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<br /> <br />2021 Multijurisdictional Local Hazard Mitigation Plan <br /> <br /> Zone VE, as described above <br /> Zone AE, where flood elevation includes wave heights less than 3 feet. <br />Post-storm field visits and laboratory tests throughout coastal areas of the United States have consistently confirmed <br />that wave heights as low as 1.5 feet can cause significant damage to structures built without consideration of coastal <br />hazards. DFIRMs recently published also include a line showing the limit of moderate wave action (LiMWA), the <br />inland limit of the area expected to receive 1.5-foot or greater breaking waves during the 1-percent annual-chance flood <br />event beyond the coastal VE zones and into the AE zone (Figure 11-1). <br /> <br />Source: FEMA 2014c <br /> <br /> Figure 11-1. Limit of Moderate Wave Action <br /> <br />Addition of LiMWA area to DFIRMs allows communities and individuals to better understand flood risks to their <br />properties. The LiMWA area alerts property owners on the coastal side of the line that being within Zone AE, <br />their properties may be affected by 1.5-foot or higher breaking waves, and may therefore be at significant risk <br />during a 1-percent-annual-chance flood event. While not formally defined in NFIP regulations or mapped as a <br />flood zone, the area between Zone VE and the LiMWA is called the Coastal A Zone. This area is subject to flood <br />hazards associated with floating debris and high-velocity flow that can erode and scour building foundations and, <br />in extreme cases, cause foundation failure (Federal Emergency Management Agency, 2014). <br /> <br />The current effective DFIRM for the County of San Mateo does not delineate LiMWA areas. Future map updates <br />will include this information and should be used to develop additional coastal flooding mitigation items. <br /> <br />11.1.3 Floodplains <br />A floodplain is the area adjacent to a river, creek, lake or the ocean that becomes inundated during a flood. <br />Riverine floodplains may be broad, as when a river crosses an extensive flat landscape, or narrow, as when a river <br />is confined in a canyon. <br /> <br /> <br /> <br /> <br />11-4