中国沿海地区的洪水风险与适应路径研究

【作者】 王丹；

【导师】 杜士强；

【作者基本信息】 上海师范大学 ， 自然地理学， 2022， 硕士

【摘要】 随着全球气候变化与快速城市化,海岸洪水风险正在不断加剧。科学认识未来海岸洪水风险变化规律并进行有效适应,可以帮助缓解风险,保障可持续发展。中国海岸线漫长,沿海地区社会经济集聚且发展迅速,易受海岸洪水的影响,亟需进行洪水风险评估,并对相应的沿海适应路径展开经济可行性分析。然而,目前尚没有研究聚焦中国沿海地区,探索其海岸洪水时空变化规律,分析其适应路径的经济效益及城乡差异。为弥补这一研究空白,本文收集多源防洪标准数据,构建了中国县级海岸洪水防洪标准数据集;采用最新极端海平面数据、沿海高程数据等基础数据,使用水文-水动力学模拟与情景分析等方法,模拟了多重现期下海岸洪水的空间分布及未来变化;基于土地利用数据、资产价值分布数据、深度损失率曲线等基础数据,综合运用风险分析、成本收益分析和差异性分析等方法,研究了海岸洪水风险的空间格局、未来变化及城乡差异,探索了“维持当前设防水平”的适应路径(根据海平面上升等情况维护、升级现有适应措施,使设防等级维持在当前水平)在空间上的经济效益及城乡差异。主要研究结论如下:(1)揭示了9个重现期下海岸洪水淹没的空间分布及未来变化规律。随着洪水重现期的逐步增加,即从2年一遇洪水变化为1000年一遇洪水的过程中,海岸洪水的淹没范围不断扩大,淹没深度不断增加。不考虑现有的沿海适应措施,1000年一遇洪水将淹没5.3%(7.1万km(?))的沿海地区;若不采用一定的沿海适应路径,到2100年该淹没比例即使在RCP4.5情景下也将增加至6.0%–6.8%。在空间上,各重现期洪水集中分布在长江三角洲、珠江三角洲,以及环渤海地区。(2)构建了最新的中国县级海岸洪水防洪标准数据集,评估分析了县级尺度上的海岸洪水风险时空格局。27.6%(197个)的县级行政单位受到了海岸洪水的影响。与不考虑设防水平相比,考虑设防水平使得风险显著下降,年期望损失从6471.9亿元下降为189.0亿元,降幅达97.1%。在空间上,风险明显下降的县级行政单位集中于环渤海地区、长江三角洲和珠江三角洲等社会经济相对发达的城市地区。若不对现有的适应措施进行维护或提升,未来风险将呈现快速增加趋势。RCP8.5 High-end_SSP5情景下,年均增长率可达4.2%(3.9%–4.8%)。因此,有必要采取一定的沿海适应路径,缓解不断增长的风险。(3)量化了不同未来情景下“维持当前设防水平”这一沿海适应路径的经济效益。首先,社会经济的发展和温室气体的排放量影响着各县级行政单位的经济效益。不同未来气候变化情景之下,具有经济效益的县级行政单位数量在107至137之间浮动。随着社会经济的加速发展和温室气体的增加,该数量呈增加趋势。其次,具有经济效益的县级行政单位数量随着折现率的降低而增加。因此,需密切关注未来气候变化和社会经济发展,不断评估未来投资的经济回报,做出适时调控,以增加经济效益。(4)揭示了上述适应路径在64.0%的县级行政单位具有经济鲁棒性。综合所有情景下的54种成本收益分析结果,采用“维持当前设防水平”的沿海适应路径在105个(64.0%)县级行政单位具有经济鲁棒性,即所有情景下的减灾收益均大于减灾成本;分布于河北省、天津市、江苏省、上海市、浙江省和广东省。剩下的58个不具经济鲁棒性的县级行政单位中,有22个在任何一种情景下都不具有经济效益,分布于辽宁省、山东省、福建省和广东省。针对这58个县级行政单位,需根据地区特征,采用更适合的沿海适应路径,或增添补充性适应措施,或加入基于自然的解决方案,构成混合型适应措施。可靠的信息收集与完善的分析技术有助于降低成本收益分析结果的不确定性。(5)探索了海岸洪水风险和上述适应路径经济效益的城乡差异。结果表明:城乡海岸洪水风险无显著差异,但城市绝对风险较高,农村相对风险较高。采用“维持当前设防水平”的适应路径,城乡间并没有显著的经济效益差异。据此,关注城市洪水风险的同时,应当同等关注农村洪水风险,重点降低农村地区的洪水损失率,并关注城市地区的剩余风险问题。此外,针对资产相对密集的城市地区,应合理规划人口布局,优化城市发展方向;针对资产相对稀疏的农村地区,需重点补充非工程性防洪措施,提升少数社会脆弱人口的洪水适应能力。基于自然的解决方案可在一定程度上有效服务于沿海地区。本文聚焦中国沿海地区,综合使用水文-水动力学模拟、洪水风险分析、情景分析、成本收益分析和差异性分析,对中国海岸洪水风险及适应路径的经济效益展开空间分析和差异性分析,以探索中国沿海地区如何经济有效地防范洪水,同时针对城市地区和农村地区提出了沿海适应路径建议,具有一定的创新性和现实意义。相关结论可以为沿海地区制定减灾策略、减少地区差异、实现可持续发展提供一定的科学依据。更多还原

