Future Urban Expansion Simulation and Flood Mitigation Assessment in the Pearl River Delta under Flood Risk Avoidance

Abstract

Combined with flood risk avoidance-oriented urban expansion strategies, future urban expansion spatial patterns were simulated under Shared Socioeconomic Pathways (SSPs) and Representative Concentration Pathways (RCPs) scenarios. This study compared urban expansion and expected annual damage to evaluate the flood mitigation effects of different strategies. The results show many newly expanded urban lands in the Pearl River Delta are located in floodplains, and the expected annual damage caused by floods is enormous. The most serious economic losses caused by floods were concentrated in southern Guangzhou, eastern Foshan, northern Zhongshan, and northwestern Dongguan. Under the SSP5-RCP8.5-natural expansion scenario, the newly expanded urban lands in floodplains of the Pearl River Delta in 2080 will be 1,633 square kilometers (equivalent to the built-up areas of Guangzhou, Foshan, and Zhongshan combined in 2021), accounting for 31.5% of the total newly expanded urban lands; the expected annual damage will be 2,341.3 billion yuan. If humans manage to reduce emissions in the SSP2-RCP4.5-natural expansion scenario, newly expanded urban lands located in floodplains can decrease to 1,059 square kilometers (-35.1%), accounting for 29.8 % of the total newly expanded urban lands, and the expected annual damage can be reduced to 1,416.5 billion yuan (-39.5%). If flood risk avoidance strategies are included in the urban expansion to optimize and control the spatial pattern of urban expansion, the direction of future urban expansion can change and steer away from areas with high flood risk and toward areas with low or no flood risk. Under the SSP5-RCP8.5-flood risk avoidance scenario, newly expanded urban lands located in floodplains can decrease to 1,358 square kilometers (-16.8%), accounting for 26.2 % of the total newly expanded urban lands, and the expected annual damage can be reduced to 2,001.0 billion yuan (-14.5%). According to the assessment results, emission reduction, and flood risk avoidance strategies can effectively reduce future flood risks. This study improves our understanding of flood risks under different future scenarios, provides a practical reference for developing flood mitigation and urban planning policies in the Pearl River Delta, and motivates decision-makers to formulate corresponding strategies early and effectively to mitigate future flood risks.

Keywords

• urban expansion
• flood risk assessment and mitigation
• future land use simulation
• pearl river delta