Study On The Spatial-Temporal Evolution Characteristics And Driving Factors Of The Sandy Coastline In Guangdong Province Based On Landsat Images

Shoreline contains important information associated with coastal processes and climate variation.However,domestic studies on shoreline evolution processes in the medium to long term and its driving mechanism are relatively sparse.Based on large sample data of the Landsat series around 1986-2021 and the 116 control point data collected by the field survey from 2015 to 2019.thesis established coastline interpretation marks to extract the high-water lines(HWL)of 17 beaches in Guangdong Province The accuracy of shoreline extraction was evaluated by Average Root Mean Square Error of point-line distance.On this basis,the End Point Rate(EPR)and Linear Regression Rate(LRR)methods are used to study the long-term variation characteristics of the coastline at the bay scale,and linear methods(EPR and LRR methods)and nonlinear methods(second-order polynomials)are used to evaluate the linear or nonlinear behavior of coastline evolution in different segments of each bay.The Mann-Kendall(M-K)trend test method and Empirical Orthogonal Function(EOF)is introduced to reveal the evolution process of coastline in more detail,focusing on the trend reversal or significant trend Changes,analyze the main controlling factors affecting each bay.The main conclusions of the full text are as follows:(1)In the past 30 years,the erosion rate of beaches was less than 2m/a,and the overall shoreline change was stable in Pinghai Bay,Pinghai East,Houmen West,Yiqi Bay,Hudong Bay,Jiazi West,Jiazi Bay,etc.There were lots of erosion hotspot areas,mainly distributed in the eastern side of Wukan Bay,Jinxiang Town shore section,Sanzhou Bay,the western side of Houpu Village to Xing small and medium school shore section,Jinghai Bay,the western side of Huwei Lian to Jinghai Bay Resort shore section,Haimen South Wushi Chai shore section,Haimen Bay,Tianxin Town shore section,Qiwang Bay and Nanshan shore section.Additionally,there were also numerous siltation hotspot areas,which were mainly located in the shore section from Wutong Village Committee to Shanwei Maritime Bureau on the east side of Shanwei Bay,the shore section of Houjiang Bay Puchashi and the shore section from Taihu Town to Luo River in Wukan Bay.Among the areas including Shenquan Bay mountain front shore section,Jinghai Bay Resort to the eastern side of the bay shore section,Qiwang Bay Zhonghai Resort to Huzai Mountain shore section and Nanshan to Xiyu shore section,were also siltation hot spots.(2)Among the 17 sandy beaches in Guangdong Province,more than 50% of the coastlines of 13 bays show nonlinear change behavior.For the beaches of Shanwei Bay,Wukan Bay,Jiazi Bay,and Haime South,the four coastlines mainly show linear change behavior.(3)The Mann-Kendall trend test and the EOF decomposition method explore the time of significant coastline changes through the significance test and time coefficient respectively,which better solved the problem of lack of basis for the division of the study period in the existing research.(4)Human activities are the main driving mechanism for the evolution of sandy coastlines in Guangdong Province.The influence of sea reclamation,urban expansion,coastal sand mining and coastal engineering has changed the planform of the bay and redistributed the wave dynamics in the bay.The result was that the coastal system adjusted rapidly to adapt to the dynamics,thus changing the process of beach erosion siltation and underwater topographic washout.Finally,the shorelines of them had been changed.There are 33 figures,10 tables and 88 references.