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Quantitative Risk Assessment (QRA)

Quantitative Risk Assessment

"Slope Safety" is a long-term programme of sustained effort on all fronts to achieve the quickest possible reduction in landslide risk to the community in Hong Kong. The use of Quantitative Risk Assessment (QRA) technique in evaluating and managing landslide risk is gradually becoming recognized by the geotechnical practitioners in Hong Kong. This has led to a number of developments and applications of the technique to landslide problems in recent years. This web page provides a brief summary of the basic risk concepts and some pilot applications of QRA to geotechnical problems in Hong Kong. The creation of this web page is to facilitate the promulgation of pilot development work and the findings of these studies.


Using the technique of QRA, it was shown that the overall landslide risk arising from old substandard man-made slopes in Hong Kong had been reduced to less than 25% of the 1977 level by 2010, through the Government's Landslip Preventive Measures (LPM) Programme.



Basic Concepts

Terminology

Acceptable Risk:

A risk for which, for the purposes of life or work, society is prepared to accept as it is with no regard to its management. Society does not generally consider expenditure in further reducing such risk justifiable (IUGS Working Group on Landslides, 1997).


ALARP (as low as reasonably practicable):

The risk is regarded as tolerable only if risk reduction is impracticable or if the cost is grossly disproportionate to the improvement gained. This involves determining (HSE, 1992):

  1. whether a given risk is so great or the outcome so unacceptable that it must be refused altogether; or
  2. whether the risk is, or has been made, so small that no further precaution is necessary; or
  3. if a risk falls between these two states, that it has been reduced to the lowest level practicable, bearing in mind the benefits flowing from its acceptance and taking into account the costs of any further reduction. The injunction laid down in safety law is that any risk must be reduced so far as reasonably practicable, or to a level which is 'as low as reasonably practicable'.

Element at Risk:

Meaning the population, buildings and engineering works, economic activities, public services utilities and infrastructure in the area potentially affected by landslides (IUGS Working Group on Landslides, 1997).


Event Tree Analysis (ETA):

A technique, which can be either qualitative or quantitative, used to identify the possible outcomes and, if required, their probabilities, given the occurrence of an initiating event (CSA, 1991).


Fault Tree Analysis (FTA):

A technique, which can be either qualitative or quantitative, by which conditions and factors that can contribute to a specified undesired event (called the top event) are deductively identified, organized in a logical manner and represented pictorially (BSI, 1996).


F-N Curve:

v A plot showing, for a specified hazard, the frequency of all events causing a stated degree of harm to N or more people (Jones, 1992).


Hazard:

A physical situation with the potential for causing an undesirable consequence. Descriptions of landslide hazard, particularly for zoning purpose, should include the characteristics of the landslides, which may include the volumes or areas of the landslides and the probability of their occurrence. There may also be value in describing the velocities, and differential velocities of the landslide. Alternatively, the hazard is the probability a particular landslide occurs within a given time (IUGS Working Group on Landslides, 1997).


Hazard Identification:

The recognition that a hazard exists and the definition of its characteristics (CSA, 1991).


Individual Risk:

The risk of fatality and/or injury to any identifiable individual who lives within the zone exposed to landslide, or who follows a particular pattern of life that might subject him or her to consequences of the landslide (IUGS Working Group on Landslides, 1997).


Probability:

The likelihood of a specific outcome, measured by the ratio of specific outcomes to the total number of possible outcomes. Probability is expressed as a number between 0 and 1, with 0 indicating an impossible outcome, and 1 indicating that an outcome is certain (IUGS Working Group on Landslides, 1997).


Risk:

A measure of the probability and severity of an adverse effect to health, property, or the environment. It is often estimated by the product of probability and consequences. However, a more general interpretation of risk involves probability and consequences in a non-product form. This presentation is sometimes useful in that a spectrum of consequences with each magnitude having its own probability of occurrence is outlined (also see F-N curve) (CSA, 1991; IUGS Working Group on Landslides, 1997).


