基于GIS和RS技术的北京市功能区产流风险分析

Research on potential runoff risk of urban functional zones in Beijing city based on GIS and RS

城市化进程加大了城市区域暴雨洪水灾害发生的风险,定量研究城市降雨产流特征,可以为城区的科学规划和管理提供科学依据。以北京市五环内地区为研究对象,利用GIS和RS技术提取了五环内的土地覆被信息,并结合不同地区用途进行了功能分区。在此基础上,结合SCS-CN水文模型分析了研究区在不同降雨重现期的降雨产流分布特征,并定量识别了北京市五环区域内的产流风险区。结果表明:在不同重现期降雨下,五环内地区不同等级产流风险区分布格局差异明显。高产流风险区占全区的面积由重现期1 a的18.90%增加到重现期100 a的54.74%;由于不透水面比率不同,不同功能区的产流特征也存在显著差异,其中商业用地区产流风险最高,平均产流量为24.76mm(重现期1 a),天然绿地区产流量最低,均值为7.36mm(重现期1 a);随着降雨重现期的增加,各功能区之间的产流量存在趋同效应;五环内产流风险格局呈现出中心高、四周低的环状分布特征,高产流风险聚集区大多分布在城市中心的商业和居住区,低产流风险聚集区主要为大型公园和天然绿地,分布在四环与五环之间。城市防涝规划工作应该充分考虑城市产流风险聚集区分布以及不同功能区的降雨产流风险特征,分层统筹,科学拟定规划方案,同时还要充分利用城市自身的"生态"优势,多角度解决城市暴雨洪水问题。

Urbanization has increased the risk of urban flood. Quantitative research of urban rainfall-runoff process, can provide a scientific basis for the scientific planning and management of the city. In this paper, the land use/cover data and urban functional zones within Beijing five-ring areas were classified with the aid of GIS and RS technology. The SCS-CN method, as a traditional empirical model in the fields such as surface hydrology, was selected for simulating the surface runoff potentials within different urban functional zones in this study. Meanwhile, we analyzed the distribution of the surface runoff under different return periods of precipitation. Then the index of Moran＇s I was used to recognize the “hot spots” and “cool spots” of surface runoff in Beijing five-ring areas. The result showed that, the distribution configuration of surface runoff experienced a remarkable difference under different return periods of precipitation. The area of high runoff potential regions increased from 18.90% to 54.74% across the whole five-ring areas when seeing 1-year and 100-year return periods of precipitation respectively. Due to the difference and diversity of the impervious surface rate, runoff risks differed significantly from each other across different urban functional zones. For example, the highest risk of runoff generation was captured in the commercial zone by the hydrological model, with an average of 24.76 mm under 1-year return period of precipitation. The preserved zones, on the other hand, had the lowest risks of runoff generation （7.36 ram）. Furthermore, the potential risk of runoff depth became similar to the increase in precipitation return-period. Finally, the spatial cluster of various runoff risk zones was captured by using spatial autocorrelation analysis method. In general, runoff risk zones experienced a circular pattem, which decreased from the central to the peripheral region. In most cases, the commercial and residential zones located in the core area of the city were prone to higher runoff generation and risks. Large parks and natural green areas, on the other hand, can help to minimize the flooding risk, and thus can be treated as the low-risk zones. These zones are mainly situated within the fourth to fifth-ring road areas of Beijing city. In order to remit the flooding hazard, city administrators should take account of the distribution of runoff risk area and rainfall-runoff characteristics of various urban functional zones before the relevant regulations were formulated. And also the ecological advantage within the city should be made full use of to solve the urban flooding hazard.