Coupling 1D-2D hydrodynamic model for urban flooding simulation based on multi-faceted data in Hong Kong

Abstract Flooding has intensified due to climate change and rapid urbanisation. Extensive studies have been conducted to simulate flooding of outdoor environment. However, limited studies have been conducted inintegrating outdoor and indoor flooding risk assessment. Therefore, this study adopted Infowork ICM model and integrated multi-facted data, including open-sourced drainage networks, 3D visualisation maps, territory habitat maps, raingauge data and minute-interval Kai Tak river level data from monitoring stations provided by the Drainage Service Department to examine and identify risky outdoor and indoor areas under extreme rainfall based on simulated scenarios. The study area is the part of the Kowloon East Area. Specifically, two rainfall scenarios, with different return periods and durations (the index quantifying the severity of rainfall), have been designed and analysed. The RMSE is 45 mm. The simulated result reveals that 15.0%, 25.1% and 27.2% of the study area suffered flooding higher than 100 mm in rainfall events with return periods of 2, 200 and 1000 years respectively. 18.6%, 27% and 28.2% of the study area suffered flooding higher than 250 mm in rainfall events with duration of 60, 180 and 300 min respectively. Moreover, results indicate that flooding is centralised in Kowloon Bay Area, Lung Cheong Road, Kai Yip Estate and Choi Hung Estate. The simulation-based flooding assessment framework provided a basis for investigating spatial-temporal patterns and conducting risk assessment of frequent flooding.