白龙江舟曲段泥石流孕灾条件及发育特征分析

Analysis on disaster-inducing conditions and development characteristics of Debris Flows in Zhouqu of Bailong River

白龙江流域舟曲段是泥石流灾害高易发区和重点防治区,掌握该区泥石流的孕灾背景条件及发育特征对泥石流灾害防治具有重要现实意义。基于白龙江舟曲段241条泥石流调查数据,从地形地貌、地层岩性及致灾岩组、地质构造、降雨及人类工程活动等方面分析了泥石流孕灾背景条件;应用数理统计的方法,从流域面积与主沟长、沟床比降与相对高差、泥石流沟完整系数、重点泥石流沟发展阶段4个方面探讨了泥石流发育特征。研究结果表明:(1)舟曲段泥石流流域面积小于20 km^(2)占泥石流总数的89.2%,主沟长度主要集中在1~5 km,沟床比降200‰~500‰占泥石流总数的60.2%、大于500‰占泥石流总数33.2%;(2)泥石流相对高差主要集中在500~2000 m,泥石流流域形态主要为长圆形和椭圆形;(3)21条重点泥石流沟均处于幼年—壮年期,潜在危险性巨大。

The Zhouqu section of the Bailong River basin is a high-risk area and a key control area of debris flow disasters.It is of great significance to master the disaster-inducing conditions and development characteristics of the debris flow in this area.Based on the data of 241 debris flows of this area,analyses are made of the disaster-inducing conditions in terms of landform,lithology,disaster-causing rock formation,geological structure,rainfall and human engineering activities.The development characteristics of the debris flow is also analyzed by means of mathematical statistics in four aspects including basin area and main gully length,gully gradient and relative height difference,debris flow gully integrity coefficient and key debris flow gully development stage.The research provide important data support for debris flow disaster prevention and control,territorial space planning and ecological civilization construction in the Zhouqu Section of Bailong River.The results show:(1)The debris flows basin area of Zhouqu section is<20 km^(2) accounting for 89.2%,the ratio drop of ditch bed is from 200‰ to 500‰,accounting for 60.2%,and those >500‰ accounting for 33.2% of the total debris flow in the study area;and the length of the main gullies is from 1 to 5 km.(2)The relative height difference of the debris flow mainly concentrates from 500 to 2000 m.The debris flow basins form is mainly long circular and oval.(3)The 21 key debris flow gullies are in the juvenile-maturity stage with great potential danger.