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<br /> <br />f <br />.j <br /> <br />that any map product, hardcopy or digital, is rapidly outdated by new road <br />construction, development and other changes to the surface of the earth. Thus, <br />in use of these data with DFIRHs, users should assess the accuracy of base map <br />sources to be used with DFIRMs with respect to the requirements of the <br />application. <br /> <br />Increasingly, highly detailed large scale digital mapping is becoming available. <br />Such data may be available from State and/or local go'vernments, or from private <br /> <br />.::0<,;;... _'-'. ........ .,,~. <br /> <br />:.:--.::z....:..:;, "";>'1 tOl:..;;o..... :""'e ....::::>0;...;. ..:..... ...:Uii.:.....il............u.. ............ .....<...."""'- '-'___" <br /> <br />j <br />j <br />I <br />I <br />I <br />I <br /> <br />should keep in mind that even though the OFIRM map may be enlarged to overlay <br />these data, the accuracy of OFIRHs is not improved by such enlargement. As <br />digital maps are enlarged users may note that, the appearance of curvil~near <br />features of OFIRMs becoming angular, inconsistencies with large scale topographic: <br />data exist, and similar issues. <br /> <br />Re9ard)e~s of the base map source and scale of digital da~a used in conjunction <br />with DFIRMs, users should bear in mind that the OFI~, is foremost the result of <br />hydrologic and hydraulic engineering process,-;, not. a c~.ttographic process~ <br />Inherent in these engineering processes are mal f unce'rtaint ie~ of both data and <br />methodology. The resulting regulatory Base Flood E:levat~ons (BFEs) and the <br />Special Flood Hazard Area (SFHA) delineations are also impacted by tolerances and <br />specifications used in the development of hardcopy FIl~ maps. Recognizing these <br />issues, FEMA has consistently noted that the FIRM should be used as guide to the <br />spatial extent of flood hazards within a community. Sound judgement must be <br />used, particularly when analyses performed involve arE!aS located within tens-of- <br />feet of SFHA boundary areas. FEMA guidance has been that in such circumstances <br />comparison of the topographic data relative to the sit:e or structure, and to the <br />BFE as determined from the flood profile in the FIS study text, is the best means <br />to resolve issues related to floodplain location for floodplain management and <br />insurance purposes.' <br /> <br /> <br />The conversion of FIRMs to a digital format is expec1:ed to have many benefits. <br />However, users must bear in mind that the simple conve]~sion of FIRMs to a digital <br />format does not inherently improve the engineering qua,lity of the product. Many <br />of the same difficulties with interpretation of flood risk data, and the <br />requirement for users to apply sound judgement in methods selected for decision <br />making and map interpretation remains unchanged. <br /> <br />The "Good Faith Standard" <br /> <br />The mandatory flood insurance purchase requirements e.f the 1973 Act apply only <br />when a structure is located in a SFHA in a community that is participating in the <br />NFIP. Such a structure must be insurable under the rules of the NFIP. Even <br />though a portion of the land parcel upon which the structure is planned may be <br />within a SFHA, the mandatory purchase requirement is only triggered if the <br />structure itself is within a SFHA. <br /> <br />The compliance of lenders with the mandatory flood insurance purchase require- <br />ments of the 1973 Act is based on a the "good faith standard." Determining <br />whether a structure is located in an area of special flood hazard requires the <br />examination of the location of the structure in relCltionship to the areas of <br />special flood hazard as shown on the applicable FIRM. The good faith standard <br /> <br />10/93 <br /> <br />iv <br /> <br />