基于GIS的山洪灾害风险区划

通过探讨应用地理信息系统技术编制山洪灾害风险区划图的方法。以1：25万地理底图为基础，对影响山洪形成与泛滥的地形坡度、暴雨天数、河网缓冲区、标准面积洪峰流量、泥石流分布密度和洪灾历史统计六项因子进行了分析和叠合评价，完成了红河流域的山洪灾害危险评价图。以人口密度、房屋资产、耕地百分比、单位面积工农业产值作为指标进行了易损性分析，并借助于GIS分析工具，将危险评价图与易损性图进行叠加分析，完成了红河流域的山洪灾害风险区划图。区划结果表明GIS方法能够有效地对影响山洪形成与泛滥的因子数据层进行空间集成分析。该风险区划图可通过对山洪易泛区的不同风险地带的土地利用规划的决策而减轻山洪灾害；此外，也为山洪易泛区的居民提供有关山洪风险信息。

A GIS Based Regional Torrent Risk Zonation

This paper explores the methodology for compiling the torrent hazard and risk zonation map by means of GIS technique for the Red River basin in Yunnan province of China, where is vulnerable to torrent floods. Based on a 1:250,000 scale digital map, six factors including the number slope angle, rainstorm days, buffer of river channels, maximum runoff discharge of standard area, debris flow distribution density and flood disaster history were analyzed and superimposed to create the torrent hazard risk evaluation map. Population density, farmland percentage, house property, and GDP as indexes accounting for torrent hazards were analyzed in terms of vulnerability mapping. Torrent risk zonation by means of GIS automatically was overlaid on the two data layers of hazard and vulnerability. Then each grid unit with a resolution of 500 m × 500 m was divided into four categories of the risk: extremely high, high, medium and low. Finally the same level risk was combined into a confirmed zone, which represents torrent risk of the study area. The risk evaluation result in the upper Red River basin shows that the extremely high risk area takes up 17.9% of the total inundated area of 13 150 km², the high risk area is 45.9% of 33 783 km², the medium is 25.2% of 18 563 km² and the low risk is 11.0% of 8115 km².