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Parkview Addition-SY 840727CONDITIONS AND CRITERIA FOR MAP REVISIONS A. Introduction This document describes the conditions and criteria for revising a Flood Insurance Study (FIS) under Part 65 of the National Flood Insuranc~ Program (NFIP) regulations. The Federal Emergency Management Agency (FEMA) recognizes that FISs may require revision due to new information becoming available or through physical changes in flood plains. This document defines the situations that fall under Part 65 of the NFIP regulations and describes the procedures for correcting or updating Flood Insurance Rate Maps (FIRMs) and Flood Boundary and Floodway Maps (FBFMs). B. Definitions A Letter of Map Amendment (LOMA) issued under Part 70 of the NFIP regu- lations indicates whether or not a structure(s) or proposed structure(s) is located in a Special Flood Hazard Area (SFHA) as shown on a FIRM or Flood Hazard Boundary Map (FHBM). A LOMA removes a property from the SFHA and thereby makes inapplicable the Federal requirement for the purchase of flood insurance. For more information regarding LOMAs, refer to "Condi- tions and Criteria for Letters of Map Amendment." A Conditional Letter of Map Revision~ or belief letter, issued under Part 65 of the NFIP regulations is FEMA's comment on the effectiveness or impacts of a proposed flood control project or flood plain modification. It is based on FEMA's review of the proposed project and states that were the proposed project built as designed, it would be cause for a map revision. A Letter of Ma~ Revision (LOMR) can be issued under Part 65 of the NFIP regulations as an expeditious means of revising a FIRM or FBFM. The LOMR gives a detailed description of the Base Flood Elevation (BFE) and graphic changes that will be made to the SFHA currently delineated on the effec- tive FIRM and/or FBFM. LOMRs involving BFE changes are always succeeded by a physical map revision. A physical map revision under Part 65 of the NFIP regulations involves changing and republishing the existing FIRM and/or FBFM to reflect any updated condition, valid LOMAs and LOMRs are incorporated into map revisions. C. Reasons for Revision FEMA will revise an effective FIS to reflect new information which shows the original FIS to be incorrect and to reflect physical changes which invalidates the original FIS analyses or presentation of data. Updated or corrected topographic mapping, hydrologic data, or hydraulic data F IA/ORA/RSD 7/2 7/84 constitute new information which may warrant a revision. Flood protection projects and any form of topographic alterations (cut and fill) constitute physical changes which may also warrant a map revision. D. General Revision Policy within the statutory criteria established for appeals, revision requests will be evaluated based on the possession of knowledge or information indicating that the effective elevations are scientifically or technically incorrect. In certain situations where new information shows mathematical or measurement errors in the original FIS, FEMA will accept the respon- sibility for revising the FIS provided the requestor submits the basic data necessary to correct the problem. Where revision requests are based on t_he application of alternative methods, appellants are required to demonstrate that the new analyses result in more correct estimates of base flood elevations, thus demonstrating that FEMA's estimates are incorrect. In these situations, where a revision request is being made based on improved data, methods, or applications, the community (or requestor through the community) must accept responsibility for providing all data and analyses necessary to update the FIS. If a physical change resulting from development warrants a revision to the existing analyses, FEMA will not undertake this new technical analysis. The requestor, through the community, must accept responsibility for providing all data and analysis necessary for updating the FIS. E. Communit~ Ma~ Revision Requests The map revision process cannot be initiated without the community's endorsement since it is the community that adopts the effective FIS. Therefore, any individuals requesting, a change to the FIS, must do so through the community. The community, in turn, may support the request and forward the information to FEMA for evaluation. FEMA will review the request to ascertain that the following conditions are met before eval- uating t_he revision request. Condition The community must endorse the revision request and demonstrate prepared- ness to accept responsibility for the operation and/or maintenance of any structural measures (e.g. channel improvements or levees) involved. The request submittal should include the following: I .1 A statement that the community endorses the revision request. If the basis for the revision request is a channel modification, the completion of a dam, levee, or any other structural measure, evidence is required to demonstrate the design is adequate and that mainte- nance and operation provisions, where applicable, have been made. The submittal must indicate what entity has operation and maintenance responsibility and how they will be accomplished. If maintenance is to be accomplished by an agent other than the community, a legal 1.3 provision (ordinance) for community monitoring and backup maintenance is required. The submittal must indicate that, where necessary, state approval of the revision has been obtained. Condition N~nnber 2 If the revision request is based on information showing a mathematical or meas%Lrement error in the original analysis, the submittal must include the fo 1 lowing: 2.1 Documentation that identifies the specific source of the error. 2.2 2.3 A written description of the new information and how it differs from the existing FIS information. Basic data supporting the revision request to enable FEMA to revise the FIS. In most cases, this data must be certified by a registered professional engineer or licensed land surveyor. Updated topographic maps, revised community boundary maps including annexation ordi- nances, and channel, dam, or bridge structure plans which illustrate the correct dimensions are examples of the basic data required. Condition Number 3 If the revision request is based on improved application of hydrologic, hydraulic, or other methods, or use of better data in applying such methods, the requestor must submit the following: 3.1 Documentation that identifies the error in the application or in the inferior data in %he original analysis and supports why the appli- cation is incorrect or the data is inferior. 