Study On Flood Control Capacity Improvement Based On Hydrodynamic Model ——Take Nanhe River Basin In Chengdu As An Example

Frequent floods occurred in the middle and lower reaches of the Nanhe River in Sichuan province southwest of Chengdu.To solve this problem,a two-dimensional coupled hydrodynamic model was constructed by using the flood analysis software IFMS.The model is used to evaluate the current situation of the flood control system in the Sanjiang area of Nanhe River.After assessing the current situation,Ten engineering schemes for upper storage,middle stagnation and lower drainage were put forward.Ten schemes were evaluated by constructing a two-dimensional coupling model.In the end,Eight of them were recommended for the Sanjiang area of Nanhe River.The recent schemes include expanding Changtan reservoir in the upper reaches of Pujiang River,constructing three dam reservoir in the upper reaches of Chu River,constructing central lake and ecological wetland in Shouan,setting up flood detention project in Sanjiang area,demolishing and renovating Tongji weir in the lower reaches of Nanhe River and dredging and regulating these six schemes;The long-term plan is to build Shuikou reservoir in the upper reaches of Nanhe river and Heming reservoir in the upper reaches of inclined River on the basis of the recent plan.And it turns out,(1)Under the current state,pujiang urban area,Qionglai urban area,Nanhe Sanjiang area and Xinjin urban area have higher risk of inundation in the face of flood.(2)The recent scheme can significantly reduce the flooded water level and flooded area in Pujiang urban area,Qionglai Sanjiang district and Xinjin urban area;Pujiang county can meet the standard of flood control once in 50 years;Villages and towns along the Sanjiang River can meet the standard of onein-a-decade flood control;Qionglai urban area and Xinjin urban area can meet the flood control standard of one in 20 years.Compared with the present situation,the inundation area of Nanhe river is reduced by 46.79%,36.59% and 20.63%,respectively,when it occurs once in 10,20 and 50 years.Compared with the current situation,the flood inundation area of Pujiang River will decrease by74.66%,74.01% and 58.44%,respectively,when it occurs once in 10,20 and 50 years.(3)Under the long-term plan,villages and towns along the river in Sanjiang Area can meet every 20 years;Qionglai urban area and Xinjin urban area can basically reach the 50-year flood control standard,and the flood control standard effect is very obvious.Compared with the recent scheme,the inundation range of Nanhe River is 28.92% and 19.27% lower than that of the recent scheme when the flood area of Pujiang River is 15.47% and 29.38% lower than that of the recent scheme when the flood area of Nanhe River is only once in 20 and 50 years.(4)Through the demolition and renovation of Tongji Weir and the dredging of the lower reaches of Nanhe River,the support of Jinma River to Nanhe River will be intensified,but it will not affect the effect of the overall scheme.And with the increase of flood flow of Nanhe River,the supporting effect of Jinma River on Nanhe River will decrease rapidly.