【作者】 崔鹏； 庄建琦； 陈兴长； 张建强； 周小军；

【Author】 CUI Peng~(1,2),ZHUANG Jian-qi~(1,2),CHEN Xing-chang~(1,2,3),ZHANG Jian-qiang~(1,2) ZHOU Xiao-jun~(1,2) (1.Key Laboratory of Mountain Hazards and Earth Surface Processes/Institute of Mountain Hazards and Environment,Chinese Academy of Sciences,Chengdu 610041,China;2.School of graduate university Chinese Academy of Sciences,Beijing,10049;3.School of Environment and Resources,Southwest University of Science and Technology,Mianyang 100037,Sichuan)

【机构】 中国科学院山地灾害与地表过程重点实验室； 中国科学院水利部成都山地灾害与环境研究所； 西南科技大学环境与资源学院；

【摘要】 2008年5月12日的汶川Ms8.0地震对地表产生强烈扰动,使得泥石流形成条件发生剧烈变化,影响到震后泥石流的活动特征和减灾对策。本文在调查数据的基础上,从固体松散物质条件、微地貌条件和水文条件的变化三个方面,分析了汶川地震区震后泥石流形成条件的变化,认为汶川地震灾区崩塌、滑坡等产生的松散固体物质达28×10~8m~3,为该区泥石流长期活动提供了丰富的物质基础;流域微地貌突变特别是严重的沟道堵塞,有利于泥石流规模的增大;强烈地表扰动和毁灭性、大面积毁坏植被,改变了地表水入渗、产流和汇流条件,利于侵蚀和洪峰形成。这些流域状态的巨变,构成了有利于泥石流形成的条件组合。从而,导致震后泥石流活动强度急剧增,使得泥石流成为对地震区影响最为严重的灾害。震后泥石流活动的主要特点有:泥石流沟谷数量增加,大量震前被判定为非泥石流沟的流域暴发了泥石流;激发泥石流的临界雨量明显降低;泥石流暴发表现出明显的高频性与群发性;泥石流的容重约提高10%-30%,原来定性为稀性或过渡性的泥石流沟转化为过渡性或粘性泥石流沟;泥石流流量普遍增大,大致可增加约50%-100%,现有规范中泥石流流量计算方法的结果偏小,需要修正。震后泥石流演变趋势为:活动强度由急剧增强的突变转为逐步减弱,期间流活跃期与平静期交替出现,第一个泥石流活跃期可能会持续约15年左右;泥石流形成将由降雨控制型逐步转为松散土体控制型;一些松散土体丰富且尚未发生泥石流的大于5km~2流域,将是未来暴发大规模泥石流的风险源。针对震后泥石流的活动特征、演化趋势和震区泥石流防治中存在的问题,提出了判识潜在泥石流灾害,增强减灾措施的针对性;进行泥石流灾害风险分析,加强风险管理;改进泥石流规模计算方法,适应震区超常规模泥石流防治需求;重新确定泥石流预警报的临界雨量指标,加强监测预警系统建设等灾害防治对策。更多还原

【Abstract】 On 12 May 2008.the ground surfaces have been suffered strong disturbance by the Wenchuan earthquake,which made the formation conditions of the debris flow to change dramatically.Therefore,the activity characteristics and prevention countermeasures of the debris flow after the earthquake are greatly affected.Based on the survey data,the change of formation conditions of the debris flow in Wenchuan area are analyzed from three respects which are solid loose materials,micro-topography and hydrological condition.Analysis suggests that the total of the solid loose mass generated by the collapse and landslides reached about 28×108m~3,which provides abundant material foundation for the long-term activities of the debris flow in this area.The mutation of microtopography is beneficial to increase the debris flow scale,especially the serious blockage of the channel.The conditions of the surface water infiltration,runoff and flow concentration are changed by the strong surface disturbance and large-scale destructive vegetation damage,which is beneficial to the formation of the erosion and flood peak easier.The great changes of the river basin constitute the conditional combination of the debris flow formation.Therefore,the activity intensity of post-earthquake debris flow increases rapidly and debris flow becomes one of the most serious risk source in disaster areas in future.The main active characteristics of the post-earthquake debris flow are as follows:(1) the number of debris flow gully increased,a large number of debris flows broke out in the watershed which was judged non debris gullies before the earthquake,(2) the critical rainfall that can induce debris-flow decreased significantly,(3) the debris reveals the characteristics of the high frequency and group-occurring,(4) the density of the debris flow increased by about 10%to 30%,the debris gully which was originally classified as turbulent or transitional transformed into transitional or viscous respectively,(5) the discharge of debris flow increased by about 50%～100%,and the results calculated by the current specifications methods are relatively small,which need to be amended.After earthquake,the characters of evolutionary trend of debris flow as follows:the activities intensity transformed into weakening from strongly with the active periods and quiet periods alternating and the first active period will last for 15 years;the trigger and control factor of debris flow convert from precipitation into loose material,the watershed with rich loose material and more than 5km~2 area is the most dangerous geo-hazards in the following years.According to the activity characters of debris flow,evolutionary trends and the shortage of debris flow prevention,we proposed the strategies for mitigation debris flow post-earthquake including that:discriminate the potential debris flow and enhance the pertinence of disaster reduction;risk analysis the debris flow hazards and strengthen the risk management for potential disasters; Improved the calculation method of debris flow magnitude to meet the mitigation requirements and strengthen the monitor and early warning system.更多还原