Abstract
Degradation of exposed bedrock takes place in many rivers worldwide, posing problems of current high interest for river management. Erosion in bedrock rivers is often caused by abrasion from moving sand particles, which is directly linked to the distribution of the alternating zones of exposed bed rock and bed covered with sediment. Erosion by abrasion is active only in a portion moderately covered with sediment. Where there is no sediment and bedrock is completely exposed, no abrasion takes place. And where the bed is fully covered with sediment, no abrasion takes place as well because of the cover effect of the sand.
In the present work, we study experimentally the occurrence of bed degradation in an annular covered flume flow with a simulated bedrock. In curving bedrock channels, due to secondary flow, sand accumulates in the inner bank while the bed is exposed in the outer bank. In the experiment, patterns of topo- graphic changes along the bed could be observed. We correlate the experimental results with expected flow patterns and erosion processes.
