LANDSLIDE HAZARD MAPPING METHODOLOGY FOR REGIONAL SCALE HAZARD ASSESSMENT, WEST LANTAU ISLAND, HONG KONG SAR, CHINA

Recently the Geotechnical Engineering Office (GEO) of the Hong Kong Government has implemented a new long-term Landslip Prevention and Mitigation Program (LPMP) that aims to create and implement methodologies for the identification of regional to site-specific landslide hazards.The natural terrain of West Lantau is the largest by far of the new LPMP projects, with an approximate study area of ~17km2. The project team is currently developing the methodology used to evaluate, identify, and classify landslide hazards for the West Lantau region of Hong Kong for the purpose of prioritizing 30 hillside catchment areas for mitigation.

Detailed geomorphological mapping was used to evaluate basic landform morphology and regolith type, with particular reference to landslide generation, and entrainment susceptibility. Geomorphic assessment was utilized to evaluate current geomorphological processes, with a focus on landslide initiation and debris transportation in order to generate a model of landscape evolution for the entire study area. This geomorphic model allowed creation of a terrain hazard model that groups morphology and geology, geologic processes, and past landslide occurrences in order to asses the regional landslide hazards and potential risk.

The West Lantau geomorphic maps were used as the basis of the interrogation of existing landslide inventories to derive a hazard map for the assessment of landslide severity; and ranking of catchments posing potential hazards to existing villages and transportation routes in order that 30 catchments could be prioritized for the next phase of detailed studies and hazard mitigation works.

Detailed engineering geological mapping with respect to the geological and geomorphological controls of the source areas completed at an regional scale allows for context and geographically contiguous hazard assessment methodologies, not only for the landslide prone West Lantau, but for future site specific and regional scale assessment of landslide hazards in Hong Kong.