Erosion of collapsed riverbank and interaction with channel

After failure of a riverbank, a cohesive block of soil can temporarily lie at the toe of the bank until it is eroded away. To investigate the erosion of this collapsed block and its interaction with the river channel, a series of experiments was conducted under similar hydraulic conditions within a U-bend flume. The flow structure and channel topography were measured and analysed in detail. The presence of the collapsed block was found to cause a 1·1–1·6 times greater downstream bank retreat, while the counter-rotating circulation cell and smaller near-bank velocity protect the bank against erosion upstream of the block end. The scour percentage of the block head or end was about 1·5–2 times larger compared with that at the middle. Cohesive soil from the block fills the gap of non-cohesive riverbed material in the downstream convex bank and can result in a maximum bed deposition thickness increase of more than 300%. The results also provide a valuable experimental dataset and a theoretical basis for pract...