The 100-year flood is a recurrence interval, which reflects a frequency analysis of past flood events (over 10 or more years) and corresponds to the 1 in 100 probability of occurrence in any given year (the annual exceedance probability). The elevation of surface water resulting from a flood that has a 1 chance of equaling or exceeding that level in any given year. It is important to note that the use of “100-year flood” can be misleading, since floods of this magnitude can occur more frequently than once every 100 hundred years. For details on the criteria used to map the FIRM flood zones and information on how to read flood maps, see Interpreting Federal Emergency Management Agency Flood Maps and Studies in the Coastal Zone from the Massachusetts Office of Coastal Zone Management (CZM). The BFE is determined by statistical analysis for each local area and is designated on the FIRMs. For flood zones, FIRMs typically indicate a Base Flood Elevation (BFE), which is the elevation the water is expected to reach in a 1% annual chance flood. Base Flood Elevation (BFE) Elevation of the 100-year flood. The V Zones and Coastal A Zones are also referred to as coastal high hazard areas because they are subject to high-velocity wave action from storms. Special flood hazard areas include A Zones (A, AE, AH, and AO Zones) and Velocity Zones (V and VE Zones). Regulatory floodplains are defined by the elevation of the base flood in relation to the elevation of the ground. 1-percent annual chance water-surface elevation: The height, in relation to the National Geodetic Vertical Datum of 1929 (or other datum, where specified), of the flood having a 1-percent chance of being equaled or exceeded in any given flood year (also known as the 100-year flood or the base flood). ![]() ![]() Areas subject to the 1% annual chance flood are identified on the Federal Emergency Management Agency’s (FEMA) Flood Insurance Rate Maps (FIRMs) and National Flood Hazard Layer available on the FEMA Flood Map Service Center and are referred to as special flood hazard areas. The 1% annual chance flood (also known as the 100-year flood) has a 1 in 100 probability of being equaled or exceeded in any given year.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |