Special siting and design restrictions and requirements exist for each of these areas. The most hazardous floodplain areas will generally be close to coastal shorelines (zone V, also called the coastal high hazard area-CHHA), floodways (areas closest to the centerline of major streams and rivers-see illustration below), and alluvial fans. "V" zones are mapped exclusively in coastal floodplains. "A" zones can be mapped in inland or coastal floodplains. "A" zones are those areas within the 100–yr floodplain where high velocity wave action is not expected during the Base Flood."V" zones are those areas within a coastal floodplain where high velocity wave action can occur during the Base Flood.The SFHA is usually divided into flood hazard zones beginning with the letter "A" or "V" (see Flood Hazard Zone Table): Therefore the SFHA is not associated with a flood event that happens once in a hundred years, it is associated with a flood event that has a one percent chance of occurring each and every year. The SFHA is more precisely defined as the floodplain associated with a flood that has a 1–percent annual chance of being equaled or exceeded in any given year. The Base Flood Elevation (BFE) is the water surface elevation associated with the 100–yr flood, and has a one-percent chance of being equaled or exceeded in any year. The Special Flood Hazard Area is the area known as the 100–year floodplain, or the area subject to flooding during the Base Flood. Flood Insurance Study (FIS) reports are produced as part of each flood hazard study and provide data not shown on the FIRMs. Flood Insurance Rate Maps (FIRMs- see Sample below) are the most common of the flood hazard maps. Specifically, the NFIP has produced a series of maps-Flood Insurance Rate Maps (FIRM), Flood Hazard Boundary Maps (FHBM), and Flood Boundary and Floodway Maps (FBFM)-which depict Special Flood Hazard Areas (SFHA) and Base Flood Elevations (BFEs). The NFIP has mapped flood hazards in approximately 20,000 communities within the United States. Definitions and background for common flood hazard and mapping terms used below are available from FEMA. Through its Mitigation Division, FEMA manages the National Flood Insurance Program (NFIP). where floodproofing is permitted, employing appropriate methods and materials to either dry-floodproof or wet-floodproof those portions of the building below the design flood levelĪ number of federal agencies have been involved in identifying flood hazards, but the agency that is most directly involved (also, in the regulation of development within flood hazard areas, and in responding to flood disasters) is the Federal Emergency Management Agency (FEMA).using flood-damage-resistant materials for any portions of the building below the design flood level.designing the building foundation and any portions subject to flooding to withstand design flood conditions and loads, and.elevating as much of the building as possible above the design flood level,.Planning, designing and constructing the building to minimize any potential flood damages by:.In the United States, these practices are based largely on the National Flood Insurance Program (NFIP) and its regulations governing land management and use ( 44 CFR Part 60).ĭetermining design flood characteristics anticipated at the selected site, both now and over the life of the building The likelihood and impacts of these damages can be minimized through the use of siting, design, construction and maintenance practices appropriate to floodplain areas. contamination of the building due to flood-borne substances or mold.degradation of building materials, either during the flood or sometime after the flood, and.direct damage during a flood from inundation, high velocity flow, waves, erosion, sedimentation and/or flood-borne debris,.One or more water bodies can contribute to flooding at a given site-a river, stream, ocean, bay, lake, pond, storm water retention/detention area, etc.-depending on local topography and hydraulic/hydrologic conditions.įlooding can damage buildings and their contents in many ways, but the most common flood damages arise from: FEMA more specifically defines a flood as a general and temporary condition of partial or complete inundation of normally dry land areas from (1) the overflow of inland or tidal waters or (2) the unusual and rapid accumulation or runoff of surface waters from any source. Flooding is the overflow of excess water from a water body onto adjacent lands.
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