Risk Analysis:

The use of available information to estimate the risk to individuals or populations, property or the environment, from hazards. Risk analyses generally contain the following steps: scope definition, hazard identification, and risk estimation. (CSA, 1991; IUGS Working Group on Landslides, 1997).


Risk Assessment:

The process of risk analysis and risk evaluation (CSA, 1991; IUGS Working Group on Landslides, 1997).


Risk Control:

The process of decision-making for managing risk, and the implementation, enforcement, and re-evaluation of its effectiveness from time to time, using the results of risk assessment as one input (CSA, 1991).


Risk Criteria:

A qualitative and quantitative statement of the acceptable standard of risk with which the assessed risk needs to be compared (Royal Society, 1992)


Risk Estimation:

The process used to produce a measure of the level of health, property, or environmental risks being analysed. Risk estimation contains the following steps: frequency analysis, consequence analysis and their integration (CSA, 1991; IUGS Working Group on Landslides, 1997).


Risk Evaluation:

The stage at which values and judgements enter the decision process, explicitly or implicitly, by including consideration of the importance of the estimated risks and the associated social, environmental, and economic consequences, in order to identify a range of alternatives for managing the risks (CSA, 1991; IUGS Working Group on Landslides, 1997).


Risk Management:

The complete process of risk assessment and risk control (CSA, 1991; IUGS Working Group on Landslides, 1997).


Societal Risk:

The risk of multiple injuries or deaths to society as a whole: one where society would have to carry the burden of a landslide accident causing a number of deaths, injuries, financial, environmental, and other losses (IUGS Working Group on Landslides, 1997).


System:

A bounded, physical entity that achieves in its environment a defined objective through interaction of its part. This definition implies that (a) the system is identifiable, (b) the system is made up of interacting parts or subsystems, (c) all the parts must be identifiable, and (d) the boundary of the system can be identified (CSA, 1991).


Tolerable Risk:

A risk that society is willing to live with so as to secure certain net benefits in the confidence that it is being properly controlled, kept under review and further reduced as and when possible (IUGS Working Group on Landslides, 1997).


Top Event:

The selected outcome whose possible causes are analyzed in a fault tree (Jones, 1992).


Vulnerability:

The degree of loss to a given element or set of elements within the area affected by the landslide(s). It is expressed on a scale of 0 (no loss) to 1 (total loss). For property, the loss will be the value of the property; for persons, it will be the probability that a particular life (the element at risk) will be lost, given the person is affected by the landslide (IUGS Working Group on Landslides, 1997).


Reference

BSI (1996). Risk Management - Part 3: Guide to Risk Analysis of Technological Systems (BS 8444: Part 3: 1996, IEC 300-3-9: 1995). British Standards Institution, London, UK, 32p.


CSA (1991). Risk Analysis Requirements and Guidelines. Toronto, Canada, CAN/CSA-Q634-91. Canadian Standards Association, 42p.


HSE (1992). The Tolerability of Risk from Nuclear Power Stations. Health and Safety Executive, London, 61p.


International Union of Geological Sciences (IUGS) Working Group on Landslides, Committee on Risk Assessment (1997). Quantitative risk assessment for slopes and landslides - The state of the art. Proceedings of the Landslide Risk Workshop, IUGS Working Group on Landslides, Honolulu, pp 3-12.


Jones, D. (1992). Nomenclature for Hazard and Risk Assessment in the Process Industries. Institution of Chemical Engineers, 49p.


Royal Society (1992). Risk: Analysis, Perception and Management. Report of the Royal Society Study Group, London, 201p.




Components of Quantitative Risk

Assessment (QRA) Process

General

In general, QRA process includes risk analysis, risk assessment and risk management (Canadian Standards Association, 1991; IUGS Working Group on Landslides, 1997). Stewart (2000) further emphasized the importance of communication throughout the process of risk management, which is the systematic application of management policies, procedures and practices to the tasks of analyzing, evaluating, controlling, and communicating about risk issues. Figure 1 illustrates the relationship between risk analysis, risk assessment and risk management for a decision-making model.


