Report No. : GEO Report No. 196

Report Title : The 5 May 2003 Debris Flow at Kau Lung Hang Shan Tai Po (2006), 84 p. plus 1 drg.

Author : Maunsell Geotechnical Services Limited

Abstract

This report presents the findings of an investigation into Incident No. 2003/05/0031, which involved a landslide on the natural hillside north of Kau Lung Hang Village, Tai Po. The landslide occurred during severe rainfall at about 4 a.m., approximately 1 hour prior to the hoisting of a Red Rainstorm Warning Signal.

The landslide involved a failure volume of about 200 m³. Some 180 m³ of the failed material detached from the source area and travelled down an ephemeral drainage line as a debris flow. The debris resulted in complete blockage of the sole access road to Cloudy Hill Transmitter Station for four days and severed a wire boundary fence of an orchard within private Lot No. 155 in D.D. 9 at the toe of the hillside below the access road. The runout distance of the main debris flow was about 165 m (disregarding the fluvial outwash). The deposition of fine grained fluvial outwash material continued for a further 20 m, reaching the boundary of two village houses (within the private Lot No. 155 in D.D. 9). No damage to these village houses was observed and no casualties were reported.

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