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Summary of Findings of Landslide Investigation

The 2 July 1997 Landslide at Lido Beach, Castle Peak Road

Basic Data

Material: Decomposed Granite & Fill
Feature Affected: Partly Modified Natural Terrain & Fill Slope No. 6SE-C/F3
Volume: 750 m3
Report Reference: Geo Report No.89
Location of Landslide
Cross Section of Landslide Location plan

Description

The landslide occurred on a 15 m high, partly modified natural terrain and affected an adjacent fill slope that was formed in the 1950's upslope of Castle Peak Road.  Eight people were injured as a result of the landslide.

Debris from the landslide travelled some 70 m, completely blocking Castle Peak Road.  The travel angle of the debris was about 20o which reflects that the failure was mobile when compared to other rain-induced landslides of similar volume in Hong Kong.

The landslide involved two phases of detachment.  Eight people were trapped and injured by the debris associated with the second phase of failure.

The landslide was probably triggered by an increase in groundwater pressure in the slope caused by the effects of direct infiltration of rainwater and ponding within the uncovered area of  an abandoned property directly upslope of the landslide.



Observations

The incident highlights the need to properly address abandoned properties close to slope crests with regard to the potential for water ponding in unpaved platforms and effects on water pathways.

The incident also emphasizes the potential hazard involved in secondary failures and the need to take the necessary safety precautions when attending to landslide sites.