Study On Risk Assessment Modeling Of Coastal Erosion And Its Application

Under the guidance of marine geosciences theory and disaster economics theory,analytic hierarchy process, fuzzy set theory and geographic information technologywere employed to study on coastal erosion risk assessment modeling based on fieldstudy, literature research and expert consultation.Conclusions, as follows, were drawn both on the combination of qualitativeanalysis and quantitative calculation,and theory and practice:(1) Establish the risk assessment system of coastal erosion for China coastalmanagement. Thirteen indacators are selected, basing on natural and socialcharacteristics to assess coastal erosion risk: erodibility, shoreline evolution, waveheight, relative sea-level rise, coastal urbanization rate, storm surge, tidal range,population density, gross domestic products (GDP), sea area class, budgetary revenueof local government (BRLG), coastal protection capacity and land use/cover change(LUCC).(2) Weight the indicators and select membership function. The five indicatorsrelated tostructural erosion of which erodibility gets the final weight of0.5065,themost important one; with shoreline evolution asrunner-up; wave height, relativesea-level rise andcoastal urbanization ranked third, fourth and fifth successively. Theforemost indicator of acuteerosion was also erodibilitywith the weight of0.6845,whichmeans storm surge and tidal range contributed less than40%toacute erosion,and storm surge was of much more importance thantidal range. Population densitytook importance of more than60%among the three indicators related to exposureextent, sea areaclass and GDP level was second and third priority. Deficiencyincoping capacity includesdeficiencies in budgetary revenue of localgovernment,coastal protection and land preservation of whichcoastal protection deficiency was farmore significant than theothers; budgetary revenue and land preservation werealmostequal to each other with the BRLG preceding slightly.Normal membershipfunction is used for risk classification.(3) The case study of Fujian province demonstrated that the resultsof integrated riskassessment of coastal erosion based on fuzzy settheory is effectively supported by thedata and provides lots of important information for coastal management. The top five regionsof integrated risk level that need urgent mitigation measuresfor coastal erosionwere Jinjiang, Shishi, Xiamen, Changle andNanan that complied with the top regionsof erodibility, shorelineevolution, storm surge, population density, deficiency incoastalprotection, sea area class and budgetary revenue of local government,whichmeans that the integrated risk levels of Fujian coastwere in line with the field study.(4)Sandy coastal erosion, soft rock coastal erosion, muddy coastal erosion,biological coastal erosion and coastal structural erosion are identified according to thecharacteristics of erosion in China. Beach engineering such as beach nourishment ismore important for sandy coastal erosion, coast engineering could use as supplement;however, for muddy coastal erosion coast engineering is the first thing to do, beachengineering is secondary; adaptive measures are usually adopted for biological coastalerosion, for example, the reserves and setback zones; coastal structural erosionhappens downstream along coastal engineering, which may appears for years after theengineering, the most effective measure is to stop unreasonable construction alongerodible coast.