Report No. : GEO Report No. 75

Report Title : Landslides and Boulder Falls from Natural Terrain : Interim Risk Guidelines (1998), 183 p. (Reprinted, 1999)

Author : ERM-Hong Kong, Ltd.

Abstract

In 1993, the Geotechnical Engineering Office (GEO) embarked on a programme of research and development studies on landslide risk management under the R & D theme on Quantitative Risk Assessment, which encompasses evaluation of risk of landslides and boulder falls from natural terrain.

As part of the formulation of natural terrain landslide risk management strategy, it is necessary to establish appropriate tolerable risk criteria for risk assessment purposes. This study was carried out by Dr A.B. Reeves of ERM-Hong Kong, Ltd as consultants under the Consultancy Agreement No. GEO 4/97. Mr K.K.S. Ho and Dr D.O.K. Lo of the Special Projects Division coordinated the work.

In this report, two options are recommended for consideration as the interim risk guidelines. These have been developed based on a detailed review of current international practices and benchmarking against the risk acceptance criteria for Potentially Hazardous Installations (PHI) given in the Hong Kong Planning Standards and Guidelines dated 1993. A presentation of the initial findings was given by the consultants to CED colleagues and geotechnical consultants on 13 October 1997 and also to the Slope Safety Technical Review Board in the November 1997 meeting. Comments received have been taken into account in finalising the Report. The draft report of the study was also reviewed by Dr J. Wrigley of the Environmental Protection Department, whose assistance is gratefully acknowledged.

It is intended that the practicality of the recommended interim risk guidelines will be verified in site-specific quantitative risk assessment (QRA) studies of natural terrain landslide hazards. Suitable refinement will be made where necessary and the geotechnical profession will be widely consulted before the risk guidelines are finalised. In the meantime, the interim guidelines can be used as a basis for the evaluation of QRA results. This staged approach in taking forward the use of QRA techniques in the formulation of an assessment framework for natural terrain landslide hazards has been endorsed by the Secretary for Works.

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