城市山洪灾害风险评价——以云南省文山县城为例

山洪灾害风险评价对于减灾防灾决策和管理非常重要。本文介绍基于遥感和GIS方法的应用,探讨一种快速、简便而且较为准确的城市山洪灾害风险评价方法。以发生于1998年7月26日文山城20年一遇山洪灾害为实例,将GIS的数字高程模型与实测的山洪水位和洪峰流量结合进行淹没分析,研究表明采用该方法可以模拟准确山洪泛滥范围,并计算淹没水深分布。根据不同水深指标,应用GIS工具完成了山洪灾害危险分区。本研究利用高分辨率遥感影像提供承灾体类型的可靠和准确数据用于易损性分析和期望损失评估的价值计算。根据典型区财产损失的抽样调查,建立了不同承灾体类型与水深的关系,并确定其损失率;应用GIS空间数据处理和分析的集成方法完成了复杂的损失评估。在此基础上,按期望损失程度进行分区划分而完成山洪风险评价。研究结果表明基于GIS和RS方法进行山洪风险评价效果良好,值得推广应用于其他洪水泛滥区。

Urban flash-flood risk assessment: A case study inWenshan City, Yunnan

For the vulnerability reduction of mountainous cities affected by flood hazards, flash-flood risk assessment is very important for flood disaster mitigation measures. This paper explores a quick, simple and accurate GIS and RS based method for flash-flood risk assessment. With the flood for 20 return period occurring on July 26th, 1998 as a case, the study shows that through the inundation analysis carried out by combining DEM and actually observed floodwater level and maximum discharge runoff, the possibly inundated area can be accurately simulated and water depth distribution can be calculated within inundated area. Based on water depth index, flood hazard zonation was finished by using the GIS tool. This paper conducted cost calculation based on information of inundated ground objects acquired from remotely sensed image of high spatial resolution so as to provide the reliable and accurate data source for vulnerability analysis and flood expected damage estimation. According to the sampling survey for the property loss of the typical zones within the inundated area in 1998, this study established the relationship between different flooded object types and floodwater depth, and defined flood damage ratio on this basis. The adopted new methodology, namely the integration with the function of GIS spatial data processing and analysis greatly simplified the complex damage estimation and improved its accuracy. Flash-flood risk assessment can be completed by dividing the expected degree of loss due to potentially damaging phenomena. The study results show that the GIS and RS based method performs well in flash-flood risk assessment, thus it can be widely used for other inundated areas.