3.2 Engineering analyses applying %he same basic methods utilized by FEMA but with the changes itemized. 3.3 Alternative engineering analyses utilizing the methods or assumptions determined to be correct. 3.4 3.5 Background technical information which supports the requestor's changes as being more correct. Certification by a registered professional engineer or licensed land surveyor of the correctness of any alternate data utilized or mea- surements made. 3.6 Documentation of all locations where the requestor's base flood elevations are different from FEMA's. 3 Ail engineering analyses performed must substantiate that the revised hydrologic or hydraulic analyses meet F~_~MA requirements as well as any state or community requirements. F. General Technical Guidance Flood plain revisions should be based on the hydraulic model used to develop the flood profile and flood boundaries currently in effect. The community should request, through the FEMA Regional Office, a copy of the input data used in the computer model for its effective FIS. Where the input data representing the original hydraulic model is unavailable, or where a t~chnically superior model can be used, an approximation should be developed. A new model should be established using the original cross- section topographic information, where possible, and the discharges contained in the FIS which established the original BFEs. The model must use the same effective flow areas as established in the original analysis and must be calibrated to reproduce the original base flood elevations within 0.1 foot. Any differences between the new analysis and the orig- inal profile must be justified on an engineering basis. After the model has been checked and matches the original base flood elevations, the model can be modified for new flood plain runs. The analysis will be accomplished as specified for the following conditions: Discharge Decreases. Hydr'aulic analyses may be revised when a base flood discharge decreases as a result of structural improvements, such as the construction of a flood control dam or other significant retention facil- ities. Hydraulic analyses should not be revised based on a computed discharge reduction which results from changed methodology or longer stream gage records, unless the change is statistically significant. The statistical significance criteria are discussed in Section 2-6 "Hydrologic Analyses" of FEMA's Guidelines and S~ecifications for Stud~ Contractors (dated September 1982). If it is evident that the change is statistically significant, the original hydraulic model should be rerun, changing only the discharges. In cases where the statistical significance test does not apply, a determination by a state or Federal agency that the change is significan~ may be a¢¢ep=ed as a basis for a map revision. Discharge Increases. If watershed conditions have resulted in a signifi- cant (defined as above) increase in discharge, the original hydraulic model must be run with the increased discharges. Channel Modification. The original hydraulic model will be modified to include the channel modification, and any other encroachment occurring subsequent to the original flood plain delineation. In all situations, the revised hydraulic analysis should be modified to include current conditions as well as any encroachment to the flood plain that may have occurred since the original model was developed. The revised hydraulic analysis should also include a zone determination, and if only a portion of the existing hydraulic analysis is revised, the upstream and downstream portions of the revised analysis should coincide (2) Send a Letter of Map Revision (LOMR) to the community stating that the review of the submitted material has resulted in an official map revision but that a physical map revision is not warranted at this time. The LOMR will give a detailed description of the BFE and graphic changes that have been made to the SFHA currently delineated on the effective FIS. The material, including a copy of the maps showing the revised information, will be filed for incorporation at a later time into a physical map re~ision. The approved map re~ision copies will be dated. Since it is possible that FEMA has responded to a map revision request in this manner, all FIS users are encouraged to contact the community before proceeding with plans for development within the flood plain areas. LOMRs that result in an increase in BFE will also be preceded by a 90-day appeals period. An appeals period for a LOMR which only decreases BFEs will be pr~ided subse- quent to the issuance of the LOMR. (3) Send a letter to the community with a copy to any other requestor stating that the submitted material is not adequate to make an evaluation and offer them the option of submitting additional infor- mation. (4) Send a letter to the community with a copy to any other requestor stating that the submitted material appears to justify a map re- vision, but because not enough information was submitted the com- munity will be placed on a 'list for restudy consideration, as funds permit, unless the community can submit additional information. (5) Send a letter to the community with a copy to any other requestor stating that the submitted material does not substantiate their request for a map revision and that the file will be closed unless the community can submit additional information to substantiate their request. H. Submittal of Material Submit material to the FEMA Regional Office. The Regional Office will review material for completeness, concur with the proposed changes, approve any maintenance ordinances, and forward the necessary material to FEMA Headquarters. FEMA Headquarters will review the hydrologic/hydraulic backup material, engineering design, and any plans of operation and maintenance (where ap- propriate), request additional information as necessary, then respond to the community by means of the appropriate action defined under Section F above. To obtain further information on the conditions and criteria for map revisions, communities are encouraged to contact the appropriate FEMA Regional Office or FEMA Headquarters in Washington, D.C., at (202) 287- 0230, prior to requesting a map revision.