四川泸定县泥石流灾害成因、特征与防治建议

泸定县地处川西高原与四川盆地的过渡地带,地质环境条件复杂,分布泥石流沟127条,发育密度054条·10km-2。在遥感解译和地面调查基础上,论述了泸定县泥石流灾害成因、发生特征、危害和发展趋势,提出了相关防治建议。(1)成因表现为复杂的断裂构造导致流域内松散物源丰富,较大的相对高差提供了良好势能条件,而汛期集中强降雨则提供了动能条件,且雨量条件中当日雨量与前期有效降雨量之间具有幂函数关系; (2)发生特征表现出典型的空间群发性(包括2005-06-30群发性泥石流、2005-08-11群发性泥石流和2006-07-14群发性泥石流)与时间的夜发性; (3)危害方式主要包括淤埋、冲毁、侵蚀、堵河4种,泥石流已造成74人死亡; (4)发展趋势表现为泥石流沟多处于形成期和发展期(113条,占89%),发生的年际准周期由20a缩短至不足10a,且发生条(次)由4条(次)增加至44条次(2005年); (5)泸定县泥石流防治的突出问题表现为城镇泥石流问题、泥石流堵塞主河问题、风景区泥石流问题与冲沟泥石流问题,建议通过科学规划、风险防御体系构建、土木工程治理、监测预警等措施予以防御。

FORMATION, CHARACTERISTICS AND PREVENTION ON DEBRIS FLOW HAZARDS IN LUDING COUNTY, SICHUAN

As located at the transition terrain between Tibet Plateau and Sichuan Basin,Luding county is typical of complex geological envirnonment and 127 debris flow gullies are distributed in this county with a formation density of 054 gully·10km-2. On the basis of RS interpretation and field investigation,the forming,characteristics,damages,developing trend were discussed and corresponding prevention advices were put forward.(1)Complex geological,steep geomorphology and intense rainfall supply enough loose solid materials and advantageous potential and kinetic energy to debris flows. Whats more,an obvious power law relationship is existed between the intraday rainfall and former six day antecedent effective rainfall.(2)Debris flows are typical of group occurrence(including 2005-06-30 event, 2005-08-11 event and 2006-07-14 event)as occurrence space is concerned and night occurrence as occurrence time is concerned.(3)Burying,bursting,eroding and blocking consist of the main damage mode of debris flows and 74 residents had lost their lives because of debris flows in history.(4)Most debris gullies are at the forming stage and developing stage(113 gullies, 89%)and the annual period has been shorting from 20 years to less 10 years but the occurrence times have been increasing from 4 to 44 on the contrary.(5)Town debris flows,blocking of debris flows,scenic spot debris flows and ravine debris flows are four main prevention problems in Luding county and corresponding prevention advices were put forward including scientific planning,constructing of risk mitigation system,engineering,monitoring and warning. 