宝天高速公路西段大(暴)雨引发泥石流危险程度评价

Assessment of the Risk of Debris Flow Triggered by Heavy(Torrential)Rain along the West Section of Baoji-Tianshui Expressway

大（暴）雨可能引发的泥石流等地质灾害,是宝天高速公路西段安全运行的最大威胁.根据宝天高速公路西段1965-2008年麦积国家基本气象站、街子气象哨降水资料及1980-2008年天水农业气象试验站历年土壤水分含量观测资料,分析了宝天高速公路沿线降水、大（暴）雨及土壤含水量分布规律,建立了大（暴）雨引发泥石流可能发生的危险性的评价模式.结果表明：天宝高速公路西段是地质灾害高危险区,也是天水市地区的大（暴）雨中心.自20世纪60年代以来,宝天高速公路段的年降水呈20 a周期变化,大（暴）雨出现次数与年降水量距平百分率呈正相关.大（暴）雨的出现具有明显的季节性,在大（暴）雨出现的4-10月,100 cm土层土壤最大水分容纳量为86-172 mm,40 cm土层为41-69 mm.大（暴）雨引发泥石流的危险性7月最高,4月最低.7-10月泥石流发生的危险程度高于4-6月,主汛期是该线路段泥石流等地质灾害的重点防御时段.

The debris flow and other geologic hazards triggered by heavy（torrential） rain is a remarkable natural disaster along the west section of Baoji-Tianshui Expressway.Based on the precipitation data at Maiji Weather Station and Jiezi Meteorological Post from 1965 to 2008,and data of soil water content at Tianshui Agrometeorological Experiment Station from 1980 to 2008,the distribution characteristics of annual precipitation,heavy（torrential） rain and soil water content were analyzed and a model for evaluating the risk of debris flow triggered by heavy（torrential）rain was established.The result shows that the west section of Baoji-Tianshui Expressway is the area of high risk of geological disaster and the centre of heavy（torrential）rain in Tianshui Municipality.The annual precipitation has varied with a period of 20 years since the 1960s,and the occurrence number of heavy to torrential rain has positive correlation with departure of annual precipitation.Heavy（torrential） rain is a small possibility event and it occurs primarily from April to October.The potential soil water intake capacity within 0 to 100 cm and 0 to 40 cm depth is 86 mm to 172 mm and 41 mm to 69 mm,respectively,from April to October.The risk index of debris flow triggered by heavy to torrential rain has the maximum in July and the minimum in April.The risk degree of debris flow occurrence during July to October is greater than that during April to June,thus more attention should be paid to control the debris flow hazard during the main flood season.To improve the forecast of heavy（torrential） rain and to control the geological disaster comprehensively are the effective measures to ensure the west section of Baoji-Tianshui Expressway safety.