To intensively study and predict the lateral evolution of alluvial rivers, the theories of riverbank erosion and stability are used to discuss the patterns and the rates of riverbank collapse-retreat in this paper. Based on the mechanism of the riverbank collapse-retreat, three types of analysis models are proposed, which are the sinking-slipping failure, the sinking-toppling failure and the falling failure. Combined with the lateral erosion of river banks, the longitudinal scour of river bed and the critical condition of bank failure, the formula of bank erosion rates is derived. The hydrological data and soil properties of the Yellow River and the Yangtze River were used to validate the proposed formula. The results show that the estimated retreat distance and erosion rates are in consistent with the actual erosion rates of the Yellow River and the Yangtze River, indicating that the proposed collapse-retreat patterns and the formula of bank erosion rates are reasonable.