Contraction scour at a bridge over Wolf Creek, Iowa

Contraction scour at the State Highway 14 bridge over Wolf Creek in south-central Iowa was caused by a large flood on September 14 and 15, 1992. The bridge is a 30.5-m, single-span steel structure supported by vertical-wall concrete abutments with wingwalls. Approximately 6 meters of scour resulted from the flood. The peak discharge was estimated by water-surface profile analysis to be 2,200 cubic meters per second. A crude stage hydrograph is depicted by a line of gravel deposits created by water overflowing the downstream face of the highway embankment. The fall of the water surface at the bridge was 3.4 m when water began to flow over the highway.