| Fuhe and Qinglan Lake are located in the eastern part of Jiangxi Province,both belong to Poyang Lake Basin.Since the implementation of the Fuhe diversion project,the river-lake relationship of Qinglan Lake has undergone a fundamental change.A typical widening river channel will be formed into the downstream of the diversion road.Changes in the water and sediment conditions of Qinglan Lake will lead to sedimentation in the Qinglan Lake and change the shape of Qinglan Lake.According to the results of river engineering model test,levee type deposition,point dam,longitudinal dam and other deposition forms are easy to occur during the adjustment along the river course,as well as the phenomenon of cutting bank and river course oscillation.This paper mainly uses numerical simulation to simulate the phenomena that may occur during the sedimentation adjustment process in the Qinglan Lake area.The conclusions follow as:Firstly,this paper establishes a two-dimensional mathematical model of water flow basing on Mike software;At the same time,the water level and section velocity distribution of the model are verified according to the measured hydrological data.Secondly,the two-dimensional flow numerical model is used to simulate the water flow conditions in the study area before and after the implementation of the diversion project.Finally,the two-dimensional flow numerical model is used to couple the sediment module,based on the long series of annual water and sediment conditions and typical working conditions,the sediment deposition in the Qinglan Lake area after the diversion project is simulated and the sedimentation is developed,and the process and changes in water flow conditions before and after siltation are analyzed.The conclusions follow as:(1)The model has a high simulation approximation,which can simulate the water flow and sedimentation process in the study area.(2)The water level in the Fuhe section of the upper has reduced to different degrees,while the water level in the Qinglan Lake area is still high.The upstream velocity and the re-route section is increased,which is greater than that in the lower section.Under the condition of river flooding,the water level and velocity of the study area change significantly.Meanwhile,the variation of water level and flow rate under flood condition is consistent with the river flood condition,and the amplitude of variation is reduced.(3)The sedimentation development process in the Qinglan Lake area was mainly from top to bottom.In the process of neck siltation,the channel of Qinglan Lake was single,and the abdominal siltation of Qinglan Lake was complicated,with bifurcation and channel oscillation.After the siltation,the elevation was basically the same as that of the water level.The water level in the Qinglan Lake area rose as a whole,and the ratio was slightly increased.The flow velocity in the lake area was increased by the narrowing of the river bed.In addition,during the sedimentation process,the occurrence of the heart-sand has caused the resistance distribution of the river section unevenly.The water level of the river channel in the upper reaches of the heart of the river was continuously rising.The gradient ratio was reduced.The hammed water phenomenon was occurred.The flow rate was continuously reduced,which caused the river channel to divert to both sides of the heart beach.It is found that the sedimentation development process in Qinglan Lake area is basically the same according to the comparison between the results of numerical simulation and the results of river model test.The neck channel of Qinglan Lake is single.And the abdomen shows the phenomenon of bifiurcation and river regime variation,which indicates that Mike software can approximately simulate the phenomenon of bifurcation and river regime variation and etc.in the sedimentation adjustment in the river channel. |
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