美姑河流域公路泥石流物源成因

Research on Material Sources of Forming a Debris Flow along Highways in the Meigu River Basin

位于四川西南部横断山区东部边缘大凉山内部的美姑河流域是我国公路泥石流典型发育的地区之一,泥石流具有规模大、致灾作用强烈、活动频率高等特点.从流域地貌景观、新构造应力场及具有焚风效应的大气环流特性出发对区内公路泥石流成因进行了深入分析,获得了地貌景观造就了流域内地表植被稀少、焚风效应显著、泥石流沟轴向与新构造应力场两个剪切带方向一致(相差5.2°～6.5°)的结论,泥石流发育规律符合地貌发育对抗性原理[1].作为典型事例,把洛高依打泥石流的物源区分为不稳定物源区、基本稳定物源区和稳定物源区,并首次将物源补给量与不同降雨频率相结合,获取了不同降雨频率(3～5 a一遇、10 a一遇、20a一遇、50 a一遇和100a一遇)泥石流最大可供物源量.对公路泥石流研究及治理中一些关键问题进行了探讨.

The Meigu River Basin, locating in Daliang mountain region in southwest Sichuan province, is one of typical areas to develop debris flow along highways in China. Debris flow there have some features such as giant scale, strong hazard and high frequency. Based on landform, neotectonic stress field and atmospheric circulation with extreme foehn effect the authors deepIy approach the formation reason of debris flow along highway in the basin, further present some important conclusions, i.e. special landform make rare plants in the basin, obvious foehn effect and the same distribution direction （only deviation 5.2°- 6.5°） between longitudinal debris flow valley and shear zones of neotectonic stress field, which identify that development features are consistent to the principle of antagonism. As an example, material source of Luogaoyida debris flow is divided into three areas in the paper, i.e. unstable material area, limit stable material area and stable material area. As the first time material provision is together with various frequency precipitation （one time in three or five years, one time in ten years, one time in 20 years, one time in 50 years and one time in 100 years ）, the most possible material provision are obtained. In the end, some key problems in research and control of debris flow along highway are discussed.