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<br />Guidelines and Specifications for Flood Hazard Mapping Partners [April 2003] <br /> <br />Availability of Data from Major Storm Events <br /> <br />Surveys of high-water marks taken from the outsides of structures can provide data on wave <br />heights for comparison to the elevations shown in the FIS report and on the FIRM. Additionally, <br />surveys of flood inundation limits in the storm impact area, which can be determined by water <br />marks on structures and debris lines, can be compared to the flood insurance risk zones on the <br />FIRM. An indicator of flood data update needs is when a relatively minor storm event causes <br />flooding and damage well outside the identified flood insurance risk zone on the effective FIRM <br />or well above the BFEs indicated on the effective FIRM. <br /> <br />Significant Beach or Dune Erosion <br /> <br />After erosion has occurred, new survey and mapping of the beaches and dunes may indicate a <br />significant lowering of the dune crest elevations, which would result in a greater landward <br />extension of the hazard area than that is shown on the effective FIRM. <br /> <br />Updated Topographic Data <br /> <br />Many of the coastal high hazard areas were mapped based on wave height studies that relied on <br />USGS 7.5-minute series topographic quadrangle maps, typically with 5-foot contours. If more <br />detailed and/or updated topographic information is available for the community, the better data <br />may provIde a retmed assessment of the wave elevatIOns, hazard zones, and the prImary frontal <br />dune location. <br /> <br />Presence of Areas Not Studied or Studied by Approximate Methods [February <br />2002] <br /> <br />Not all floodprone areas in a community may have been studied using detailed methods as part <br />of the effective flood analyses. Areas that were rural and had little development at the time the <br />analyses were conducted may not have been studied or may have been studied using approximate <br />methods and designated Zone A. <br /> <br />If development has occurred in such areas, detailed-study analyses may be warranted to <br />determine the flood elevations and floodplain boundaries more precisely. The Mapping Partner <br />performing the Mapping Needs Assessment shall evaluate the amount of development near all <br />floodi~g sources in the community that were not studied or were studied using approximate <br />methods. <br /> <br />1.2.3.2 Map Maintenance Update Needs <br /> <br />[February 2002] <br /> <br />Map maintenance needs relate primarily to the "non-engineering" reference information found <br />on the community base map. The base map, which covers the entire geographical area of the <br />community, depicts certain features and their names (e.g., roads, railroads, streams, bench <br />marks) as well as corporate limits and section lines. <br /> <br />The community base map is the preferred source for the features depicted on the FIRM. These <br />features help map users locate properties relative to the flood insurance risk zones; thus, it is <br />crucial that the features be placed and identified accurately. <br /> <br />1-22 <br /> <br />Section 1.2 <br />