Sub-theme
3. Building Resilience for Disaster Prevention and Mitigation
Topic
3-1. Prevention and mitigation of extreme weather induced water-related disasters
Body
With a growing number of waterlogging events occurring in large cities, a better understanding and prediction of the urban flooding processes is essential in order to reduce their impacts. As the capital city of China, Beijing has experienced rapid urbanization process over the past 40 years. Although a large scale drainage system was constructed in the city area, urban waterlogging induced problems frequently occured in Beijing, particularly in heavy storm events. The authorities are keen to find out the underlying causes of waterlogging. In this study, we aim to quantify the waterlogging problems in the urban area of Beijing. A two dimensional hydrodynamic model was used to simulate a surface water flooding process due to a heavy rainstorm event in the urban area of Beijing. Bed topography is a critical factor in hydrodynamic simulation of urban waterlogging, thus an enhanced Digital Elevation Model (DEM) through incorporating road networks over the large areawas presented to describe overland flow through surface pathways and waterlogging forming along the main roads. In order to obtain more accurate information of road elevation, a detailed survey of the major roads of Beijing was undertaken. Rainfall data obtained from a large number of rain gauge stations in Beijing City throughout the whole storm event were acquired. To obtain an overview of the storm-induced overland flows over the urban area, the drainage conveyance and infiltration processes were represented by a simplified manner. The model was capable of reproducing the hydrodynamic process at the city-scale and it was found that surface runoff generated quickly from the surrounding community areas to roads, and accumulated in depression areas. Waterlogging sites reported in the media were extracted, with most of the sites being on roads and predicted reasonably. Rainwater moving through the surrounding community areas and roads contributed predominantly to the formation of waterlogging, while rainwater gathering from over 2 km distance was limited.