Analysis Of Land Use Pattern And Driving Force Of Wanjiang River Shoreline Based On Remote Sensing

Since the implementation of the "Yangtze River Protection" program,the Wanjiang River shoreline had adopted ’ 1515 ’ hierarchical control measures,with the aim of promoting clean water and greenery along the shoreline in the Wanjiang Economic Belt.In order to assess the effectiveness of the protection measures along the Wanjiang River shoreline and explore the long-term evolution,characteristics,and patterns of land use types in the Wanjiang River Basin,it is essential to provide effective foundation support for the subsequent ecological development of the Wanjiang River Basin.Based on the Google Earth Engine(GEE)platform,this thesis toke the 15 km range on both sides of the Wanjiang River as the research area,and used the Landsat series of remote sensing images from 1989 to 2021 to establish an automatic classification rule for the riverside wetlands,while the remaining land classes were classified by using Random forest classification.Then,the thesis analyzed the area variation characteristics of land cover changes along the Wanjiang River shoreline.In addition,GIS spatial analysis methods were employed to analyze the spatiotemporal pattern changes in land use.Finally,a geodetector was used to investigate the driving mechanisms behind land cover changes.The main conclusions were as follows:(1)The overall accuracy of the automated extraction rules for the riverside wetlands reached 91.0%,with a Kappa coefficient of 0.87,indicating a favorable extraction performance.The Random forest algorithm achieved a consistent classification accuracy for the period of 1989 to 2021,ranging between 96% and 98%.Compared with the time-filtered composite images,the composite images of percentile algorithm had better synthesis effect and relatively high classification accuracy.(2)The overall water area of the Yangtze River in the Anhui section exhibited a downward trend,with a decrease of 57.63 km~2.From 1989 to 2003,the average annual area of tidal flats was relatively high.During this period,the sediment in the water body of Wanjiang River continued to accumulate,leading to the formation of sandbars.After the completion of the Three Gorges Dam on the Yangtze River in 2003,the tidal flats showed a downward trend.Due to the influence of rainfall,the average annual area of the marshland increased to95.1 km~2 from 2016 to 2021.From 1989 to 2021,the area of construction land within a 15 km range exhibited a linear growth,with an average annual increase of 38.01 km~2,while the growth rate of construction land within the dam area decelerated during the period of 2017-2021.On the other hand,the area of forest land within 15 km range began to rise since 1999,while within the dam area,it started to grow after 2013.(3)From 1989 to 2017,land use dynamic degree of construction land was higher,and from 2017 to 2021,the riverside wetland was higher.The land use degree in the dam line is relatively small compared to the 15 km range,and the land use degree in both ranges experienced a decrease in 2017.From 2013 to 2017,there was a phenomenon that construction land reversed to cultivated land;Since 1999,there has been a transition of cropland to forested land,and low-density forested areas started to emerge along both banks of the river after 2013.River lake wetlands had been transferred out to cultivated land and artificial wetlands,with a decreasing trend in conversion area after 2013.(4)The driving forces behind land use changes within a 15 km range along both banks of the Wanjiang River had shifted from topographical factors represented by elevation in 1999 to social and economic factors;Furthermore,during the period of 2017-2021,the influence of economic factors gradually diminished,while the impact of population data steadily increased.The above results indicated that the overall Wanjiang River shoreline is undergoing urbanization,and the areas of forests had an increase due to policy implementation.The results within the dam area suggested that the completion of the Three Gorges Dam on the Yangtze River altered the dynamics of riverside wetlands.Furthermore,measures such as afforestation for protection,renovation of ports and docks,and shoreline greening had also shown initial effectiveness.