One Dimensional Hydrodynamic Flood Forecasting Model And Its Real-time Correction

It is difficult to describe the runoff generation and confluence characteristics scientifically and accurately because of the complexity of underlying surface in mountainous and plain mixed basin.Especially in the process of confluence,the shape of riverbed has a great influence on the evolution of flow in the river.The confluence part of the traditional hydrological model is difficult to deal with these problems,resulting in the final forecast is not ideal.At present,some commercial software can better solve this problem.However,due to the limitation of software,secondary development and integration into flood forecasting and dispatching system are not possible.In this paper,based on the development of the joint forecasting and operation system of four major reservoirs in fomo Baixiang reservoir of Pi River Basin in Anhui Province as the background,the integrated hydrodynamics coupling model is established in the system,which provides the basis for flood impact analysis.The main research contents and achievements are as follows:(1)In this paper,a one-dimensional hydrodynamic model based on the finite difference Preissman four point eccentric implicit scheme is used to construct a river network model which is in line with the characteristics of the Pi River Basin.The basic principle of the model,the construction method of the river network,the treatment method of the inner boundary and the solution method are analyzed in detail.The derivation process of the catch-up coefficient of the inner boundary of the sluice weir in the annular river network and the response to the riverbed are expounded The method to improve the stability of the model by alternation of drying and wetting.(2)A general hydrodynamic model software suitable for tree and ring river network is developed.The program is programmed with C language,and the source code is more than 6500 sentences.(3)Through analysis and calculation,it can be seen that the inflow has great influence on the flood process of Pi River.Because of the difficulty in obtaining the interval inflow,it is feasible to use the method that the interval inflow predicted by Xin'anjiang model is evenly distributed to each reach according to the length of the river channel,and the time of the interval inflow is moved forward to reflect the confluence process of the interval inflow.(4)Four floods occurred in recent years were used to verify the model.After debugging,it is considered that: for Pi River Basin,when the inflow time of foxiangheng interval is moved forward by 9 hours,the calculated flood process of the model matches the actual flood process with high matching degree,which can meet the needs of forecasting work.The results have been used in the flood impact analysis module of Pi River Basin.(5)The conditions of runoff yield and concentration are different in different watersheds,and the method of moving forward Interval inflow time has limitations.Considering the generality of the model,a real-time feedback correction method for interval inflow is proposed in this paper.The accuracy of prediction is improved through the correction calculation of flood in Pi River Basin.This method is an effective and simple correction method.