Report No. : GEO Report No. 126

Report Title : Interim Review of Pilot Applications of Quantitative Risk Assessment to Landslide Problems in Hong Kong (2002), 71 p.

Author : D.O.K. Lo


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 (QRA). This has led to a number of pilot applications of QRA to landslide problems in Hong Kong.

In 1999, an interim review of some of the pilot applications of QRA to landslide problems in Hong Kong was carried out to examine the usefulness of QRA in such work and to identify the areas for further development. The review is documented in this Report.

While one may query about the details of some of the assumptions and methodologies in the pilot studies carried out, the studies have demonstrated that the QRA framework has been useful to help address issues that could not be tackled effectively by the conventional deterministic factor of safety approach. This interim review has shown that QRA can be a very valuable tool in landslide risk management. It has been applied to assess the cost of managing risk and the direct and indirect benefits, optimise the allocation of available resources, identify areas of concern for improvement, and measure and evaluate the effectiveness of the Slope Safety System. QRA can also be an effective vehicle for objective communication of risk amongst engineers, regulatory agencies, resources allocators and the public.

The interim review has identified factors that can affect the usefulness of QRA. These include scarcity of relevant or good quality data, low resolution of data for the purpose of assessment, lack of suitable verification data, insufficient knowledge about hazard and consequence modelling, influence of human factors, project constraints, etc. These are not specific to QRA itself but are identical to those that can affect the usefulness of any geotechnical engineering evaluation technique. Notwithstanding the above, QRA can provide valuable insights and perspectives beyond those that can be normally obtained from conventional deterministic methods. It helps to break down the problems into manageable sub-components to facilitate a better understanding of the critical elements. It provides a framework for evaluating uncertainties and exercising engineering judgement systematically. It also helps to identify effective solutions or to justify any acquisition of additional data prior to decision-making. Some areas of improvement to enhance the reliability of QRA that were identified during the course of the pilot studies are summarised in the Report.

The subject of QRA as applied to landslide risk assessment is evolving. Readers should note that since this interim review was completed in 1999, a number of other QRA studies have been carried out and further experience gained. Interested parties should refer to the relevant documentation on these to obtain a more complete picture of the current state of development.

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