Report No. : GEO Report No. 154

Report Title : Detailed Study of the 1 September 2001 Debris Flow on the Natural Hillside above Lei Pui Street (2004), 129 p. plus 1 drg.

Author : Maunsell Geotechnical Services Ltd.

Abstract

This report presents the findings of an investigation into the landslide (GEO Incident No. 2001/09/0057), which occurred on 1 September 2001 above Lei Pui Street, Shek Lei Estate, Kwai Chung. The debris flow was triggered by a landslide involving about 250 m³ of rock and soil on the steep natural hillside above a 25 m high cliff. The landslide debris and entrained material with an estimated maximum volume of 780 m³ was deposited mainly within the lower part of the hillside and an active construction site, situated about 10 m above Lei Pui Street. About 50 m³ of outwash material was deposited on Lei Pui Street and the Shek Lei Estate. The landslide demolished two squatter structures which had been vacated about two hours before the event and Lei Pui Street was closed for 3 days. No casualties were reported.

The key objectives of the detailed study were to document the facts about the landslide, present relevant background information, establish the probable causes of the failure and present the key findings. The scope of the study comprised site reconnaissance, desk study, detailed mapping, ground investigation and laboratory testing, together with theoretical analyses.

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