Numerical simulation of gravel river widening

A numerical model is described which simulates bank erosion in a straight channel composed of noncohesive sediment. The model predicts the distribution of boundary shear stress, cross-channel sediment transport rates and the evolution of the bed topography. When erosion produces a bank slope which exceeds the angle of repose, widening occurs by a planar bank failure. Equilibrium channels produced by the model have flat beds and curved bank regions which are similar to the classical cosine stable bank profile. Equilibrium values of dimensionless depth are inversely proportional to the slope, as suggested by previous studies. The model also reproduces the exponential cross sections created during laboratory experiments. However, as the computations proceed, the exponential profiles slowly develop a flat bed and a curved bank region, suggesting that past flume experiments of channel widening may have frequently been terminated before a stable equilibrium form had evolved.