Summary

Description

For this revision, STARR conducted over 38 miles of revised Coastal Hazard Analysis that included computing wave runup. STARR utilized 79 transects in this study. No new detailed riverine studies were conducted as part of this countywide FIS. For riverine areas, floodplain boundaries were remapped as part of the countywide update to reflect more recent or more detailed topographic and base map data for the county. The floodplain mapping updates consisted of a mixture of redelineation and rectification (refinement) of existing flood boundaries based on the best topographic data and aerial photography available at the time of the study. Redelineation was limited to areas were new, quality topographic data was available and Base Flood Elevations were previously defined. Redelineation was completed on the detailed study areas of the Naselle River, Salmon Creek and South Fork Naselle River. The detailed study reaches along Ward, Wilson and Whitcomb Creeks near the City of Raymond and the Willapa River near Lebam are not covered by new topographic data and was converted to digital format by digitizing the effective FIRMs and refined by making small adjustments to fit the floodplains to new aerial photography. Approximately 4.3 stream miles, including portions of Naselle River and Salmon Creek were studied with base level methods (Zone A). The boundary of the 1-percent-annualchance flood for the South Fork Naselle River near its confluence with Cement Creek was refined by making adjustments to fit the floodplains to new aerial photography and the new topographic data. Those approximate method reaches not covered by new topographic data were converted to digital format by digitizing the effective FIRMs and refined by making small adjustments to fit the floodplains to new aerial photography to ensure that they overlay the water course they represent. These areas include portions of Salmon Creek and Willapa River.