Research On The Coastal Erosion Evaluation Of Headland Bay In Wenzhou Area

Coastal zone is an inseparable living area of human beings.Coastal erosion and siltation always exist in the coastal zone system.Due to its unique geomorphologic features,sandy beaches are separated into independent dynamic sedimentary systems by coastal headlands.Under the background of global warming,rising sea level and increasing human activities,coastal erosion disaster in some areas is becoming increasingly prominent.In this paper Nine typical headland and bay-type sandy beaches in Wenzhou area are selected as the main research objects.Firstly,the general situation of the natural environment in Wenzhou was sorted out,and the geographical location information,topography,geomorphic features,climate,meteorological conditions,wind regime,wave characteristics,tides,tidal current and residual current characteristics were collected and summarized in the study area.Secondly,combined with the remote sensing satellite image data,the paper describes and analyzes the overall evolution characteristics of the historical coastline in Wenzhou.Based on a large area of field exploration,a total of forty-seven monitoring sections were set up to collect beach shoreline and fine beach topographic elevation data to study the characteristics of beach interannual erosion and deposition and profile erosion changes.By comparing the relative positions of the simulated shoreline with the actual shoreline in recent years,this paper studies the shoreline advance and retreat trend of the arc-shaped sandy coast of cape bay,and analyzes the beach stability of cape bay coast in Wenzhou area.Finally,six evaluation indexes,including shoreline recede rate,shoreline erosion rate,shoreline slope and relative sea level change,were selected to calculate the weights by a combination of analytic hierarchy process(AHP)and coefficient of variation method,and the evaluation system of coastal erosion in Wenzhou area was constructed to comprehensively evaluate the intensity of coastal erosion.The results show that in recent years,the total length of the coastline of the mainland and islands in Wenzhou has decreased,while the artificial coastline has increased at a faster rate.The parabolic model has a good adaptability to judge the stability of Haiwan beach in Wenzhou,and the coastline in the study area is in a stable state as a whole.According to the beach foreshore monitoring profile data,the sandy beach profile morphology in Wenzhou area can be divided into four types: lower concave type,upper convex type,slope type,and combined slope + upper convex type.The interannual scour and deposition of the profile can be divided into three types,namely up-scour and down-stacking,all-around scour and basically stable scour.The results of coastal erosion evaluation show that the sandy coast of cape bay in wenzhou area is generally stable and slightly eroded.Among them,Changsha Village,Wicheng Ao and Xiwan Golden Beach are judged to be micro-erosion,which need to be monitored particularly.