Likely Scenarios of Natural Terrain Shallow Slope Failures on Hong Kong Island under Extreme Storms

Abstract

In Hong Kong, rain-induced shallow slope failures are recognized as one of the most catastrophic hazards due to Hong Kong’s hilly terrain and frequent heavy storms. Due to climate changes, extreme storms are expected to be more frequent and intense in the future. The prediction of shallow slope failures under extreme storms is therefore essential. This study aims at simulating likely shallow slope failures on western Hong Kong Island under extreme storms. The terrain and slopes are discretized into a grid of cells on a geographical information system. Then, the pore-water pressure regime in the ground is analyzed through an infiltration analysis. Next, the slope stability and debris movement are assessed using a well-established model, which has been validated with landslides triggered in two past storm events. Finally, the shallow slope failures under three extreme storms at 44, 65, and 85% of the probable maximum precipitation are simulated. Under such extreme storms, more than 300 major slope failures may occur, occupying 0.5–1.7% of the natural terrain area. Some of the simulated movement traces and deposition locations are close to the urban area, calling for new strategies for landslide risk management.