【Abstract】 With global climate change and rapid urbanization,coastal areas are facing increasing flood risk.Scientific understanding of the future coastal flood risk changes and effective adaptation can help mitigate risk and ensure sustainable development.China has a long coastline,and its coastal areas are vulnerable to coastal flooding due to rapid socioeconomic agglomeration and development.There is an urgent need for flood risk assessment and economic feasibility analysis of corresponding coastal adaptation pathways.However,there is no research exploring the spatial and temporal patterns of coastal flooding and analyzing the economic efficiency of adaptation pathways and their urban-rural differences in coastal areas of China at the national scale.To fill this gap,multi-source flood control standards were collected to develop the latest county-level coastal flood control standard dataset.Based on the latest extreme sea level data,coastal elevation data and other basic data,hydrological-hydrodynamic simulation and scenario analysis were used to simulate the spatial distribution and future changes of coastal flooding under multiple return periods.Based on land use data,asset value data,vulnerability curve and other basic data,methods such as risk analysis,costbenefit analysis and variance analysis were used to analyze the spatial pattern,future changes and urban-rural differences of coastal flood risk,and further explore the spatial economic efficiency and urban-rural differences of the adaptation pathway of“maintaining the current flood protection level”(maintaining and upgrading the existing adaptation measures to maintain the current flood protection level according to sea level rise).As follows are the main conclusions:1.The spatial distribution and future changes of coastal flooding under 9 return periods was revealed.With the increase of the flood return period,that is,from a 2-year to 1000-year return period,the inundation area of coastal flooding is expanding and the inundation depth is increasing.Without considering the existing coastal flood protection measures,the flood of a 1000-year return period will inundate 5.3%(71,000km(?))of the coastal areas.And without adopting certain adaptation pathways,this inundation proportion will increase to 6.0–6.8% in 2100 along with future sea level rise of the RCP4.5 scenario.Spatially,the floods of each return period are concentrated in the coastal zones of the Bohai Rim,Yangtze River Delta and Pearl River Delta.2.An updated dataset of county-level coastal flood protection standard in China was constructed and the spatial and temporal patterns of coastal flood risk at the countylevel scale in China were evaluated.27.6%(197)of county-level administrative units were affected by coastal flooding.Considering the flood protection level led to a significant reduction in coastal flood risk compared to not considering the flood protection level,with annual expected damage decreasing from 647.19 billion yuan to18.90 billion yuan,or 97.1%.Spatially,the administrative units with significantly reduced risk are concentrated in the more socio-economically developed urban areas such as the Bohai Rim,Yangtze River Delta and Pearl River Delta.If the existing adaptation measures are not maintained or upgraded,future coastal flood risk will increase rapidly.Under the extreme scenario of RCP8.5 High-end_SSP5,the average annual growth rate can reach 4.2(3.9–4.8)%.Therefore,certain coastal adaptation pathways are necessary to mitigate increasing flood risk.3.The economic efficiency of the coastal adaptation pathway of “maintaining the current flood protection level” under different future scenarios are quantified.First,socioeconomic development and GHG emissions affect the economic efficiency of each county administrative unit.Under different future scenarios,the number of administrative units with NPV>0(or BCR>1)fluctuates between 107 and 137.The number tends to increase with accelerated socioeconomic development and increasing GHG concentrations.Second,the number of administrative units with economic efficiency increases as the discount rate decreases.Therefore,it is necessary to pay attention to future climate change and socio-economic development,continuously assess the economic return of future investments,and make timely adjustments to increase economic efficiency.4.It revealed that the above adaptation pathway is economically robust in 64.0%of the county-level administrative units.Combining the results of 54 cost-benefit analyses under all scenarios,the coastal adaptation pathway of “maintaining the current flood protection level” is economically robust in 105 county-level administrative units(64.0%),i.e.,the benefits of disaster reduction under all scenarios are greater than the costs of disaster reduction;they are widely distributed in the province of Hebei,Tianjin,Jiangsu,Shanghai,Zhejiang,and Guangdong.Shanghai,Zhejiang,and Guangdong.For the remaining 58 county-level administrative units that are not economically robust,22 of them do not have economic efficiency under any of the scenarios,and they are located in the province of Liaoning,Shandong,Fujian,and Guangdong.For these 58 administrative units that are not economically robust,it is necessary to adopt more suitable coastal adaptation pathways based on regional characteristics,either by adding complementary adaptation measures or by incorporating nature-based solutions to constitute hybrid adaptation measures.Reliable information collection and sound analysis techniques can help reduce the uncertainty of cost-benefit analysis.5.The urban-rural differences in coastal flood risk and the economic efficiency of the above adaptation pathway were explored.In terms of coastal flood risk,there is no significant difference between urban and rural areas;however,the absolute risk is higher in urban areas and the relative risk is higher in rural areas.There is also no significant difference in economic efficiency between urban and rural areas using the adaptation pathway of “maintaining the current flood protection level”.Accordingly,while paying attention to urban flood risk,equal attention should be paid to rural flood risk: in rural areas reducing the flood loss rate should be focused and in urban areas the residual risk should be paid attention.Meanwhile,urban areas and rural areas should also be optimized equally: for urban areas with relatively dense assets,the population layout should be reasonably planned to optimize the urban development direction;for rural areas with relatively sparse assets,the focus should be on supplementing nonengineered flood protection measures to improve the ability to adapt floods of a small socially vulnerable population.In addition,nature-based solutions can effectively serve coastal areas to a certain extent.Taking the coastal areas of China as the study area,the paper uses hydrologicalhydrodynamic simulation,flood risk analysis,scenario analysis,cost-benefit analysis and variability analysis to conduct spatial analysis and variability analysis on the economic efficiency of coastal flood risks and adaptation pathways,in order to explore how to prevent floods economically and effectively,and also proposes corresponding coastal adaptation for urban and rural areas,which are innovative and practical.The findings can provide a scientific basis for coastal areas to formulate disaster mitigation strategies,reduce regional differences,and achieve sustainable development.更多还原