中文摘要：

震后泥石流松散物质显著增多,临界雨量降低,导致泥石流暴发频率增加、规模增大,从而使震后灾区泥石流堵江事件频繁发生,给灾区带来严重的二次灾害。为了评价震后泥石流堵江概率大小,本文在野外考察基础上,获得研究区泥石流沟基础数据,并根据水文模型计算不同频率下的泥石流规模;在此基础上利用泥石流堵江公式,获取研究区域泥石流堵江危险程度（数值）,并结合研究区域已发生的泥石流堵江事件,界定了泥石流堵江公式的临界值,使之能够更加准确用来判定泥石流堵江概率,并对5.12地震极震区都汶公路沿线的7条泥石流在不同频率下的泥石流堵江概率进行评价。评价结果显示：牛眠沟和关山沟在暴发50a及其以上泥石流时,会发生堵江;烧房沟、红椿沟和磨子沟在暴发10a及其以上泥石流时,会发生堵江事件;洱沟和太平沟在暴发5a及其以上泥石流时便可能发生堵江;上述泥石流沟一旦发生堵江,便会给映秀镇和都汶公路带来严重灾难。通过本文获取的堵江临界值可以作为判定泥石流堵江的参考标准,为泥石流防治、预报提供参考,同时可以为灾后重建和预防二次灾害提供科学借鉴。

英文摘要：

The total amount of the loose masses due to collapses and landslides by Wenchuan Earthquake reached about 28×108m3.the loose masses can provide abundant materials for debris flows for long term.The critical rainfall has decreased significantly.The debris flow events have occurred at high frequency and in group.Their discharges have increased.Blocking of main rivers by debris flows have occurred more frequently post the earthquake and led serious secondary disasters in the quake-hit areas.In order to evaluate the probability of blocking river by debris flow,the basic data of debris flow gullies are obtained on the basis of field investigation and scale in different precipitation frequency according to a hydrological model.Then based on the above data and the differentiation formula of debris flow blocking river,this paper assesses the degree of debris flow blocking main river of the study area.It then defines the threshold value of the differentiation formula combined with debris flows that have occurred in the study area and blocked rivers.As a result,it can be used to determine the probability of debris blocking river more accurately.Seven debris flow gullies of the study area are evaluated at different precipitation frequencies.The results show that the debris flow of Niumian gully and Guanshan gully can block the Minjing river under the 50 years return period precipitation.The debris flow of Shaofang gully,Hongchun Gully and Mozi gully can block the Minjing river under the 10 years return period precipitation.The debris flow of Er gully and Taiping gully can block the Minjing river under the 5 years return period precipitation.The assessment result agrees with the phenomena of field investigation and can provide scientific supports for the prevention,elusion and mitigation of debris flow hazards and reconstruction project in the earthquake area.