Abstract: In mountainous areas with complex terrain, flash floods triggered by heavy rainfall often carry large amounts of sediment. The process of sediment transport significantly changes the characteristics of flood routing. Traditional flash flood warning systems primarily based on rainfall-runoff-water level relationships fail to adequately consider sediment factors, resulting in limited warning timeliness that cannot meet the practical demands of disaster prevention in mountainous regions. Taking the July 20, 2024 flash flood disaster in Malie Township, Hanyuan County, Sichuan Province as a typical case, a sediment transport module coupled with Modular Distributed Hydrological Model (MDHM) was used to simulate the evolution process of flash floods under measured rainfall conditions and conduct timely warning analysis. Based on on-site investigation and simulation results, a zoning warning method for mountain flood disasters, mountain flood water and sand disasters, and mountain flood debris flow disasters considering sediment deposition effects and steep water level rise rates has been established. Through comparative analysis of traditional flash flood warning versus zonation-based warning considering sediment effects, results indicate that considering the influence of sediment on zoning warning indicators can significantly improve the accuracy and timeliness of flash flood disaster warning, providing technical support and decision-making basis for flash flood disaster prevention in sediment-rich mountainous watersheds.