前期有效降水量是泥石流预报的一个关键因子，但是确定此关键因子的常用方法存在参数取值过于人为主观化的问题。为解决这一问题，提出利用模拟降雨截留、入渗和蒸散发等水文过程的方法确定泥石流预报中的前期有效降雨量，并利用基于流域水土耦合机制的泥石流预报系统预报四川省在2013 年7 月9 日的泥石流灾害来检验该方法。结果表明: 利用水文过程模拟方法确定的前期有效降水更适用于泥石流预报，泥石流预报的漏报率比常用的降雨衰减经验公式低21. 1%，能更好地为泥石流防灾减灾服务。

Antecedent effect rainfall is a key factor in debris flow forecasting, but the current method used to calculate this factor has the defect that the parameters determination of the method is too subjectively. In order to solve this problem, a hydrology-process (e.g. rainfallinterception, rainfall infiltration and evapotranspiration) based method to calculate the antecedent effect rainfall for debris flowforecasting is proposed. Taking the antecedent effect rainfall calculated by the hydrology-process based method and the empiricalbased method as the initial value, the debris flow forecasting system for Sichuan province based on the water-soil coupling mechanism is employed to forecast debris flow disasters induced by the heavy rainfall on July 9, 2013 in Sichuan province. Theforecasting results show that the hydrology-process based method that used to calculate the antecedent effect rainfall is more suitable for debris flow forecasting, because the failure prediction rate of debris flow forecasting is 21.1% lower than the method of the empirical formula of the rainfall attenuation. Consequently, the hydrology-process based method that used to calculate theantecedent effect rainfall can serve the debris flow mitigation better.