基于河网水系变化的水灾危险性评价——以永定河流域京津段为例

城市化过程中不合理的土地利用导致河道填塞、河网缩减现象普遍，城市水灾增加。基于灾害系统思想，构建了基于河网水系变化的水灾危险性评价体系，并以永定河京津段为例进行了实证分析。结果表明：（1）近40年来研究区水系结构简单化趋势明显，河道长度减少了20．5％，条数减少了36．4％，水系调蓄能力下降，在同样的致灾强度下水灾危险性加大；（2）在假设暴雨重现期为50年的条件下，经济密度差异决定了水灾潜在危险区的空间格局，居民用地将成为水灾重度危险区；平原段水灾重度危险区占5．7％，中度危险区占33．1％，滨海段重度危险区占13．9％，中度危险区占26．8％。研究结果可为区域综合减灾、水灾预报提供依据。

Assessment of flood hazard based on river network change:taking the Beijing-Tianjin segment of Yongding River watershed as an example

The unreasonable land use in the process of urbanization results in the frequent urban flood.According to the disaster system theory,this paper established the flood risk assessment system based on the river network change,and took the example of Beijing-Tianjin segment of Yongding River to make a case analysis.The results show that:(1) the river network structure appears as a trend from comprehension to simplicity.The length of rivers shortened 20.5% of that in 1968,and the river numbers decreased 79,accounting for 36.4%.This intensified urban flood risk in some degree.(2) Under the condition that the heavy rain return period is 50 years,economic density differences decided the spatial pattern of potential flood risk area.Resident land will become the severe flood risk area;potentially severe flood risk area in the plain region will account for 5.7%,moderate risk area will account for 33.4%;and potentially severe risk area in the coast will account for 13.9%,moderate risk area will account for 26.8%.The research can give reference to regional disaster reduction and flood prediction.