Research On Spatiotemporal Variability Of Urban Water Logging Hazards In The Pearl River Delta Under Changing Environment

Under the backdrop of global climate change and rapid urbanization, urban water logging hazards are aggravating, thretening residents’ lives and property, and thus are drawn much attention by the international community. The Pearl River Delta(PRD) is playing an exemplary role in social economic development in China, however, due to frequent extreme rainfall, storm surge and river flood intrusion, urban flooding often occurs in PRD that has negative impacts on economic development. Exploration of simulation technique of coastal urban flooding in South China would broaden the methodologies of understanding coastal urban flooding, whilst study on spatiotemporal changes in urban water logging hazards in PRD under chaning environment can not only enrich the theories of urban flooding, but also helps for making flood adaptations and defences for PRD. This study built a coupled urban flooding model and took a typical district in Dongguan as an exmple to analyze the spatiotemporal changes in water logging hazards based on scenario simulation. Main conclusions were summarized below.(1) An urban flooding model suitable for coastal regions in South China was proposed. This model was developed through coupling the SWMM model with the LSFLOOD-FP model, which allows data interchange between SWMM and LSFLOOD-FP at each time step. It can synchronously simulate inundated area and depth during a flood event and was proved to have preferable applicability in the study region.(2) For the 1-, 2-, 5-, 10- and 20-year return periods of rainstorm, water logging hazards are the most serious at approximately the time rainfall peaks occur, with maximum inundated depth and area respectively being 0.3~1.8 m and 40 000~90 000 m2. The inundated areas and depths are spatially heterogeneous. Maximum inundated area and depth increase with greater return period; however, the inundated spots and corresponding chaning patterns of water logging hazards are similar.(3) For regions alongside the Dongyin Canal, maximum inundated area and depth would significantly increse after rainfall peak due to 0.2 m or 0.4 m land subsidence/river level rise. By comparsion, land subsidence and river level rise have little impacts on water logging hazards in regions far away from the Dongyin Canal.(4) The extreme environment, a combined scenario of 100 a return period of rainstorm, 0.5 m land subsidence and 0.7 m river level rise, would lead to aggravated and severe water logging hazards in the study region. Maximum inundated area and depth would significantly increase with values respectively exceeding 120 000 m2 and up to 2.6 m.(5) Adopting permeable pavements and green roofs to the study region, as the results show, can effectively alleviate water logging hazards.