Risk Analysis

Risk analysis consists of the following activities:


Initiation

Initiation includes defining the system, identifying risk management team and potential stakeholders. The system to be considered (e.g. slope) should be first defined in which information on the facility is collected and assimilated. The responsibility and authority of the risk management team members, and resources should then be assigned.


Hazard identification

Hazard identification is usually the first and the most critical step in a risk assessment. In this process, all relevant potential hazards covering the full range of incidents from minor frequent events to rare larger disasters are identified by techniques such as past experience, historical records, checklists, hazard index method, preliminary hazard analysis (PHA) and hazard and operability (HAZOP) study.


Frequency analysis

Frequency analysis is a process that estimates the frequency of each of the hazardous events identified at the hazard identification stage based on historical records, analytical or numerical techniques, or a combination of them.


Consequence analysis

Consequence analysis is carried out to establish all the possible consequences caused by each of the hazardous events in consideration of the vulnerability of those elements at risk in the event of failure. It is therefore an assessment of the conditional probability of the consequences occurring given the occurrence of a hazard.


Risk estimation

Risk estimation is a mathematical process that integrates the frequencies and consequences of each hazardous event into the levels of risk. The calculation is essentially a manipulation of the probability of failure, P(F) and the consequences of failure, P(C|F). Numerically, this can be expressed as:



Risk = P(F) x P(C|F)

Risk Assessment

Risk assessment is the process consisting of risk analysis and risk evaluation. Risk analysis is a series of activities of using available information to estimate the risk to individuals or populations, property, or the environment, from hazards. It generally contains system definition, hazard identification, frequency and consequence analyses, and risk estimation. For details of each activity, please refer to paragraphs under the caption of risk analysis. Risk evaluation refers to the stage at which values and judgements enter the decision process, explicitly or implicitly, by including consideration of the importance of the estimated risks and the associated social, environmental, and economic consequence, in order to identify a range of alternatives for managing the risks.


Risk Management

Risk management is the complete process of risk assessment, risk control, and implementation of action and/or monitoring plan. Risk control involves the evaluation of options for risk treatment, including risk mitigation, risk acceptance, and risk avoidance. The plan of action and/or monitoring is then implemented in accordance with the results of risk control process. In simple terms, QRA is used to address the following questions:


What can cause harm? ==>landslide hazard identification
How often? ==> frequency of occurrence of failure
What can go wrong? ==> consequence of failure
How bad? ==> severity of failure consequence
So what? ==> acceptability of landslide risk
What should be done? ==> landslide risk management


Reference

Canadian Standards Association (1991). Risk Analysis Requirements and Guidelines. Toronto, Canada, CAN/CSA-Q634-91. Canadian Standards Association.


International Union of Geological Sciences (IUGS) Working Group on Landslides, Committee on Risk Assessment (1997). Quantitative risk assessment for slopes and landslides - The state of the art. Proceedings of the Landslide Risk Workshop, IUGS Working Group on Landslides, Honolulu, pp 3-12.


Stewart, R.A. (2000). Dam Risk Management (Invited Paper). Proceedings of the International Conference on Geotechnical and Geological Engineering (GeoEng2000). Melbourne, pp. 721-748.



Risk Perception

General

'Risk' is a complex concept to the general public who may interpret it as something involves probability, consequence, and something implying monetary or other loss. Risk perception involves people's beliefs, attitudes, judgements, feelings, social or cultural values, etc. The factors affecting risk perception include (Melcher, 1993; Royal Society, 1992):
the likely consequences should an accident occur,
the uncertainty in that consequence estimate,
the perceived possibilities of obviating the consequences or reducing the probability of the consequences occurring, or both,
familiarity with the 'risk',
level of knowledge and understanding of the 'risk' or consequences or both, and
the interplay between political, social and personal influences in forming perceptions.


