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limited clogging to be 10 perc,!!nt of .cu1vert areas and 1 foot on each side of bridge piers. These values may vary from structure to structure depending on field elevation of .structure configuration. Flow breakouts for floods greater than the 10-year discharge on Fountain Creek occur at the U.S. Highway 24 bridge crossing. These breakouts flow through the M4Initou Avenue underpass and rejoin Fountain Creek at cross section C. As a .resu1t, the peak discharges for the 50-, 100-, and SOO-year floods were reduced 700, 2,100, and 9,250 cfs, respective~y. . Inadequate channel capacities 'of Sutherland Creek downstream of cross section A, coupled with the inadequate culvert capacity under the U.S. Highway 24 Access Road, result in breakouts of flow greater than the 10-year flood. Breakout flows occur in both the east and west overbanks. The, lack of any defined flow channels results in a complex flow patt,!!rn which consists of overland flow and flow along U.S. Highway 24. These flows, joined with the breakout flows from Fountain ,Creek, cannot be modeled with a one-dimensional backwater model. Therefore, no elevations have been determined for the downstr~am portion of Sutherland Creek and the flows along U.S. Highway 24'and Manitou Avenue. Therefore, the flood hazard area ~as been anal~zed by approximate methods. . The approximate elevations for the upper portions of Williams Canyon and Beckers Lane Tributary were developed using cross sections taken from a U.S. Geological Survey topographic map enlarged to a scale of 1 :4,800,i with a contour interval of 40 feet (Reference 13) and the COE HECi-2 computer program (Reference 10), which generates a top width forjeach section based on cross section area, drainage area, 100-year discharge, slope, and roughness values. All elevations are referenced, to the National Geodetic Vertical Datum of 1929 (NGVD). Elevation reference marks and descriptions used in this study are shown on ithe maps. 4.0 FLOODPLAIN MANAGEMENT APPLICATIONS The NFIP encourages State and 1pca1 governments to adopt sound floodplain management programs. Therefore, each Flood Insurance Study provides 100-year flood elevations and de1inea~ions of the 100- and 500- year floodplain boundaries and 100-year f100dway to assist communities in developing floodplain management measures. ~ . 4.1 F160dp1ain Boundaries To provide a national standard without regional discrimination, the 1 percent annual chance (lOO-year) flood has been adopted by FEMA as the base flood for floodplain management purposes. The 0.2 percent annual chance (500~ye*r) flood is. employed to indicate additional areas of flood risk, in the community. For each stream studied by detailed methods, the 100- and 500-year floodplain 12