Impact of flow variability on the morphology of a low‐energy meandering river

Abstract

AbstractFew studies have precisely documented the response of stream channels to short‐term flow variability. This paper examines the impact of sequential flows of various magnitudes on the morphology of a low‐energy river in northeastern Illinois, U.S.A. Between June 1986 and November 1988 channel cross‐sections were surveyed on a semiannual basis at 26 locations along a 7.2 km stretch of the Des Plaines River. During this period an estimated 100‐year flood, several bankfull flows, and an extreme low flow associated with a severe drought occurred. The response of the river channel to each of these events was relatively minor. Mean changes for the reach were generally less than 3 per cent for mean depth and less than 1 per cent for width. Statistical analysis indicates that net changes in width and depth over the entire period were not significantly different from zero. This lack of geomorphic response is attributable to low stream power, low hydrologic variability, fine bed materials, and cohesive banks along this stretch of river. Although dramatic changes in channel morphology did not occur, subtleties in geomorphic response were observed that reflect the temporal ordering of hydrologic events.