Response Of Jingjiang Hydrodynamic Characteristics To Riverbed Erosion Under Typical Water Flow Conditions After The Application Of The Three Gorges Project

After the application of the Three Gorges Project,the riverbed was cut and coarsened in the Jingjiang River downstream of the dam.Based on the topographical and hydrological data in recent years,this paper establishes a three-dimensional mathematical model of the Jingjiang River to study the response of the hydrodynamic characteristics of the Jingjiang River to the undercutting and coarsening of the riverbed.The main research contents and conclusions are as follows:(1)The Jingjiang River of the Yidu~Luoshan section with a length of about 375 km is selected as the calculation area,and the unstructured grid optimized by the beach trough is used to construct a three-dimensional water flow model.The obtained computational grid contains 86,891 computational units(vertically divided into 10 layers)on the plane.The calculated terrain of the model can truly reflect the complex section morphology and complex river conditions of the Yidu~Luoshan section.(2)On the measured terrain of 5 years in 2002,2006,2008,2011 and 2013,the hydrological data(water flow conditions close to the flat beach flow)matched with the year were selected,and the river bed resistance coefficient under each riverbed condition was Cd)The rate is determined.After double comparison of water level and flow rate,repeated debugging,it is obtained that under the above five-year topographic conditions,the distribution of Cd value of Jingjiang main stream(from upstream to downstream)is 0.008-0.002,0.011~0.002,0.013~0.002,0.013~ 0.003,0.013~0.003.Thus,it reveals the response law of the riverbed erosion resistance of the Three Gorges Reservoir during the 10-year period.The annual variation of the cross-section area and trough storage of the river channel below the Jingjiang Pingtan water level in the Three Gorges Reservoir during the past 10 years is analyzed.The overflow area and the trough capacity of the Jingjiang River are increasing year by year,and its overcurrent capacity is increasing year by year.(3)Under the two flow conditions of Pingtan flow and multi-year average flow,the water flow simulation of three working conditions was carried out to study the variation law of Jingjiang hydraulic factors(water level,flow velocity,circulation intensity,etc.)under typical water flow conditions after the Three Gorges Project was applied..The total of 15 sets of three working conditions are as follows: working condition 1,based on the topography of 2002,using the Cd values of 2002,2006,2008,2011 and 2013 respectively;working condition 2,based on the 2002 Cd value,using 2002,2006,2008,2011 and 2013 respectively.The topography of the year;the third condition,using the topography of each year and the corresponding Cd value.(4)The results of the study quantitatively show the response of the river hydraulic factors to the riverbed undercut,the response to the riverbed coarsening,and the response to the riverbed undercutting and coarsening,and the flow velocity of each section is generally decreasing year by year.The form of the riverbed gradually develops into a narrow and deep form;the response curve of the circulation intensity along the curve of the river bed is not obvious;the change law of the hydrodynamic characteristics of the Jingjiang River under the conditions of riverbed undercutting and coarsening is clarified.