Analysis Of River Bed Evolution Characteristics Under Conditions Of Urban Waterscape Project Construction

Weihe River is the largest tributary of the Yellow River,its typical hydrological characteristic is the lack of water and the much of the sediment.The average annual sediment content is above 10kg/m~3,and it belongs to a multi silt river.When constructing urban water conservancy landscape projects on sediment-laden rivers,the sediment problem will be the difficulty of the key technology.This problem is mainly divided into the following two categories.One is the impact of siltation on the proposed water conservancy project,and the other is the impact on the erosion and deposition of the river after the completion of the project.If it is not studied,it will affect the service life of the project,and it will even adversely affect the urban flood control.Therefore,the paper took the reach of Xianyang city section of Weihe River as the research object,and through the methods of data access,field investigation,and numerical simulation,studied the influence of the gas shield dam on the erosion and deposition of the Weihe River,provided the control plan for the gas shield dam,to ensure that the project will maximize its effectiveness and ensure urban flood protection.The main achievements of this paper are as follows:(1)Through the analysis of the water and sediment data of the Weihe River for many years,the results indicated that the changes of water and sediment in the basin were the result of the joint action of climate change and human activities,besides,the trend of water and sand changes was consistent.(2)Based on the actual measured cross-section data over the years,the changes in the erosion and deposition of the riverbed before and after the completion of the?Xianyang river Lake?project were analyzed.The results showed that the riverbed was basically balanced before the construction?Xianyang river Lake?project.Except for a slight siltation in the section of Xianyang hydrologic station,the other sections were mainly eroding.After the construction of"Xianyang Lake"project,the channel was mainly scouring,and the river bed was undercut.It was slightly silted up before the 1#rubber dam.(3)According to the study on the operation mode of the new gas shield dam,the hydrodynamic numerical simulation was carried out separately under the condition that the upstream flow rate was 205m~3/s and 2800m~3/s.In the first condition,when the upstream water flow was 205m~3/s,the gas shield dam will store water.After the dam was built,the water level in front of the dam was higher than that before the dam was built,and the flow rate in front of the dam was the opposite.In the second condition,when the upstream water flow was 2800m~3/s,the hydrodynamic characteristics were analyzed before and after the dam construction.At the same time,combining the actual operation of the project,four control schemes were proposed for the dam height of the gas shield dam.The results showed that all sections'water levels were all higher than those before the construction of the dam,except for the downstream outlet,and the flow rates of the sections were all lower than those before the dam construction.Comparing the simulation results of the four schemes,the results showed that the gas shield dam operates best when the dam height is2.5m.(4)According to the best operation mode of gas shield dam collapse and discharge,the sediment mathematical model under the two schemes was constructed.The simulation results showed that after a long period of erosion and siltation,the riverbed scouring and silting basically remained in equilibrium,indicating that the construction of the gas shield dam will not cause much erosion and deposition on the riverbed.