maximum
one foot rise in flood stage). The main difference is that the hydraulic analyses are conducted on
a case-by-case basis for each proposed development in the floodplain. Most communities pass
on the cost of performing this analysis to the permit applicant. The advantage of having a
floodway designated is that is that the community can review and permit development outside of
the floodway without requiring a hydraulic analysis and without passing the costs of that analysis
on to the permit applicant.
The requirement in 63.3(c)(10) only applies along rivers, streams, and other watercourses where
FEMA has provided base flood elevations. The requirement does not apply along lakes, bays
and estuaries, and the ocean coast. Generally, this type of data is provided as interim data and
the intent is to eventually re-map these areas to add floodways when funding becomes available
and the amount of development warrants the added cost to develop floodways.
Sometimes a decision is made not to designate a floodway on a stream because hydraulic
conditions on the river or stream do not lend themselves to modeling a floodway using standard
methodologies. Generally, FEMA, the state, and the community agree to an alternative
management scheme for the stream that achieves the same purpose as designating a floodway
or performing an encroachment analyses under 60.3(c)(10).
44 CFR 60.3(c)(10): Require until a regulatory floodway is
designated, that no new construction, substantial
improvements, or other development (including fill) shall be
permitted within zones A1-30 and AE on the community’s
FIRM, unless it is demonstrated that the cumulative effect
of the proposed development when combined with all other
existing and anticipated development, will not increase the
water surface elevation of the base flood more than one
foot at any point within the community.
12.1 Ways to Meet the 60.3(c)(10) Requirement
Section 60.3(c)(10) of NFIP regulations requires a hydraulic analysis to ensure that each
development in the floodplain does not increase base flood levels by more than one foot at any
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point in the community. One of the concerns that have been expressed about implementing the
requirement has been the cost of performing a hydraulic analyses for a small development such
as a single home. The costs of this analysis must be considered as part of the cost of developing
in the floodplain. The potential adverse impacts of development in the floodplain on upstream
and adjacent property owners can be significant and must be evaluated before the development
is allowed to occur. However, there are several ways a community can avoid or minimize these
costs:
Stay out of the floodplain entirely. Usually limited detail studies without floodways are
provided in rural areas or less densely populated areas where parcels are large and there
is a choice of building sites. In these cases, it is often in everyone’s best interest to design
the development so that the building sites are located outside of the floodplain. The
floodplain is preserved, and the permit applicant avoids the added costs of performing the
hydraulic analysis and of developing in the floodplain.
Limit development to backwater areas. It may also be possible to limit the development
to backwater areas that are not effective flow areas. Most floodplains have irregular
boundaries and include backwater areas that provide storage of floodwaters but play little
or no role in the conveyance of floodwaters. The velocity of floodwaters in these areas
may be zero or close to zero. There may also be floodplain areas that are separated from
the river or stream by a railroad or road embankment or a substantial levee that is at or
near the base flood elevation that parallels the river or stream. Areas behind these
obstructions also may not convey flood flows. These areas are not taken into account as
flow areas when the hydraulic model is developed of the floodplain. Development of these
areas will not increase flood stages. A qualified engineer can apply basic hydraulic
principles to identify these areas. The remainder of the floodplain is sometimes referred
to as a natural floodway.
Establish setbacks: Finally, it may be possible to develop a standard setback or an
algorithm for establishing setbacks along smaller streams in your community that would
serve the same purpose as 44 CFR 60.3(c)(10). You may already have adopted a setback
to preserve a natural stream buffer to protect water quality. Back-up your setback or
algorithm with engineering calculations to show that development will cause no more than
a one foot rise in flood stage. Be conservative. Test the setback or algorithm on a
reasonable number of cross-sections given the variety of stream conditions in your
community. If you choose this alternative, check with your state or FEMA Regional Office
first.
If you adopt either the second or third alternative and feel that permit applicants may challenge
your setbacks or other requirements, you can always allow the applicant the option of hiring an
engineer and submitting a (c)(10) analysis if they disagree. Most permit applicants are likely to
comply with your requirement as long as it is reasonable rather than to go to the expense of
paying for a hydraulic analysis.
12.2 Performing a 60.3(c)(10) Analysis
In those floodplains where FEMA has provided the community with base flood elevations, but no
floodway, the community must prohibit development unless it is demonstrated that the cumulative
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effect of the proposed development when combined with all other existing and anticipated
development, will not increase the water surface elevation of the base flood more than one foot
at any point within the community.
