It is suggested that rockslide – rock avalanche dams are more complex than is recognized in existing landslide dam classifications. A classification system is proposed emphasizing the three-dimensional relations of the landslide deposit to valley morphology. This system combines a three-step classification taking account of: (A) the plan view distribution of the deposit in relation to valley morphology and the impounded water bodies, (B) the cross valley profile of the landslide deposit as it relates to the buried valley morphology, and (C) the profile of the rockslide debris and the underlying substrate along the thalweg of the valley. It is argued this serves to better describe the dams with respect to the hazard of outburst floods, impoundment histories and the subsequent morphological evolution of mountain stream valleys.