Research On The Flood Control And Waterlogged Elimination Of Huiji River In Kaifeng City Based On HEC-RAS

There are large areas of plain depression zone in china, which leads to high frequency of flood and waterlogging disaster due to the typical characteristics of topography. Especially in Huai River Basin, the total waterlogging areas reach100thousand km2, including100million mu of farmland. The study area, part of Huiji River Basin, is located in the Eastern of Henan Province, belonging to Huang-huai plain, in which the soil texture of plain depression is good to farm and the chief crops are wheat and corn, being one of the major grain producing areas. According to incomplete statistics of pertinent data in Huai River Basin during the period of1991-2007, the areas affected by water-logging amount to7260thousand mu, while the annual average inundated areas reach427thousand mu, which account for24percent of the research area. Over the years flood disaster has become the bottleneck to production and life of local farmers, therefore the Huiji River depression zone, especially the mainstream section of Huiji River must be regulated as soon as possible, in order to solve fundamentally the problem of water-logging in the basin. Considering this, based on the project of comprehensive treatment in the mainstream section of Huiji River in Kaifeng City, the HEC-RAS model was introduced. Some research work was completed as follows.(1) Based on HEC-RAS, digital river channel and flood plain models reflecting the current situation of the Huiji River in Kaifeng City were developed using178cross sections measured data of the river channel.(2) According to the river channel and flood plain models, existing problems related to the river channel were evaluated. The results show that the level of the riverbed appears high and the width is narrow generally; the river slope is asymmetry and unsteady; the bottom of the river channel is uneven and severe deposition, obviously reducing flood drainage capability of the river channel.(3) The water level under the condition of design flow once in a5or20years for various cross sections was simulated respectively. The results indicate that the water level is70.97-58.94m during the design flow once in a5years, while the water level is71.58-59.77m during the design flow once in a20years.(4) The size of typical sections in river dredging project and the elevation of levee top in levee realignment project were determined on the basis of the hydrodynamics simulation results of design flow once in a5and20years respectively. The governance effects of river dredging project and bank regulation project were analyzed and evaluated depending on HEC-RAS model. The water level under the condition of design flow once in a5years reduced0.6～1.91m, with an average of0.93m, while the water level decreased0.18～1.73m, with an average of0.60m, under the condition of design flow once in a20years. This project could effectively increase capability of flood control and drainage of Huiji River in Kaifeng City.