Analysis On The Impact Of Coastal Floods,spatial Optimization And Coping Strategies In The Guangzhou Estuary Area

Preparing cities for sea-level rise is one of the most critical issues facing urban communities in the twenty-first century.In particular,weather hazards,and the failure of climate mitigation and adaptation pose substantial risks.These risks are especially significant in fast-urbanizing deltas,such as the Pearl River Delta in China,as the conflict between urbanization and flooding caused by climate change will be more significant in the future.Therefore,identifying the location of future coastal flood risks,optimizing the spatial layout of future urbanization,and formulating coastal flood adaptation strategies must be solved to ensure the safe development of the region.In this paper,taking the Guangzhou estuary area as the research object,the future land use change model(FLUS)and non-dominated genetic algorithm with elite strategy(NSGA-II)were adopted to perform future coastal flood inundation analysis and multi-objective space optimization research.The specific research content is described in the following.First,this study describes a 100-year multi-scenario coastal flooding impact analysis method based on the FLUS model in 2030 and 2050.Guangzhou is taken as an example to explore the impact of urbanization in 2030 and 2050 land use changes,as well as the inundation extent caused by environmental changes(sea level rise,storm surge,and land subsidence).The results show that by 2030 and 2050,the flood exposure value of various types of land will show an increasing trend,with the most obvious increases observed in built-up land and agricultural land.Under the low estimation scenario in 2030,the inundated areas of agricultural land and built-up land are 27.28 km~2 and 17.94 km~2,respectively,accounting for approximately 7.92%and 5.21%of the total inundated areas.With urbanization as the main driving factor,under the low estimation scenario,compared with 2015,the submerged area of built-up land in Guangzhou will increase by 1.9 km~2 and 5.9 km~2 in 2030 and 2050,respectively.Due to environmental changes,under the high-estimation scenario,compared with 2015,the submerged area of built-up land in Guangzhou is expected to increase by approximately 24.2km~2 and 26.8 km~2 in 2030 and 2050,respectively.Second,this study proposes a multi-objective NSGA-II spatial optimization method coupled with the Arc GIS and Python platforms.The objective function is constructed under the constraint of compact development and based on the following factors:the safety and sustainable needs of the future development of the Guangzhou Estuary area;the basic principles of high built-up land development probability and low coastal flood exposure;and the ecological value and regional spatial planning goals.The NSGA-II algorithm is used to optimize the space for new built-up land in 2030.The results show that in 2030,compared with the FLUS simulation scenario,the multi-objective NSGA-II spatial optimization scenario greatly improves the comprehensive fitness function value,from 0.618 to 0.771(24.75%).Different scenarios are constructed based on the objective weight and are compared with simulation scenarios based on historical development.The results show that the fitness value of each scenario is improved compared with the FLUS simulation scenario.This proves the effectiveness of the multi-objective NSGA-Ⅱspatial optimization method under different scenarios.Finally,an integrated decision-making process of"Coastal Flood Inundation Identification-Spatial Optimization-Development of Coping Strategies for Coastal Floods"was established.In the management of the remaining coastal flood exposure after spatial optimization,a model of cross-regional assistance and joint governance by a multidisciplinary team of experts was proposed for the engineering of the open estuary scenario.In addition,content such as building and environmental renovation were formulated,and the Resilient Estuary Closure Project was established.Following this,an emergency strategy for non-engineering measures was determined to provide a scientific reference to effectively reduce the risk of coastal flood exposure in the Guangzhou estuary area.