Scenarios of large-scale landslides and debris flows under extreme rainstorms

Rainfall-induced landslides and debris flows can cause great losses of both human lives and properties, especially on Hong Kong Island where the density of population is high and landslide and debris flow are active. In the changing climate, the frequency of the occurrence of landslides and debris flows is on a growing trend. Therefore, it is important to simulate possible scenarios of landslides and debris flows under extreme weather conditions. The objective of this paper is to simulate future landslides and debris flows on Hong Kong Island considering the influence of climate change. In this paper, a physically-based models are implemented. The slope stability analysis is conducted and the movement traces and locations of landslides are predicted to determine the initiation locations of debris flows under three reference rainstorms (i.e. 44%, 65% and 85% of the 24-h probable maximum precipitation, PMP). Then debris flows initiated at indicated locations are predicted. With the increase of rainstorm magnitude, the landslide and debris flow magnitudes grow dramatically. Also, many debris flows can occur simultaneously and merge under extreme storms, posing much greater threat to people’s lives and properties.