Abstract. A cusp catastrophe model for alluvial channel regime is established by selecting suitable parameters to reflect channel stability. An equation is obtained from the equilibrium state of channel regime, which is a cusp catastrophe surface in a translated three dimensional coordinate. The stability of channel patterns can be identified by such a model in a direct way, and the 2-D projection of the cusp catastrophe surface can be used to classify alluvial channel patterns. Predictions based on this model are consistent with field observations involving about 100 natural rivers. The results indicate that this method may be applied to study the regime of natural rivers and to assist decision making in river engineering.