FEMA defines a floodplain as any area with a 1 percent or greater chance of receiving flood damage over any given year. Though FEMA does not directly regulate building requirements in floodplains, they do offer federally backed flood insurance to communities within a floodplain. In order to qualify for the insurance, however, the community must adopt and enforce certain floodplain management regulations. These regulations must meet the minimum requirements of the National Flood Insurance Program, which uses the International Existing Building Code (IEBC) to set provisions for minimum flood-resistant design and construction.
Developing in Floodplains
The IEBC code forbids developing or disturbing land in floodways unless it has been clearly shown through accepted engineering practices that the new land development will not cause an increase in the level of the base flood.
High-Velocity Wave Areas
In areas where the flood hazard region is subject to high-velocity wave action, all new buildings and buildings seeking substantial renovation are prohibited from using dirt fill for structural support. The buildings also must be beyond the mean reach of high tide.
Detached structures, such as sheds, barns, and garages, must be anchored to a foundation so that they are resistant to flotation and lateral movement caused by flowing water during flood conditions. Fully enclosed structures must have flood openings to allow water to flow in and out of the structure.
Manufactured homes must be built so their ground level is above the design flood elevation, which, if not differently specified by the flood hazard map, is equal to 2 feet. They must also be placed on a permanent, reinforced foundation and must be anchored to the foundation so that they prevent flotation or lateral movement during flood conditions.
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