Report No. : GEO Report No. 212

Report Title : Review of the 20 August 2005 Debris Flood at Lo Wai, Tsuen Wan (2007), 102 p.

Author : Maunsell Geotechnical Services Limited

Abstract

This report presents the findings of a review of the debris flood that occurred some time between 4:15 p.m. and 5:00 p.m. at Lo Wai, Tsuen Wan on 20 August 2005. The debris flood was probably triggered by two major landslides (Incident No. 2005/08/0338) on slope No. 7SW-A/CR134, which is situated immediately above the section of the Shing Mun Catchwater north of Lo Wai. Four other slopes Nos. 7SW A/F76, 7SW A/F77, 7SW A/F38 and 7SW A/CR132 located along the debris trail were caused to fail (Incidents Nos. 2005/08/0348, 2005/08/0402, 2005/08/0528 and 2005/08/0417). The incident also resulted in temporary evacuation of 118 residents and 84 visitors to the temples. A section of Lo Wai Road was temporarily closed.

The key objectives of the review were to document the facts about the debris flood and associated landslides, present relevant background information and establish the probable causes of the debris flood and associated landslides. The scope of the review comprised site reconnaissance, desk study and engineering analysis.

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