The Morphological Research On Braided Channel Of Yangtze River Source Based On Remote Sensing Image Analysis

The source of the Yangtze River is located on the plateau and is relatively less affected by human activities.The rivers of the Yangtze River Source are still in a state of natural evolution,and they are natural test sites for the study of river evolution.The study on the morphological evolution of the braided river channel of the Yangtze River source is of great significance for improving the understanding of modern river bed evolution and the regularity of sediment movement in plateau rivers under changes in runoff.In this paper,based on remote sensing image analysis,the shape of the braided channel in the source of the Yangtze River is studied.The morphological evolution of braided rivers along the Yangtze River source is studied by analyzing the braided channel morphological parameters such as the braided intensity,the ratio of the water area,the density of the channel,etc.obtained from the processing of Landsat remote sensing image data and comparing different temporal and spatial scale remote sensing images.The main research results are as follows:The main parameter for characterizing the braided channel of the Yangtze River source is the braided intensity index.The comparison of the four braided intensity indices shows that PT and BIT have the best characterization,and the BIT calculation is the simplest to become the most suitable braided intensity index;The intensity is mainly affected by the width and flow of the river,which are the linear relationship and the exponential relationship of the approximate straight line respectively.On this basis,the response patterns of the braided channel to the flow and other factors are analyzed;The interior of the braided river cluster in the source of the Yangtze River has similarities such as the channel density RR of the river channels is close to 0.004/m in the flood season,and differences in channel sinuosity Sc,stability of channel,icing period,etc.Through the study of the properties of braided river channels and remote sensing images of different space-time scales,the evolutionary characteristics and pattern of erosion and deposition of braided rivers are studied:The riverbed of the Yangtze River source braided river has not changed from 1990 to 2016,and the river type has been a braided channel;In the braided river,the change of the channel is mainly through the rush out of the new channel and silt the old channel during the flood season,instead of the slow horizontal scouring of the ramp.The sandbar often produces great differences before and after the flood season;The main channels frequently change,but they mainly switch between several more stable channel channels;Only a small part of the channels is stable for a long time,mostly at the riverbed boundary,and other channels are constantly changing.These stable channels and narrow riverbeds are all nodes that affect the stability of nearby tunnels,limiting the swing of the channel.