Proceedings of the
8th International Symposium on Geotechnical Safety and Risk (ISGSR)
14 – 16 December 2022, Newcastle, Australia
Editors: Jinsong Huang, D.V. Griffiths, Shui-Hua Jiang, Anna Giacomini, Richard Kelly
doi:10.3850/978-981-18-5182-7_11-022-cd
The Landslide Screening Criteria in Hong Kong Considering Rainfall Intensity and Topography
1State Key Laboratory of Internet of Things for Smart City and Department of Civil and Environmental Engineering, University of Macau, Macao, China.
2Department of Civil and Environmental Engineering, the Hong Kong University of Science and Technology, Hong Kong, China.
ABSTRACT
Rain-induced landslides are recognized as one of the most catastrophic hazards on hilly terrains. To develop strategies for landslide risk assessment and management, it is necessary to estimate not only the rainfall thresholds for triggering landslides, but also the topography effects on landslide travel distances. Empirical correlations between the scar area ratios of hillside landslides or channelized debris flows and the maximum rolling rainfall intensities with different periods have been derived. Topographic screening criteria are proposed based on distal elevation of landslides and distance from the nearest building. There are 2383 open hill slope landslides with an area ranging from 10 m2 to 30 m2. While the chanelized debris flows with a scar area ranging from 100 m2 to 200 m2 take a large proportion. The average values of scar area for the open hillslope and chanelized debris flows are 55.2 and 91.3 m2, respectively. The average values of horizontal distance for the open hillslope and channelized debris flows are 24.2 and 86.1 m, respectively. There are 1751 open hillslope landslides and 1063 channelized debris flows with crown slope angles ranging from 35º to 40º, which account for the largest proportion. Few landslides have a crown slope angle greater than 65º. The most common distal-end toe angles range is 25 to 30º. Few landslides have a distal-end toe angle greater than 55º. The thresholds of rainfall intensities with durations of 1-, 2-, 4-, 5-, 6-, 8-, 12-, and 24-hr are 77.5, 48.3, 28.1, 22.7, 19.7, 18, 15.2, 8.2 mm/hr, respectively. The landslides with horizontal distances from the nearest buildings <200 m, and distal downslope angles > 20º are likely to lead to direct risks to citizens. The topographic screening criteria considering the distal downslope angle, elevation, and distance from the nearest building are recommended. The study is expected to provide a sound basis for building an early warning system in Hong Kong.
Keywords: Rainfall, landslide consequences, landslide management, risk; proximity, Hong Kong.
