Research On Hydrological-hydrodynamic Model And Its Application In Flash Flood Forecasting

Flood disaster is one of the major natural disasters that constrain human social and economic development.Affected by topography,hydrology,meteorology and other factors,flood disasters occur frequently in small and medium-sized river basins in southwestern China,and have become the key deployment areas for flood control and disaster reduction.The flood disaster situation in the Longxi River Basin in the north of Chongqing City has been severe in the past 40 years.How to further strengthen flood forecasting and establish a sound flood control project system based on wetlands and reservoirs in the basin is an important research topic for flood control in the Longxi River Basin.The main method of basin flood forecasting is to establish hydrological model and hydrodynamic model,and to simulate the process of runoff generation,confluence and flood evolution.This paper combines the advantages of hydrological model and hydrodynamic model,and establishes a hydrological-hydrodynamic model,which is applied to the flood simulation of Longxi River Basin under different rainstorm return periods.The discharge curve calculated by the hydrological model is used as the inflow boundary condition of the hydrodynamic model.The flooding situation of the basin is reflected in the form of two-dimensional flood submerged map,which provides important basis and reference for the development of flood prevention.Wetland construction management is a major component of integrated river basin management.Due to the ability of water-soil conservation and flood storage,the wetland has a positive effect on mitigating the degree of flood inundation in the watershed,but the significance of the effect is affected by the geographical location,water storage capacity and soil type of the wetland.The effect of wetlands is necessary to be specifically analyzed according to the actual situation of the basin and wetlands.Based on the hydrological-hydrodynamic model,this paper quantitatively studies the flood control effect of the Shuanggui Lake wetland and surrounding reservoirs in the Longxi River Basin.The results show that the flood mitigating effect of the wetland on the upstream is significantly larger than that in the downstream.The flood reduction effect in key flood control areas,such as Helin Town,Liangping District,is obvious.The research on the flood control function of wetlands has practical reference value for the river basin management department to make full use of natural resources to plan and deploy flood control work.The Shizitan Reservoir is the largest reservoir in the Longxi River Basin and is responsible for the flood control of downstream river,power stations and rural factories.Using the latest measured storage capacity curve,the current flood control scheme of the Shizitan Reservoir is reviewed,and a new flood control scheme with a 0.5 m-increase of flood limit level is proposed.Through the flood regulating trial,both schemes meet the flood control requirements of the reservoir and the downstream river.The 2D HEC-RAS model is used to simulate the flood evolution in downstream channels under different flood return periods.The flood submerged maps of the river and floodplain are obtained.On the basis of meeting the flood control requirements,the new flood control scheme will help to improve the social and economic benefits of the Shizitan Reservoir and provide reference for the formulation of flood control schemes.