南水北调西线工程泥石流灾害及危险区划

南水北调西线工程是拟议中的国家重大建设工程,通过"五坝七洞一渠"共计260km的引水线路,引长江上游雅砻江和大渡河水入黄河。泥石流在工程区多有分布,现已查明,工程区共有不同危险度等级的泥石流沟103条。泥石流危险区划结果表明,研究区内没有泥石流极高危险区;泥石流高度危险区总面积为73km2,主要集中分布在杜柯河流域,达曲和泥曲流域有零星分布;泥石流中度危险区总面积114·75km2,各流域均有分布,其中杜柯河和达曲流域分布较多;泥石流低度危险区是分布最广的区域,总面积156·75km2,各流域均有分布,以杜柯河流域分布略多。研究表明,用单沟泥石流危险度值作为综合指标,以具有不同泥石流危险度等级的泥石流沟流域面积作为权重的加权平均方法,采用网格作为泥石流危险区划的基本单元,能够直接而真实地获得泥石流危险区划的成果。用本文提出的方法进行地质灾害的危险区划,无疑比用间接方法和替代指标得出的危险区划结果具有更高的可靠性。

Debris flows and zonation based on debris flow hazards in the area of the West-line Project of the South-to-North water diversion project in China

The west-line project of the South-to-North water diversion project in China has been planned since 1952. The huge project is planned to divert water from the upper reach of Yangtze River to the Yellow River. Debris flow hazards have been reported in the project area during the last decades. Based on a recent survey, there are 103 debris flow gullies with different ratings of debris flow hazard in the study area. The findings of regional hazards show that, there are no extremely hazardous debris flow gullies; but there are 73 km^2 of areas with a high hazard rating of debris flow; 114.75 km^2 with moderate hazard rating of debris flow, and 156. 75 km^2 with low hazard rating. Using the site-specific debris flow hazard rating as a composite index, weighted by the drainage basin areas with different debris flow hazard ratings, and based on grids, a direct method has been applied to the zonation of debris flow hazard in the study area. The zonation obtained by this method is better than those using indirect methods or replaced indexes. This method better reflects the regional hazard of debris flow in the project area.