5　Conclusion

In this paper,the combination of hydrologic model,sluice model and pump model,hydrodynamic methods is developed for simulating the rainfall-runoff process of the multi-level artificial controlled drainage systems in the Diaocha lake area,which is located in the middle reach of the Yangtze River.Through dividing the drainage area into a number of small sub-districts,the difficulty of hydrologic simulation will be simplified without sacrificing the simulation accuracy because that simpler model can be used to simulate the runoff of sub-district.In order to simulate the outflow of sub-district,the pump model of second-level pump station and sluice model of second-level sluice is developed.Similarly,in order to simulate the water level and flow in the main canal,the hydrodynamic model of drainage network is developed by using Saint-Vernan equations,using continuity equation and momentum conservation equation to simulate the water level and each way flow of the intersection,using hydraulic formula to simulate the first-level pump station or sluice.The outflow of subdistrict which is simulated using the pump model or the sluice model is coupled to the hydrodynamic model by the form of point inflow or distributed inflow.The case study show that the method developed for the flood simulation was successfully in the Hanbei river on the〝98+〞flood event in 2016.