When evaluating the proposed development, you must assume that other like situated property
owners will want to develop their properties in the same manner as the permit applicant and that
eventually their properties will be developed. You must take their rights to develop into account
when evaluating a development to determine if it will cause no more than a one foot increase in
flood stage for the base flood. For example, if the permit applicant wants to build a house on fill
that extends 100 feet into the floodplain, you must assume that the property owners across the
stream encroach into the floodplain an equal amount. You must also make the same assumption
for upstream and downstream property owners on both sides of the river or stream. You are in
effect developing a floodway for that reach of stream. You need to extend your hydraulic analysis
far enough upstream and downstream to capture the cumulative impacts of all of this
development.
13.0 Obtaining a Revision to Floodway Boundaries
Generally, you must apply for and obtain a floodway revision from FEMA any time you want to
make a change in the FEMA-designated floodway boundaries even if the change is so small that
it would not be visible on your FIRM. Applicants for floodway revisions usually want to narrow the
width of the floodway or shift the location or alignment of the floodway to allow for a development.
Procedures for obtaining a floodway revision can be found in NFIP regulations at 44 CFR 65.7
Floodway Revisions.
Requests for floodway revisions must come from the community. It is your floodway that you
have legally adopted as part of your floodplain management ordinance. You probably held a
public hearing and met other due process requirements when you designated your floodway and
usually will have to meet the same requirements to adopt a floodway revision. You are not
obligated to revise your floodway merely because a permit applicant can demonstrate that it is
possible to narrow the floodway or change the floodway alignment. Remember that when you
revise a floodway boundary, you may impact on other property owners in your community. They
usually will have an interest in maintaining the current floodway alignment and must be notified
before you propose a Floodway Revision to FEMA.
13.1 Procedures for Applying for a Floodway Revision
Applications for floodway revisions are submitted using FEMA’s MT-2 Forms. The MT-2 Forms
and the accompanying instructions can be downloaded from FEMA’s web site
).
(http://www.fema.gov/plan/prevent/fhm/dl_mt-2.shtm
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44 CFR 65.7 Floodway Revisions. (a) General:
Floodway data is developed as part of FEMA Flood
Insurance Studies and is utilized by communities to select
and adopt floodways as part of the floodplain management
program required by Sec. 60.3 of this subchapter. When it
has been determined by the community that no practicable
alternatives exist to revising the boundaries of its previously
adopted floodway, the procedures below shall be followed.
You are under no obligation to request a floodway revision under 44 CFR 65.7 just because a
developer wants one. It is your floodway that you have adopted in accordance with your due
process requirements and you as a community must approve the proposal and submit it to FEMA.
Remember you are required to evaluate alternatives to the development that would meet the
requirements of your floodplain management ordinance and demonstrate that these alternatives
are not feasible before a LOMR will be issued by FEMA. In most situations there will be
alternatives that do not require encroachments into your floodway or floodplain that would not
require a floodway revision.
You will be required to submit evidence that all affected property owners and communities have
been notified of your intent to revise the floodway to assure that they are aware of potential
adverse impacts of the revision. Your community will also have to find that the revision and the
proposed project meet or are designed to meet all community floodplain management
requirements and that all necessary federal, state, and local permits have been or will be obtained.
The most commonly required federal permits are wetlands permits under Section 404 of the Clean
Water Act of 1972 and incidental take permits under Section 10 of the Endangered Species Act
of 1972. If the floodway revision is approved by FEMA, you will be required to adopt the revised
floodway as part of your floodplain management ordinance and use the revised floodway to
regulate future development.
The procedure for applying for a floodway revision requires a hydraulic analysis similar to that
required to demonstrate that a development would cause no-rise in the elevation of the base
flood. The main difference is that instead of evaluating the impacts of a development in the
floodway on the base flood elevation, the hydraulic analysis is instead demonstrating that the
proposed revised floodway including any modifications that have been made to the channel and
overbank areas within the revised floodway will carry the base flood without increasing the water
surface elevation of that flood more than one foot at any point in the community. This is the same
standard used to designate the floodway that is being revised.
13.2 Development Proposals that Exceed the One Foot Standard
There are limited situations where it may be necessary to allow development in the floodway or
the floodplain that would result in increases in the base flood elevation greater than that generally
allowed by NFIP minimum criteria. This could include:
A proposal for development in the floodway that would cause an increase in the base flood
elevation.
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A request for a revision to floodway boundaries that would result in a floodway that would
result in greater than the allowable one foot surcharge.
A proposal for development in a floodplain where no floodway has been designated that
would cause greater than a one foot increase in flood stage.
Generally, this type of development is discouraged. Designation of the floodway can already
cause up to a one foot increase in flood stage and even this one foot increase can substantially
increase upstream flood damages.
