In natural systems, banks are usually most active on the outside of a bend or meander. HEC-RAS is a one-dimensional model and does not simulate the multi-dimensional forces that cause this preferential erosion. Banks migrate more on the outside of bends because multi-dimensional effects produce higher shears there. Because HEC-RAS uses an excess shear equation to compute scour, users can simulate preferential bank scour by decreasing the critical shear at bend cross sections. This will approximate the physical process, increasing the (τ-τc) shear difference by decreasing the critical shear instead of increasing the shear.