都江堰龙溪河流域典型泥石流物源演化特征遥感监测

Dynamic Evolution Characteristics of Material of Typical Debris Flow Using Remote Sensing Technology, in Lonngxi Catchment,Dujiangyan, China

2008年"5·12"汶川地震致使都江堰龙溪河流域产生了大量的碎屑体,为震后暴雨泥石流的发生提供了丰富的固体物源物质。2010年8月14日,都江堰龙溪河流域暴发大型泥石流,堵塞龙溪河致使河水改道,威胁城镇居民的生命财产安全。为研究泥石流物源的演变特征,选取5条泥石流及覆盖其范围的5期高精度影像,结合野外详细调查,通过ArcGIS空间分析发现,地震前这些泥石流流域内植被良好,未发现大规模的地质灾害,均属于清水沟。汶川地震后崩塌滑坡体的面积由震前的0.10万m^2增加到地震后的41.28万m^2,崩塌滑坡个数由震前的1个增加到汶川地震后的283个。2010年"8·13"泥石流后,受降雨地表径流的冲刷侵蚀作用影响,部分崩塌滑坡扩大及新产生,经统计研究区泥石流流域内扩大及新增滑坡个数47处,崩塌滑坡体的面积在暴雨后与地震相比增加了8.29万m^2,比例达16.72%。同时经过5期新增及扩大崩塌滑坡体增长率的统计,发现随着时间的推移其增长速度逐年降低,有力证明了震后研究区泥石流内崩塌滑坡体逐步稳定,生态环境得到有效恢复。

After‘5·12’Wenchuan Earthquake,the massive loose solid matters were produced in Longxi River,Dujiangyan,which provides the rich materials for debris flows.On 14 th August,2010,debris flows occurred in five valleys,which thrust in farmland and jammed the Longxi River diversions,threatened the old Longchi town.In order to research the dynamic evolution of source,we selected five debris flows as study examples and five high precision image covering the study areas,compared the evolution characters of the valleys by ArcGIS.The results indicated that:before‘5·12’earthquake,the study area cover was good,geologic hazards were not found,the basin stream all belonged to the clear ditch;after‘5·12’Earthquake,the number of landslide was 283 and the area was 41.28 hm^2;after‘8·13’debris flow event,the number of landslide was 47 and the area was 8.29 hm^2 due to rainfall,surface runoff scouer erosion,expansion and new generation of partial collapse and the landslide.After five periods of high resolution remote sensing interpretation of the landslides,the growth rates of landslides were declining year by year,the ecological environment gradually recovered.