合理的降雨阈值是确定区域暴雨泥石流减灾防灾的关键.为了探求诱发舟曲地区泥石流的降雨阈值,本研究以舟曲三眼峪、罗家峪为例,研究了在前期含水量一般(湿润)和干旱两种条件下,触发不同预警级别泥石流的降雨雨强与历时函数关系,采用水文学方法计算了不同频率下洪峰流量以及对应的不同规模泥石流启动降雨量阈值.结果表明:在前期含水量干旱和一般条件下,三眼峪、罗家峪泥石流红色I级降雨预警值为56.10 mm/h和50.86 mm/h、橙色Ⅱ级预警值为40.70 mm/h和37.87 mm/h、黄色Ⅲ级预警值为31.74 mm/h和29.88 mm/h、蓝色Ⅳ级预警值为23.83 mm/h和21.69 mm/h,预备Ⅴ级预警值为7.31 mm/h和15.69 mm/h、预备Ⅵ级预警值为10.16 mm/h和9.48 mm/h;不同预警级别条件下的降雨雨强与降雨历时成I=α ×Dβ幂函数关系,和数值在不同预警级别下成规律性变化;能够诱发舟曲地质灾害的降雨特征可分为两种:一是降雨雨强大的单峰型短历时强降雨(“点雨”);二是降雨雨强小、持续时间较长的“绵绵细雨”.研究成果可作为舟曲区域暴雨泥石流监测预警研究提供科学依据.%A justified precipitation threshold would act as a solution to the engineered control of regional storm-type debris flow.In order to estimate the triggering precipitation for debris flows haunting Zhouqu region,Gansu province,China,two recent debris flow events occurred at Sanyanyu gully and Luojiayu gully,were exemplified for determination of the threshold value.Given antecedent soil moistures in either wet (regular) or dry circumstances,it studied correlation between rainfall intensity and duration in the process of motivating debris flow to various forewarning level.Hydrography method was borrowed to calculate the peak discharges at various frequencies and the associated precipitation threshold in initiating debris flow to varied extents.Results showed that as antecedent soil moistures were in the regular and dry conditions,early warning precipitation in the level of red Ⅰ at Sanyanyu gully and Luojiayu gully arrived to 56.10 mm / h and 50.86 mm / h separately;in orange Ⅱ pre-warning level it was 40.70mm / h and 37.87 mm / h;in yellow Ⅲ pre-warning level it was 31.74 mm / h and 29.88 mm / h;in blue Ⅳpre-waming levelit was 23.83 mm / h and 21.69 mm / h;in preparatory pre-warning level it was 7.31 mm / h and 15.69 mm / h;in preparatory Ⅵ pre-warning level was 10.16 mm / h and 9.48 mm / h.Relationship between rainfall intensity and duration at different levels of pre-warning could be interpreted as power function,I =α × Dβ,exhibiting regular changes in value in relation to levels of pre-warning.Rainfall leading to geohazard occurrences in Zhouqu region were characterized as two types:one took place with a short duration in the unimodal shape,concentrated precipitation,like as "Point Rain";another type occurred with low intensity,a longer duration,like as "drizzle".This research will serve as a scientific initiative for regional monitoring and early warning of storm-type debris flows in Zhouqu region and it contributes to geologic hazard prevention and mitigation at local level.
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