太湖流域洪涝灾害淹没范围模拟

Submerged Simulation of Flooding and Waterlogging in Taihu Watershed

平原水网地区多属大河三角洲地区， 也是经济最发达的地区， 当遭受洪涝灾害后， 经济损失极为严重。研究以太湖流域为例， 采用河网非恒定流计算方法， 分析洪涝的发生过程， 并结合地理信息系统， 模拟洪涝的淹没范围， 为及时掌握洪涝灾情， 制定防洪减灾决策提供依据。

Plain with river network regions are generally located in great river delta, in which they are usually the most developed in China. However, the economic loss could be much severe if they are suffered flood and waterlogging disaster. According to numerical model of river network unstable flow, the present paper analyses the flood generating process in Taihu Basin. Furthermore, the submerged area of flood and waterlogging in the Basin is simulated with geography information system (GIS). It has reasons to believe that it is useful to provide scientific basis for mastering the flood and waterlogging disaster and making decision on flood prevention and flood disaster reduction. There is a great variety of landscape exists in Taihu Basin, including mountains, plains, lowlying dykes, rivers and lakes. However, the runoff formation mechanics is different for different topographical conditions. Furthermore, the space time distribution of precipitation in the Basin is non uniformed because of the large basin area. Therefore, 34 precipitation runoff polygons or units are divided according to hydrological data for years in Taihu Basin. Each polygon is further divided into three topographical types according to their topographical conditions, e.g. water surface, paddy field, and dry land. This paper calculates the discharge of each topographical type with different time interval based on the runoff formation mechanics of these three topographical types. Considering the discharges and their area percentage of different topographical type, the discharge of each precipitation runoff polygon with different time interval is figured. The Taihu Basin has complicated river network because of its rivers and lakes that spread all over the Basin. This paper puts the Basin two basic parts, that is, mountain part and plain part. In mountain part, 13 sub basins are conceptualized. Flow concentration is simulated according to instantaneous unit hydrograph method in these sub basins. At the same time, 419 rivers, 13 lakes and 267 nodes are conceptualized in plain part. A plain with river network model is constructed and flood movement in river network is simulated according to the numerical model of river network unstable flow. In practical simulation, except 13 mountain sub basins whose flow concentrates at a certain node, the discharge of plain and river network is symmetrically drained into river networks around according to the discharge of precipitation runoff polygons and their drainability. The discharge can not drain timely stops in lowlying dykes, which is regarded as submerged runoff. Based on the constructed hydrological model in Taihu Basin, this paper constructs the digital elevation model (DEM) of Taihu Basin based on GIS. Furthermore, it is overlapped with grid precipitation runoff polygons. According to the simulated waterlogging discharge in each river network polygon, the largest submerged area in Taihu Basin in 1991 is simulated (Fig.4). The simulation has higher precision comparing to the practical submerged area of the Basin.