Characteristics Of Bars And Channels In Braided River Of The Yangtze River Source And Simulation Research Based On Machine Learning

Braided rivers are widely developed in the Yangtze River Source.Different sizes of sand bars,side bars and central bars are extensively developed in different geometric scales of braided rivers.The overall morphology of the river is irregular,and many channels between the bars are randomly interlaced.The erosion and deposition in the braided channels are intense.The study on the characteristics of the braided river’s bars and channels is helpful to further understand the braided river characteristics and the plateau sediment transport law under the action of runoff.Based on Landsat series remote sensing images,this essay analyzes the change process of bars and channels in braided river by introducing the morphological parameters and combining with runoff.Finally,based on machine learning algorithm,the evolution process of the channels is simulated,then,the corresponding channel distribution characteristics is presented under the guidance of input runoff value.The main results are as follows:Side bars in braided river of the Yangtze River Source can be divided into stable,sub-stable and active side bars.Factors affecting the change of active side bars include runoff and duration of high-level water flow.The sharp decrease of the side bar is due to the formation of new branch channels on the side bars during flood period.The scouring and eroding of the flow along the new channels urges the original side bars to separate into new side bars and new central bars.With the water level dropping and depositing,the combination of central bars and side bars resulting in drastic changes in the side bars during dry season.The irregular shape of group bars in braided rivers is caused by the eroding of water flow.The main mechanism of group bars eroding is the water level difference between adjacent channels,which makes surface easily scour and erode to form new channels after the water overflows the bars.The number of channels in braided river increases and decreases rapidly.For the flat valley of braided rivers,the river width has no restriction on the development of channels,It can also develop into multiple channels and prestent the planar feature of parallel multiple branches in the areas with smaller width.There is a critical value for the braided index NL of different river widths with the increase of runoff.When the flow is extremely large,the overbank flow and the movement of the bars will lead to the confluence,the braided index will decrease instead.During the flood,the main channel translocates when the flow rate of the main channel decreases continuously.Compared with large-scale floods,medium-scale and small-scale floods have stronger ability to reshape riverbed morphology.Finally,the braided channel generation model established by combining the runoff value with the DCGAN machine learning algorithm.After the runoff value as label is input to the generation model,the generated braided channels image has similar characteristics with the real remote sensing image,Therefore,the model can be used to simulate the distribution and evolution characteristics of the braided channels under the effect of runoff.