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<br />Guidelines and Specifications for Flood Hazard Mapping Partners [April 2003] <br /> <br />Mapping Partners that perform Mapping Needs Ass~~ssments shall evaluate any changes in <br />flooding conditions (e.g., changes to the discharges for a particular stream, changes to a beach <br />profile in a coastal area) since previous analyses in support of FIRM and FIS report were <br />performed. <br /> <br />In performing this evaluation, the Mapping Partner shall complete the following activities: . <br /> <br />. Determining the age of the analyses; <br /> <br />. Comparing flood hazard information from recent flood events to the flood hazard <br />information shown on the effective FIRM; <br /> <br />. Assessing factors that affect hydrologic analyses (e.g., publication of new regional <br />regression equations); <br /> <br />. Assessing factors that affect hydraulic analyses (e.g., new bridges or culverts, changes in <br />stream morphology); <br /> <br />. Assessing factors that affect stillwater analyses for coastal flooding sources; <br /> <br />. Assessing factors that affect wave height analyses for coastal flooding sources; and <br /> <br />. Determining the presence of areas that were not studied previously and/or areas that were <br />studied using approximate methods. <br /> <br />Determinina Aae of Analyses <br /> <br />A critical first step in the Mapping Needs Assessment process is to determine when the most <br />recent riverine and coastal analyses were conducted. This information is generally specified in <br />Section 3.0 of the FIS report. (Refer to Appendix J of these Guidelines for further information <br />regarding FIS reports.) <br /> <br />The dates of the effective FIRM and FrS report panels are generally not reliable indicators of <br />when the riverine and coastal analyses were conducted because not all flooding sources, or all <br />portions of particular flooding sources, are revised when an FIRM and FrS report are revised. In <br />other words, a FIRM panel may be revised based on new analyses of only a single flooding <br />source on that panel, while new analyses were not perDormed for all other flooding sources on <br />that panel. For those lmrevised flooding sources, the new effective date of the FIRM panel has <br />no bearing on the date the underlying analyses were conducted. Similarly, not all components of <br />the analysis of a particular flooding source are necessarily revised. For instance, flood elevations <br />may be revised based on a new hydraulic analysis, even if the underlying hydrologic analysis <br />was not revised. <br /> <br />The methodology of coastal analyses has changed substantially since the 1980s. For instance, <br />wave heights were not properly considered until after a 1977 National Academy of Sciences <br />report discussed them; neither were the effects of erosion on the beach and dune profiles <br />properly considered prior to 1989. Mapping Partners that perform Mapping Needs Assessments <br /> <br />1-15 <br /> <br />Section 1.2 <br />