Abstract: In terms of continuity equation, movement equation of transient flow and water head loss theory in open channel in hydrodynamics, the decay process of landslide surge is divided into two stages, respectively, sharp-decay stage and slow-decay stage. And it is assumed that the sharp-decay stage is a kind of exponential decay and the slow-decay stage is a kind of water head loss with propagation distance in open channel. According to both decay rules, the propagation height and climb height of landslide surge along bank are evaluated on basis of initial surge height. Taking Xintan landslide for example, the propagation height and climb height of landslide surge are evaluated. It is concluded that landslide surge increases quickly decays first and then slowly decays; and when the propagation distance is 3 km. the surge height accounts for only 30% of the initial surge height, and accounts for 13% with the propagation distance of 10 km.

Key words: landslide, surge, sharp-decay, slow-decay, propagation