Report No. : GEO Report No. 272

Report Title : Detailed Study of the 7 June 2008 Landslides on the Hillside above the North Lantau Highway and Cheung Tung Road, North Lantau (2012), 118 p.

Author : AECOM Asia Company Limited

Abstract

This report presents the findings of a detailed study of the natural terrain landslides that occurred on the hillside above North Lantau Highway (NLH), Tung Chung, Northern Lantau, on 7 June 2008 during a Black Rainstorm.

A total of 38 landslides occurred on the hillside above NLH; four of them developed into channelised debris flows (CDFs). The debris flows terminated within the drainage lines without affecting any toe facilities. However, debris flood occurred in three catchments, transporting a total of approximately 540 m³ of sediment/debris further downstream. The sediment/debris blocked the drainage system at the hillside toe along Cheung Tung Road, resulting in severe flooding of the adjoining NLH. The highway, which is the critical transport corridor to the Hong Kong International Airport, was temporarily closed for about 16 hours and reopened around 1:00 a.m. on 8 June 2008. No casualties were reported as a result of the landslides.

The study focuses on selected landslides with long runout distances. The key objectives were to document the facts about the long runout landslides, present relevant background information, establish the probable causes of the landslides and debris movement processes. The scope of the study comprised desk study, site reconnaissance, detailed field mapping, and engineering geological mapping. Recommendations for follow-up actions are presented separately.

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