面向城市平原地区暴雨积涝汇水区分级划分的方法研究

Research on Classification of Rainstorm Watershed Delineation Approach for Plain Urban Regions

汇水区划分是分布式水文模型计算的基础。针对现有方法使用DEM在平原城市地区划分的汇水区不符合实际地形情况,本文提出了一种面向城市平原地区分级划分汇水区的技术方法。该方法从城市用地分类角度出发将城市分为中心城区和郊区,依据城市排水主干水系进行汇水区一级划分,将影响中心城区和郊区的不同径流因子分别融入DEM中,利用细化的DEM进行二级汇水区划分;在此基础上,根据实际汇流情况,结合Voronoi图,对中心城区进行三级划分,最后通过GIS技术进行修正。该方法既结合了传统DEM生成子流域的算法,又融入了城市区域地物地貌特点,能更好地满足城市地区的需要。选择上海市嘉定区西北部地区为实验样区,利用该方法进行汇水区划分比较表明,其对于城市平原地区具有很好的适用性。

The compartmentalization of urban rainwater catchment basin is an initial step in the application of spatially distributed hydrological models. Traditional watershed delineation approach has a better application in the plain region where less human activities are involved. However, in the flat areas of city it cannot get a correct watershed boundary and accurate watershed delineations. The realistic fiver network and watershed boundary may not always be derived from conventional DEM processing methods. In this paper, in order to reflect the city morphologies and represent the real situation of drainage network, a new method is proposed based on city classification and anthropogenic land cover features that influence the drainage patterns. According to the city drainage system and urban land classification, this method divides the city into the inner-city and suburban neighborhoods. According to the ability of fiver catchment, we take the rainwater catchment basins into lower divisions, and then find the anthropogenic land cover features that influence the convergence of the inner-city and suburban neighborhoods. To downscale the DEM and extract drainage structures and watershed boundaries with improved accuracy, we take the anthropogenic land cover features （i. e. roads and streams, buildings, some pond and drainage networks） into the DEMs, divide the catchment basin based on D8 algorithm and modify the catchment areas using Thiessen polygon. The results show that the method is effective and matches well with the real situation of city, which not only take the advantage of anthropogenic land cover features, but also combine with the spatial distribution of urban drainage facilities. The method is applied to a watershed in the Shanghai Jiading drainage basin based on high accuracy DEM and topographic river map, and we compare the proposed method with traditional methods. The results show that the proposed method has a good applicability for the plain urban areas and is able to produce more realistic results. Above all, we conclude that this method is effective and easy to implement.