SPATIOTEMPORAL DYNAMICS OF A CHUTE CUTOFF ON THE EMBARRAS RIVER, ILLINOIS

A meander bend on the Embarras River south of Charleston, IL has developed a chute cutoff across the point bar. Despite being present for decades, the cutoff channel has not captured the flow of the main channel. The cutoff and main channels are now separated by an island that accumulated large woody debris at its head. The purpose of this field study is to examine changes in the morphology, bed-material texture, and flow of the channels over time to gain insight into the spatiotemporal dynamics of cutoff development in a low-energy, low-gradient meandering river. Surveys of bed topography with a total station and bed-material sampling followed a series of flow events during late winter-autumn 2018. Recent flow events have pushed the large woody debris onto the island, revealing a large bar extending upstream from the head of the island. In the main channel, pools associated with meander bend curvature are adjacent to this bar. On the cutoff side of the bar, bed scour and upper bank erosion and failure occur upstream and into the entrance of the cutoff channel. Flow data collected with an acoustic Doppler current profiler will follow a high-discharge event to relate spatial patterns of three-dimensional flow structure and bed morphology.