Modeling the influence of urbanization on urban pluvial flooding: a scenario-based case study in Shanghai, China

Rapid urbanization has brought great productivity, prosperity and challenges to Shanghai in the last few decades. This paper focuses on the influence of urbanization on urban pluvial flooding, which frequently occurs and causes severe losses, especially in the central urban areas. We quantitatively evaluate the flood risk using scenario simulation methods. The involved scenarios were designed by incorporating two environmental variables (land subsidence and land use/land cover (LULC) change), three time points (2000, 2006 and 2012) and four degrees of rainfall magnitude, with 5-, 10-, 50- and 100-year return periods, respectively. A toolset was developed to model the hydrodynamic process of pluvial flooding in each scenario. The inundation area and average depth were selected as metrics to estimate the severity of flooding, and the corresponding F statistic and root-mean-square deviation were employed to quantify the inundation changes with the impact of all variables. Results suggest that the impacts of land subsidence and LULC change are a function of rainfall magnitude and display a spatial disparity across the entire study area. LULC change is the key factor contributing to the flood risk, which largely affects the inundation extent at a regional scale. Nonetheless, the effects of different land use types are distinctive. The inundation intensifies within industry and transportation land uses and alleviates within green space and waters. Furthermore, except for a slight change captured in the local water depth, the overall flood risk is less sensitive to the impact of land subsidence with varying rainfall magnitudes when compared to the LULC change.