13.07.2015 Views

47.5 MB - The Whole Building Design Guide

47.5 MB - The Whole Building Design Guide

47.5 MB - The Whole Building Design Guide

SHOW MORE
SHOW LESS
  • No tags were found...

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

“Base flood elevation” is the elevationabove a datum to which floodwaters arepredicted to rise during the 1-percentannual-chanceflood (also called the “baseflood” or the 100-year flood).from extreme hurricane storm surges, extreme riverineflooding, dam failures, or overtopping or failure of levees.<strong>The</strong> flood hazard maps prepared by the NFIP show different floodzones to delineate different floodplain characteristics (see Figures2-3 and 2-4). <strong>The</strong> flood zones shown on the NFIP maps, and someother designations, are as described below.A Zones: (also called “unnumbered A Zones” or “approximate AZones”). This designation is used for flood hazard areas whereengineering analyses have not been performed to developdetailed flood elevations. Base flood elevations(BFEs) are not provided. Additionalengineering analyses and site-specific assessmentsusually are required to determine thedesign flood elevation.AE Zones or A1-A30 Zones: (also called “numberedA Zones”). <strong>The</strong>se designations areused for flood hazard areas where engineeringanalyses have produced detailed flood elevations andboundaries for the base flood (1-percent-annual-chance flood).BFEs are provided. For riverine waterways with these zones, FISsinclude longitudinal profiles showing water surface elevations fordifferent frequency flood events.Floodways: <strong>The</strong> floodway includes the waterway channel and adjacentland areas that must be reserved in order to convey thedischarge of the base flood without cumulatively increasing thewater surface elevation above a designated height. Floodwaysare designated for most waterways that have AE Zones or numberedA Zones. FISs include data on floodway widths and meanfloodway velocities.AO and AH Zones: <strong>The</strong>se zones include areas of shallow floodingand are generally shown where the flood depth averages from 1 to3 feet, where a clearly defined channel does not exist, where thepath of flooding is unpredictable, and where velocity flow may beevident. <strong>The</strong>se zones are characterized by ponding or sheetflow.BFEs may be provided for AH Zones; flood depths may be specifiedin AO Zones.2-12 MAKING CRITICAL FACILITIES SAFE FROM Flooding

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!