National Flood Insurance Program (NFIP) Policy Index
Standing water or slowly moving water can induce horizontal hydrostatic forces against a structure, especially when floodwater levels on different sides of a wall are not equal. Also flooding can cause vertical hydrostatic forces, or flotation. Hydrostatic forces are one of the main causes of flood damage.
IS-9 Managing Floodplain Development Through The National Flood Insurance Program (NFIP) (Page 1-27) (PDF 8MB, TXT 1MB) (entire document)