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<br />. <br /> <br />Buildings in Hazardous Velocity Areas <br /> <br />In coastal A zones, or in riverine A zones where flood velocities exceed 5 feet per second, fast- e <br />flowing floodwaters can exert considerable pressure on solid foundation walls. This hydrody- <br />namic pressure, as described in the following section, may destroy a building's foundation. In <br />such areas, foundations that allow floodwaters to flow freely beneath the building should be <br />considered. Foundations such as piles, piers, or columns will provide the appropriate level of <br />safety to a building located in a hazardous velocity area, if properly embedded and anchored. <br />See the discussion of hydrodynamic pressure for design guidance. <br /> <br />Buildings in A-zone floodplains with velocity floodwaters may have breakaway walls con- <br />structed in areas below the BFE. Compliant foundation openings are required in breakaway <br />walls in A zones. <br /> <br />Buildings with Attached Garages <br /> <br />Any new or substantially improved residential building constructed in an A zone must have its <br />lowest floor at or above the BFE. Many of these buildings have structurally attached garages <br />with floor slabs below the BFE. Because such a below-BFE attached garage is an enclosed area <br />below the BFE, openings are required either in the exterior walls of the garage or in the garage <br />doors themselves in order to meet the NFlP openings criteria (see Figure 3). Openings are <br />required because they prevent flood damage to the garage and subsequently to the structurally <br />attached residence. Garage doors without openings specifically designed to allow for the free <br />flow of floodwaters do not meet the openings requirement. The human intervention necessary to <br />open garage doors when flooding threatens is not an acceptable means of meeting the openings e <br />requirement. Gaps that may be present between the door segments and between the garage door <br />and the garage door jamb do not guarantee the automatic entry and exit of floodwaters. There- <br />fore, openings are required either in the exterior walls of the enclosed area or in the garage doors <br />themselves. Openings in garage doors must either meet the non-engineered openings require- <br />ments or be certified by a design professional. <br /> <br /> <br />EE ill <br /> <br />Lowest Floor <br /> <br />E8 <br /> <br /> <br />BFE <br />... <br /> <br />Foundation Opening <br />rr ypicall <br /> <br />Enclosed Area <br /> <br />Figure 3. Compliant Residential Building Built on Solid Foundation Walls With Attached Garage <br /> <br />e <br /> <br />4 <br />