Research On Stage Forecasting Model For Tidal River Based On Diffusion Wave And Bi-Directional Wave

Current in tidal river shows a complex periodic characteristic, and it is unsteady flow moving alternately backward and forward. Compared with inland river, the flow in tidal river has more controlling influences, mainly coming from ocean tides, density current caused by runoff mixed with sea water, and storm surges along coast. It has been shown that the description of mechanism consisting of all above characteristics turns out extremely complex. Moreover, a hard access to terrain data adds difficult to the stage forecasting for tidal river. Estuarine areas in China are prosperous, where highly suffer severe floods too.In order to make the job of flood control prompt and effective, a sophisticated mathematical model of stage forecasting for the tidal river cries for solution. Therefore, this research has quite practical value for flood control in estuarine areas.The account of this paper is summarized as follows. Based on the previous research, the development of stage routing model for tidal river was reviewed, the principles was outlined. And the technique features of application for the models have been achieved through stage simulation in the real rivers. Then, the feasibility of establishing stage forecasting model for tidal rivers was discussed.First, by reviewing kinds of river stage routing models, this paper laid special stress on analyzing two stage models, one was based on analytical solution of linear diffusion wave, and the other was bi-directional wave model.In the research, rationality of these two models for tidal rivers was discussed, meanwhile, some improvement was given if tributary or interval runoff exists.Then, with the previous findings, addressed how the model parameters influence the simulation results.Secondly, two stage routing models, one was based on diffusion wave and the other was bi-directional wave, for tidal rivers have been established, by making a thorough study of three tidal rivers, named Xinyi He, Nanxi Jiang, and Feiyun Jiang, The simulation results of the two models for the three tidal rivers proved a well reliability and applicability. Since the lack of terrain data, this paper is intended to find an effectively solution of channel simplification; since the different grades of flood, investigate water level classification; since the different conditions of lateral inflow, analyze its affection.Thirdly, according to the objectives and principles of flood forecasting system, made a try to develop a stage forecasting system for tidal river at Shangtang station and Mayu station, employed Xin'anjiang model to predict rainfall runoff.The aim of the research is to find a stage model for tidal river, which is simple, with clear physical concept and good results, and helpful to the stage forecasting job.