Slope erosion induced by surges of debris flow: insights from field test

The images and videos show the sediment transportation and debris flow erosion along a natural gully Jiangjia Ravine in Southwest China. These types of slope erosion by debris flows has been widely observed in the steep mountainous regions, while the mechanisms of debris erosion, flow dynamics and sediment transport are still not well understood.

In this region, the heavily jointed, weathered lithological setting and sparsely vegetated condition of mountains lead to continuous and intense debris supplies. Debris flow propagates in the channel as a series of surges, with periodical changes of flow flux, velocity and viscosity as controlled mainly by the erodible sediment and water supplies from the upstream. For each individual debris flow surge, the flow front scours the bed, while the tail reworks the bed by debris deposition. The angular rock fragment entrained in the debris flow can effectively increase the erosion intensity.