Experimental study of effects of riverbed composition on the riverbank erosion process

Abstract

Riverbank erosion is a common natural river process that threatens the security of instream structures, as well as public and private property. In this study, two sets of tests were performed (direct shear tests and flume tests) to study the effects of riverbed soil composition on the stability of riverbanks. The results of the direct shear tests demonstrated that the riverbank material became increasingly cohesive with increasing clay content and decreasing water content. The internal friction angle decreased monotonically with increasing clay content, but increased towards a peak value, before decreasing thereafter, with increasing water content. The results of the flume tests showed that, for each riverbank material, an increase in bed mobility (non-cohesive bed material > cohesive bed material > fixed bed) increased the equilibrium channel width, riverbank erosion volume and bed degradation. In the first 25 min of the test, the temporal channel width was greater when the bed mobility was lower; after 45 min, the temporal channel was wider when the bed mobility was higher. For each bed material, the riverbank erosion volume and temporal channel width were greater with a non-cohesive bank than with a cohesive bank.