Experimental study on the formation and development of alluvial river meanders with non-cohesive sand bedded natural river model

Laboratory experiments on riverbed evolution were carried out with non-cohesive sand.River meanders were created in model test by adjusting the rate of flow and the initial river pattern.The law of widening of alluvial rivers was analyzed and studied with experiments.Additionally the evolution of typical river meanders was also investigated.It was revealed that the lateral stability of channels is vital to river meander growth,and the river in this experiment evolved into branching or braided patterns due to the lack of anti-erodibility of sediment,which leading to bank failure.The pattern of bank retreat is related not only to the anti-erodibility of bank,but also to local hydrodynamics feature and bank slope etc.The channel widening rate declines exponentially with time,reflecting the degree of incompatibility between cross section and flow conditions in river.The time-scale of river cross section evolution is far smaller than that of lateral migration of river channel.Typical river meanders develop laterally in the way of local disturbance causing bank failure.