Impacts of the flexible net on riverbed evolution in degrading channels

The short-term dramatic degradation of the riverbed poses a great threat to the river and the functioning of infrastructure in its vicinity. In this paper, a straight flume experiment was carried out to measure the velocity, water level, riverbed elevation, and riverbed morphology under different experiment conditions, combined with the SfM (Structure-from-Motion) method to generate the riverbed DEMs and orthomosaic, and the impact of flexible net on riverbed evolution of degrading channel was studied. This study reveals that under the action of the flexible net, the degradation mode of the riverbed changes from parallel degradation to rotational degradation with erosion datum as the fulcrum, and with an increase in the longitudinal length of the flexible net, the riverbed's protection efficiency grows. The flexible net can effectively limit the movement of sediment under the net, and the finer sediment silting raises erosion datum elevation. It is noticed that the location and morphological characteristics of the downstream scour holes are greatly affected by the deformation of the erosion datum. The scour hole shows an asymmetric distribution because of the uneven scouring of the flow to the downstream riverbed. The research results have a certain guiding role in the management of degrading channels.