Acceptable Risk vs Tolerable Risk

'Acceptable' risk does not mean that it is 'tolerable'. For a risk to be acceptable, it means that for the purposes of life or work, one is prepared to take it well as it is. On the other hand, to tolerate a risk means that one does not regard it as negligible or something one might ignore, but rather as something one needs to keep under review and reduce still further if and as one can (HSE, 1992; Royal Society, 1992).


Regulation of Risk

The most fundamental approach to the setting of tolerable risk levels is based on the HSE's (1992) development of the ALARP (As Low As Reasonably Practicable) principle for nuclear power stations. In this approach there is an upper limit of risk above which it cannot be tolerated and it must be refused in any circumstance, and there is a lower limit below which risk is of no practical interest. Between the two limits is the region that risk must be reduced to a level 'as low as reasonably practicable' (ALARP). The legal interpretation of ALARP is well established in English case law in that the "sacrifice involved in the measures necessary for averting the risk (whether in money, time or trouble)" is not grossly disproportionate to the benefit obtained. Figure 2 illustrates the levels of risk and the ALARP principle.


Establishment of Tolerable Landslides and Boulder Falls Risk Levels

A pilot study has been carried out to investigate the public perception and tolerability of landslide risk in Hong Kong (The University of Hong Kong, 1998). It is found that the general public has greater tolerability of risk from their own perspective than from the societal point of view. In addition, the study has achieved the objective well in experimenting various surveying methods in collecting data on risk perception and Willingness to Pay.
At present, interim risk guidelines are available for natural terrain landslide and boulder fall hazards (ERM-Hong Kong, 1998). They are based on the existing guidelines on land use planning in the vicinity of Potentially Hazardous Installations (PHIs). The recommended interim societal risk criteria for landslides and boulder falls from natural terrain are shown in Figure 3.


Reference

HSE (1992). The Tolerability of Risk from Nuclear Power Stations. Health and Safety Executive, London.


ERM-Hong Kong Ltd (1998). Quantitative Risk Assessment of Boulder Fall Hazards in Hong Kong: Phase 2 (GEO Report No. 80). Report prepared for the Geotechnical Engineering Office, Hong Kong, 61 p.


Melchers, R.E. (1993). Society, tolerable risk and the ALARP principle. Probabilistic Risk Hazard Assessment, Melchers, R.E and Stewart, M.G. ed., pp. 243-252.


Royal Society (1992). Risk: Analysis, Perception and Management. Report of the Royal Society Study Group, London.


The University of Hong Kong (1998). Public Perception and Tolerability of Landslide Risk. Report prepared for the Geotechnical Engineering Office, Hong Kong.



Publications

Methodology

Atkins China Ltd (1999). Scoping Study for a Global Quantitative Risk Assessment on Natural Terrain Landslides in Hong Kong. Report prepared for the Geotechnical Engineering Office, Hong Kong.


Atkins Haswell (1995). QLRA for the Squatter Villages in Lei Yue Mun - Calculation of the Value of Lives Saved through Re-housing of Squatters from Lei Yue Mun. Report prepared for the Geotechnical Engineering Office, Hong Kong, 21 p.


Ayotte, D. & Hungr, O. (1998). Runout Analysis of Debris Flows and Debris Avalanches in Hong Kong. Report prepared for the Geotechnical Engineering Office, Hong Kong.


ERM-Hong Kong Ltd (1995). Quantitative Risk Assessment of Boulder Fall Hazards in Hong Kong: Phase 2 Study. Report prepared for the Geotechnical Engineering Office, Hong Kong.


ERM-Hong Kong Ltd (1998). Feasibility Study for QRA of Boulder Fall Hazards in Hong Kong (GEO Report No. 80). Report prepared for the Geotechnical Engineering Office, Hong Kong, 61 p.


Evans, N.C. & King, J.P. (1998). Debris Avalanche Susceptibility (Technical Note TN1/98). Geotechnical Engineering Office, 96 p.


Evans, N.C., Huang, S.W. & King, J.P. (1997). The Natural Terrain Landslide Study - Phases I and II (GEO Report No. 73). Geotechnical Engineering Office, 119 p.