There are situations where it may be in the public interest to allow this development if no existing
buildings are impacted and future buildings are elevated or floodproofed to the new base flood
elevations. The procedure for obtaining a FIRM and floodway revision to allow this type of
development has been established at 44 CFR 65.12 of NFIP regulations. Section 65.12 was
developed to provide a mechanism to address several situations where it was thought to be in
the public interest to allow development in the floodplain that would otherwise violate the
provisions of the community’s floodplain management ordinance. These situations include:
Construction or increase in height of a dam or other water control structure particularly
when it would reduce overall flood damages. Without the procedure at Section 65.12 this
type of development would not be permitted under the community’s floodplain
management ordinance.
Construction or replacement of roads or bridges that cross the floodplain. In situations
where no existing development is impacted by the increase in flood stage there may be
considerable cost savings in building a bridge with a smaller waterway opening.
Other developments that have a net public benefit where there are no practicable
alternative actions that would comply with the community’s floodplain management
requirements.
The procedure can only be used in situations where no existing structures will be impacted by the
increase in the base flood elevation and only if all affected property owners are notified of the
proposed revision. If FEMA approves the revised floodway, the community must adopt the
revised floodway and higher base flood elevations and use them to regulate all future
development. Often agencies proposing to construct such facilities are willing to purchase and
relocate impacted buildings and purchase flowage easements to mitigate the impacts of the
increased base flood elevations.
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44 CFR 60.3(c)(13): Notwithstanding any other provisions
of Sec. 60.3, a community may approve certain
development in Zones A1-30, AE, and AH, on the
community’s FIRM which increase the water surface
elevation of the base flood by more than one foot, provided
that the community applies for a conditional FIRM revision,
fulfills the requirements for such a revision as established
under the provisions of Sec. 65.12, and receives the
approval of the Administrator.
44 CFR 60.3(d)(4): Notwithstanding any other provisions
of Sec. 60.3, a community may permit encroachments
within the adopted regulatory floodway that would increase
in base flood elevations, provided that the community
applies for a conditional FIRM and floodway revision, fulfills
the requirements for such a revision as established under
the provisions of Sec. 65.12, and receives the approval of
the Administrator.
Guidance for meeting the requirements of Section 65.12 can be found in the MT-2 Forms and
Instructions and in Appendix C. A community may allow this type of development only if applies
for and obtains a conditional FIRM and floodway revision and meets specific requirements in
Section 65.12. A FIRM revision will be required to reflect any increase in base flood elevations
due to the development. A floodway revision is required if there is a change in floodway
boundaries. Once the community obtains approval of the FIRM and floodway revision, it must
adopt the higher base flood elevations and revised floodway prior to permitting the development.
13.3 Meeting the Requirements of 44 CFR 65.12
Prior to permitting a proposed development in the floodway that would cause an increase in the
base flood elevation, a request for a revision to floodway boundaries that would result in greater
than the allowable one foot surcharge, or proposed development in a floodplain where no
floodway has been designated that would cause greater than a one foot increase in flood stage
the community must apply for and obtain approval from FEMA of a conditional FIRM and floodway
revision.
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44 CFR 65.12 Revision of flood insurance rate maps to
reflect base flood elevations caused by proposed
encroachments.
(a) When a community proposes to permit encroachments
on the floodplain when a regulatory floodway has not been
adopted or to permit encroachments upon an adopted
regulatory floodway which will cause base flood elevations
increases in excess of that permitted under paragraphs
(c)(10) or (d)(3) of s.60.3 of this subchapter, the community
shall apply to the Administrator for conditional approval of
such action prior to permitting the encroachments to occur
and shall submit the following as part of the application:
The requirements for obtaining conditional approval are found in 44 CFR 65.12. The community
must:
Evaluate alternatives to the development that would meet the requirements of 60.3(c)(10)
or (d)(3) and demonstrate that these alternatives are not feasible.
Provide individual notice to each property owner explaining the impact of the proposed
action on their property.
Obtain concurrence of the Chief Executive Officer of any other community impacted by
the proposed action.
Certify that no structures would be impacted by the increased base flood elevations.
Once the conditional map change has been approved by FEMA the community must adopt the
increased base flood elevations and revised floodway prior to permitting the proposed action. The
increased base flood elevations and revised floodway become part of the ordinance and apply to
all future development in the community.
You are under no obligation to request a floodway revision under 44 CFR 65.12 just because a
developer wants one. It is your floodway that you have adopted in accordance with your due
process requirements and you as a community must approve the proposal and submit it to FEMA.
Remember you will be required to evaluate alternatives to the development that would meet the
requirements of your floodplain management and demonstrate that these alternatives are not
feasible before a CLOMR will be issued by FEMA. In most situations there will be alternatives
that do not require encroachments into your floodway or floodplain that would exceed those
permitted in your floodplain management ordinance.
