Abstract: To address the defense weaknesses exposed by recent flash flood disasters,the overall architecture and operational workflow of the “Four Pres” platform (Forecast,Early Warning,Rehearsal,and Plan) for flash flood disasters were proposed.Supported by key technologies such as rainfall inversion and fusion,flash flood simulation,multi-stage progressive early warnings,and disaster-prevention knowledge graphs,the platform enabled digital simulation,precise early warning,and intelligent prevention and control.Taking the typical flash flood disaster events in the two small Liyu and Shangqing watersheds in Yunnan Province as case studies,the simulation results for the two flash flood events aligned with the actual flood survey findings.The multi-stage progressive early warning technology provided advance risk alerts while reducing missed and false alarms.The rehearsal assumed worst-case scenarios,with the affected populations in two small watersheds increasing by 22% and 21%,respectively,compared to conventional scenarios.This function enabled risk assessments precise to individual households and persons,providing a basis for the expanded evacuation.Based on the results of early warnings and rehearsals,the proposed defense plans were more targeted and actionable.These findings provide a demonstrative technical pathway for promoting the “Four Pres” capacity construction for flash flood disasters in small watersheds nationwide and enhance flash flood disaster defense capacity.