Influences of river boundary conditions on planar channel deformation in the middle and lower reaches of Changjiang River are describeds and research achievements on classification of antiscourability of river bank are introduced in this paper. Two bank failure characteristics of riverbank with double layer texture structure are analyzed, namely, the cross section configuration near river bank for the bank failure reach is close related to river bed scouring due to flow concentration in bank area, and the intermittence during the bank failure process from quantitative change to qualitative change is discovered by the analysis on erosion.resisting capacity of cohesive clay layer soil.