Author(s): Husnain Tansar; Zhi-Yong Long; Huan-Feng Duan
Linked Author(s): Huan-Feng Duan
Keywords: Urban flooding; Rainstorm; Storm surge; Compound flooding; Drainage system
Abstract: Coastal cities have become highly vulnerable to pluvial flooding because of compound effect of intense rainfall and storm surge events with rapidly changing climate conditions. In late 2023, Hong Kong witnessed three major rainstorm events with higher return periods (i. e., 100 ‒ 500 years), causing severe socio-economic damages to the local government and public properties. Urban flood modeling at a finer scale (i. e., 1 meter or less) of highly densely populated coastal regions with complex infrastructure systems and topography is one of the biggest challenges, because of limited availability of information on underground drainage systems and computational costs. A coupled modeling package of stormwater management model (SWMM) and LISFLOOD-FP is employed for modeling of 1D underground urban drainage system and 2D overland flooding of Heng Fa Chuen, Chai Wan and Siu Sai Wan regions, a low-lying case study of Hong Kong. The integrated modeling framework was calibrated based on reported and observed flood depth and extent measurements. The flood hazard of the region is evaluated under different rainstorm and storm surge scenarios under compound conditions, and further investigation was made based on delineated flood zones. Results of the case study concluded that the rainstorm-based floods severely impacted roads and various building types compared to mountainous regions. Furthermore, coastal infrastructure and residential buildings located neighboring to the shoreline are highly impacted by storm surge-induced flooding. The capacity of existing urban drainage system and shoreline protection infrastructure need to be upgraded as potential mitigation measures to avoid future disruption in transportation systems, and the potential reduction of future compound flood risks to local residents and their properties.
Year: 2024