Study on the early warning and forecasting of flash floods in small watersheds based on the rainfall pattern of risk probability combination

Flash floods cause great harm to people’s lives and property safety. Rainfall is one of the main causes flash in small watersheds. The uncertainty rainfall events results inconsistency between traditional single pattern actual process, which poses a challenge for early warning forecasting floods. To carry out effective flood forecasting, this paper proposes novel by coupling total peak intensity based on copula functions, i.e., risk probability combination (RPRPC). On basis, Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) hydrological model used simulate rainfall-runoff trial algorithm calculate critical (CR), optimistic-general-pessimistic (O–G-P) mode considering decision maker's preference proposed. watershed Xinxian Henan province, China, taken as case study calculation. show that RPRPC feasible closer process than pattern, Frank function best determining joint distribution intensity, HEC-HMS can be applied watersheds hilly areas. Additionally, both antecedent soil moisture condition (ASMC) have influence CR, variation will change ASMC CR. Finally, effectiveness O–G-P verified.