Abstract:The historical earthquakes in Chuanjiang catchment were one of main dynamic factors which affect the local sediment yield and fluvial processes. The Wenchuan earthquake is the largest earthquake in the recorded history of the Longmenshan fault. Through historical data collection, field study and theoretical analysis, the effects of various natural factors and human activities on the fluvial processes of the piedmont rivers in Longmen Mountains are explored, and the evolution rules of piedmont rivers damaged by strong earthquakes are revealed, and the piedmont river evolution model and its prediction under the changing environment are proposed. The results show that:after the earthquake, different levels of evolutions of piedmont rivers have taken place in the Longmen Mountains, especially in the Shiting River, with the maximum downcutting depth of 27.0 m at the 105 Provincial Highway after the flood season of 2015; there are many factors affecting the dramatic evolution of piedmont rivers in Longmen Mountains after the earthquake and those factors are mixed and interacted with each other. While "water and sediment supply mutation and dissonance slope" are the main internal causes, "engineering barriers and disorder sand mining" are the main external causes. The piedmont river evolution model and its prediction established by the "hydraulic geometry based on the river critical initiation hypothesis" have good applicability and can be used as reference for analyzing the similar strong earthquake-damaged piedmont rivers.