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14.0 Alterations and Relocations of Watercourses
Communities that participate in the NFIP are also required to assure that flood carrying capacity
of an altered or relocated watercourse in a floodplain is maintained. This requirement applies in
Zone A where FEMA has not provided base flood elevations as well as in Zones AE, A1-30, AO
and AH which have been studied in detail. In order to meet this requirement, communities must
assure that:
Any altered or relocated watercourse has the same or greater flood carrying capacity as
it did before the alteration occurred, and
Once the watercourse has been altered or relocated, the community has an affirmative
responsibility to assure that it is properly maintained.
The community is also responsible for notifying adjacent communities and the state coordinating
office prior to altering or relocating a watercourse and providing FEMA with a copy of this
notification.
44 CFR 60.3(b):
(6) Notify, in riverine situations, adjacent communities and
the State Coordinating Office prior to any alteration or
relocation of a watercourse, and submit copies of such
notifications to the Administrator;
(7) Assure that the flood carrying capacity within the altered
or relocated portion of any watercourse is maintained;
14.1 Definition of Watercourse
Watercourse is not defined in NFIP regulations, but generally means the channel of a river, stream
or drainage way and not the adjacent overbank areas. Placement of fill in the overbank areas
only and outside of the channel is not an alteration or relocation of a watercourse. The overbank
areas are addressed under the NFIP floodway requirements. Watercourses include not only
rivers or streams that are the source of flooding used to determine the base flood and the
floodplain boundaries, but also smaller streams, drainage ways and ditches within the floodplain
that could flood during smaller more frequent events.
14.2 Application
The requirement to maintain the carrying capacity of altered or relocated watercourses applies to
watercourses in all mapped floodplains. In a Zone A where no base flood elevations have been
provided by FEMA, the requirements are particularly important because there are no floodways
designated and no other requirements that would preserve the capacity of the floodplain to convey
floodwaters. Preserving the capacity of the watercourse to convey floodwaters will help prevent
flooding from becoming worse as the area develops. Historically, the failure to maintain the
carrying capacity of altered relocated channels has created numerous flood problems. For
example, it was common practice to force a natural stream into a pipe or culvert when developing
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an industrial area or a subdivision. Frequently these pipes or culverts did not have the capacity
to pass the 1% chance flood or even much more frequent floods. The result was chronic flooding,
repetitive flood losses, and eventually costly corrective measures.
Once FEMA provides a community with base flood elevations and a floodway is designated the
requirements continue to apply to the channel of the river or stream. The floodway designation
will prevent encroachments in the floodplain that cause more than a one foot increase in flood
stage while the (b)(6) and (b)(7) requirements will protect the capacity of the channel of river or
stream to convey floodwaters. The (b)(6) and (b)(7) requirements also will continue to apply to
watercourses such as smaller tributary streams and drainage ways within the floodplain even
though they are not the flooding source that produces the base flood elevation.
Communities are not required to maintain natural streams or channels and watercourses that
were altered or relocated before the community joined the NFIP. Natural streams and
watercourses that were altered or relocated before the community joined the NFIP are treated as
existing conditions that are taken into account when the floodplain is mapped by FEMA. FEMA
recognizes that maintaining natural streams can be costly to the community and often raises
environmental issues. Watercourses that were altered or relocated prior to the community’s
participation in the NFIP can also be costly to maintain and the community may not have the legal
authority to undertake or require their maintenance. However, if these watercourses do silt in or
become clogged with debris or other obstructions, FEMA will eventually have to re-map these
areas to reflect the increased flood hazard. The floodplain will likely become larger and the base
flood elevation will increase. It is usually in the best interests of communities to maintain these
pre-existing altered or relocated channels even though it is not required by FEMA to ensure that
flooding does not increase and to avoid the need for this remapping.
14.3 Maintaining the Carrying Capacity of the Watercourse
Communities must assure that the carrying capacity of the altered or relocate watercourse is
maintained. This means that the carrying capacity of the altered or relocated channel must be
the same or greater than the original watercourse. The community will have to undertake some
kind of analysis to assure that this occurs.
In undeveloped areas designated as Zone A where FEMA has not conducted a detailed
engineering study and not developed base flood elevations, this analysis can be as simple as the
community engineer reviewing the proposal and determining that:
The channel size and cross section are as big, and the channel is as straight as the original
watercourse and that there are smooth hydraulic transitions into and out of the altered or
relocated portion of the watercourse.
The channel sides and bottom are of the same or similar materials to the original
watercourse and that the roughness coefficient is roughly the same.
If there are substantial differences between the altered and relocated channel and the original
watercourse it may be necessary to require that the permit applicant submit a hydraulic analysis
by a registered professional engineer.
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