Morphological Change Of Lancang River From Jinghong To Guanlei Reach Based On Multi-Resolution RS Imagery

River bed evolution is an important part of river geomorphology research and has attracted extensive attention from scholars at home and abroad.The change of river form is the result of long-term interaction between the sediment flow and the riverbed material.With the increase of human activities,it will affect the process of riverbed morphological changes to a certain extent.The Lancang-Mekong River is an important international river in Asia.And the Lancang River in Yunnan Province is an important hydropower energy base in China.The downstream area is a typical mountain river.The valley is characterized by the middle and low mountains and wide valleys.Since the 1990s,large-scale cascade hydropower development in the middle and lower reaches of the Lancang River has undergone significant changes in the downstream water and sand.In addition,the impact of downstream human activities has increased,has it caused river morphology change in the lower reaches of Lancang River?What changes have taken place?What are the influencing factors of change?It is urgent to carry out relevant research to explore.In view of this,this study selected Jinghong to Guanlei reach of Lancang River based on long-time multi-spatial resolution remote sensing imagery,Comparing and Selecting Interpretation Methods of River Water in Mountainous Areas.On this basis.the spatial and temporal variation characteristics of the rivers in the lower reaches of the Lancang River are analysed from the regional and typical river sections.Based on field verification,field interviews and laboratory tests,the influencing factors of river morphology change in the lower reaches of Lancang River are discussed.The main conclusions are as follows:(1)By comparing and analysing the application of single-band threshold method,water index method and supervised classification method in water body interpretation of mountain rivers,the supervised classification method has relatively good interpretation effect.The river morphology of the of Lancang River extracted by this method has clear outline and high quality.This method is more suitable for extracting the shape of a river of mountain rivers with large topographic fluctuations and shadows.(2)Based on the Landsat imagery,we analysed the river morphology from Jinghong to the Guanlei section of the Lancang River.It was found that the river morpholog had no significant change except for the wide valley section,However,the instantaneous surface area and average width both have increased to some extent.The coastline along the river section showed an overall growth trend from 1993 to 2017.rThe left bank line was longer than the right bank,but the average rate of change andthe average speed of change were lower than the right bank.In the change of erosion and siltation,the erosion area of Jinghong to Guanlei section of Lancang River was larger than that of siltation area in 1993-2017.And the changes of river morphology were most obvious in Jinghongba and Ganlanba wide valleys.(3)In general,the erosion area are larser than the siltation area in the Ganlanba and Jinghongba.Among them,the instantaneous water surface area and the area of central bar of Jinghongba decreased from 2006 to 2015,but the area of the beach increased.The river channel is dominated by erosion,and the erosion area is 0.36km2.The erosion on the right bank is more obvious than that on the left bank.The erosion from the Yunjinghong station to the Jinghong old bridge is obvious.The channel erosion in the center of the village is also developed.In the Ganlanba section,the instantaneous water surface area and the beach area increased in 2003-2016.and the area of central bar decreased.Especially in the Xishuangbanna Dai Garden.Manau,Manlong and other areas have changed significantly.From the perspective of river channel erosion and erosion,the area of the river section was 0.31km2 and the sedimentation area was 0.1]km2 in 2003-2016.The right bank of the Ganlanba is dominated by erosion.,while the left bank is dominated by siltation.(4)The morphological changes of Jinghong to the Guanlei section of the Lancang River are mainly affected by factors such as cascade hydropower development,River reconstruction and river sand mining.Cascade hydropower development has significantly changed the relationship between downstream water and sand,mainly due to the reduction of flood water level and the reduction of sediment deposition in the wide valley section;river reconstruction has significantly reduced the flood level of the Ganlanba section;in the case of reduced sand in the upper reaches,large-scale river sand mining accelerates the morphological changes of rivers in typical river sections.The study has certain reference value for clarifying the morphological characteristics of rivers and river sediment management in mountainous areas under strong human disturbance.