Flash Floods Exposure Assessment Model for DRR Oriented Adaptive Planning in High-density Urban Areas

Rapid urbanization in China is placing increased pressure on urban drainage infrastructure. Northeast coastal cities are susceptible to flood damage from typhoons and climate change is expected to produce more extreme weather events. Urban planners and local governments need better risk assessment tools to plan for future extreme events. An open data based exposure assessment model has been developed for disaster risk reduction (DRR) oriented adaptive urban plan making based on the understanding of flash floods risk in high-density urban areas under future climate scenarios. The proposed model is based on hydrological simulation, which accuracy is sensitive to the precision of input digital elevation model (DEM). A regression kriging based geo-interpolation method is employed to reshape ground surface by increasing precision of global coverage ASTER GDEM from 30m to 10m. Time component is introduced to the Horton’s water permeation model. The parameter of permeation speed limitation is critical to this model; initial values are taken from published Land Classification Codes and adjusted according to the field surveys and observation records. Shekou community in Shenzhen is a case study to verify the proposed model. Two most common scenarios are tested. One is a storm at low-tide condition, with a fully functional urban drainage system. This scenario is simulated by using historical rainfall data from Meteorological Bureau. The other scenario is a typhoon occurring at high-tide, which means urban drainage system is partially malfunctioned. The simulation results show high agreement with both the historical record and satellite observations. Based on the understanding of flash floods exposure assessment and the temporal-spatial distribution of the risk, DRR oriented adaptive urban plans can be made.