The relocation of a part (about one-half a mile) of the Catawba River near Marion, North Carolina, and the proposed addition of a main bridge and an overflow bridge of U.S. Highway 221 have created the need for a current evaluation of the effects of these physical changes on floodflow in the river. The 100-year flood discharge, elevation-discharge relations, flood profiles, floodway, and flooding effects were determined for 1988 and for proposed bridge conditions.
Analysis of data indicates that for the 100-year flood, the maximum amount of backwater effect from the proposed bridges would be 1.2 feet, and backwater would extend upstream about 6,800 feet. The 100-year flood elevation in the relocated channel reach will be about 6 feet lower than elevations determined in a 1983 U.S. Soil Conservation Service flood study.
Effects of channel relocation and proposed bridge construction on floodflows of the Catawba River near Marion, North Carolina