龙门山地区震后泥石流灾害区域预警研究

Regional Warning of Debris Flow Hazards after Wenchuan Earthquake in Longmenshan Region

5·12汶川地震造成大量松散堆积物，导致震后触发泥石流的极端降雨量比震前显著降低．在龙门山地区震后泥石流发育特征分析的基础上，探讨了震后触发泥石流灾害的区域降雨阈值及其地域差异性，震后触发泥石流的72小时雨量分布特征为：映秀-汶川一带为75～100mm，茂县-北川一带以100—160mm为主，上述区域外围及平武-青川一带为160～200mm；在龙门山前的雁门-茶坝、龙门山后山的禹里-平武之间为200mm以上．综合考虑地震地质、地形地貌和降雨等因素，建立了地震扰动区泥石流预警指标体系．采用加权信息量模型完成了龙门山区泥石流易发性评价，然后采用年最大72小时降雨量为主要触发因素，开展了震后5年的泥石流危险性预测评价及区域预警研究，提出泥石流的区域危险性是动态变化的，高危险区主要随降雨量和松散堆积物空间分布而变化，为震后泥石流灾害气象预警和防范等提供了依据．

Massive loose deposits caused by the Wenchuan earthquake on May 12, 2008 have resulted in significant decrease of rainfall threshold of post-earthquake triggering debris flow in comparison with pre-earthquake level. Based on the post-earthquake debris flow characteristics analysis in the Longmenshan region, the regional rainfall threshold of triggering debris flow and its regional differences were discussed. The 72-hour rainfall distribution characteristics of post-earthquake triggering debris flows are as follows ： 75 - 100 mm in Yingxiu--Wenchuan area, 100 - 160 mm in Maoxian--Beichuan area, 160 -200 mm in around above regions and Pingwu--Qingehuan area, and 200 mm or more in Yanmen--Chaba area and Yuli--Pingwu area. Based on comprehensive analysis of seismogeology, topographic and geomorphic conditions, extreme rainfall and regional characteristics of post-earthquake debris flows, the regional rainfall threshold of triggering debris flow, as well as the warning index system, for earthquake-stroked region was established. The weighted information model was adopted to complete debris flow susceptibility assessment in the earthquake-stroked Longmenshan region. Thenng the annual maximum 72-hour rainfall as a main trigger regional warning study in 5 years after the Wenchuan earthquake were conducted.