山丘区小流域沟道洪水演进数值模拟研究

In recent years, flashfloods have occurred frequently in the gully regions of small-scale watersheds. They have caused a great deal of damages to the local economy and properties. In order to prevent and control mountainous flashflood disasters, accurately forecasting and early warning of this kind of flashfloods is particularly important. However, it is very difficult to simulate the flashflood evolution in the gully regions because of the lack of controlling cross section information and observed flashflood data in the regions. To overcome these problems, firstly, the generalized orientation of a river or gully was obtained based on the DEM data of the study region. In order to determine the channel width and depth, an applicable selection criterion of two channel width formulas are proposed according to the theory of river network classification and the concept of stable river width. Secondly, a coupled model of one and two dimensional (1-2D) flashflood routing was developed based on the theory of diffusive wave to improve the simulation efficiency and to solve the easily overlanding problem due to irregular and small size of the gully. In order to verify the accuracy and efficiency of the coupled 1-2D model, a case study was conducted at the Manshui river-basin in Fangshan District of Beijing city, and the simulated results of the coupled 1-2D model were compared with those of the 2D shallow water model and the observed data. The results indicate that the coupled 1-2D model has a reasonably high accuracy which is almost the same as that of 2D shallow water model in the aspects of flashflood discharge, water level, total volume and peak arrival time. In addition, the simulating efficiency of the coupled 1-2D model is higher than that of 2D shallow water model, which implies the coupled 1-2D model is much more suitable for the numerical prediction and early warning of flashfloods than the 2D shallow water model in small scale watersheds.