Finlay, P.J. & Fell, R. (1995). A Study of Landslide Risk Assessment for Hong Kong. Report prepared for the Geotechnical Engineering Office, Hong Kong.


Golder Associates (HK) Ltd (1996). Report on Development of a QRA Methodology for Landslides on Natural Terrain in Hong Kong. Report prepared for the Geotechnical Engineering Office, Hong Kong.


Hungr, O. (1998). Mobility of Landslide Debris in Hong Kong: Pilot Back Analyses using a Numerical Model. Report prepared for the Geotechnical Engineering Office, Hong Kong.


Lau, K.C. & Woods, N.W. (1997). Review of Methods for Predicting the Travel Distance of Debris from Landslides on Natural Terrain (Technical Note TN 7/97). Geotechnical Engineering Office, 48 p.


Maunsell Geotechnical Services Ltd (1999). Territory Wide Quantitative Risk Assessment of Boulder Fall Hazards - Stage 1 Final Report. Report prepared for the Geotechnical Engineering Office, Hong Kong.



Data Compilation

Atkins China Ltd (1998). Consequence Classification System of Mass Transportation Facilities. Report prepared for the Geotechnical Engineering Office, Hong Kong.


ERM-Hong Kong Ltd (1995). Landslide Consequence Severity Classification of Roads and Footpaths. Report prepared for the Geotechnical Engineering Office, Hong Kong, 101 p.


Golder Associates (HK) Ltd (1996). Finalisation of the Priority Classification System for Rock Cut Slopes. Report prepared for the Geotechnical Engineering Office, Hong Kong.


King, J.P. (1999). Natural Terrain Landslide Study the Natural Terrain Landslide Inventory (GEO Report No. 74). Geotechnical Engineering Office, 127 p.


MMBP (1996). Compilation of a Database on Landslide Consequence. Report prepared for the Geotechnical Engineering Office, Hong Kong.


Scott Wilson (Hong Kong) Ltd (1999). Specialist API Services for the Natural Terrain Landslide Study for Agreement No. CE 39/98 (Interpretative Report, Factual Report and 8 other Technical Reports and Data Table Reports). Report prepared for the Geotechnical Engineering Office, Hong Kong.


Wong, C.K.L. (1998). The New Priority Classification Systems for Slopes and Retaining Walls (GEO Report No. 68). Geotechnical Engineering Office, 117 p.


Wong, H.N. & Ho, K.K.S. (1995). New Priority Classification System for Soil Cut Slopes (Special Project Report SPR 6/95). Geotechnical Engineering Office, 57 p.



Risk Perception

ERM-Hong Kong Ltd (1998). Landslides and Boulder Falls from Natural Terrain: Interim Risk Guidelines (GEO Report No. 75). Report prepared for the Geotechnical Engineering Office, Hong Kong, 183 p.


Sun, H.W. & Evans, N.C. (2001). Comparative Risk Indicators (Special Project Report SPR 1/2001). (Also in GEO Report No. 128) Geotechnical Engineering Office, 26 p.


University of Hong Kong (1998). Public Perception and Tolerability of Landslide Risk. Report prepared for the Geotechnical Engineering Office, Hong Kong.



Application

Site Specific Application

QRA


Others

Chan, W.L., Ho, K.K.S. & Sun, H.W. (1998). Computerised Databases of Landslides in Hong Kong. Proceedings of the Hong Kong Institution of Engineers Geotechnical Division Annual Seminar on Slope Engineering in Hong Kong, Balkema, pp 213-220.


Cheng, P.F.K. (2011). Assessment of Landslide Risk Posed by Man-made Slopes as of 2010 (Special Project Report SPR 1/2011). Geotechnical Engineering Office, 12 p.


Cheng, P.F.K. & Ko, F.W.Y. (2010). An Updated Assessment of Landslide Risk Posed by Man-made Slopes and Natural Hillsides in Hong Kong (GEO Report No. 252). Geotechnical Engineering Office, 46 p.


Cheung, W.M. & Shiu, Y.K. (2000). Assessment of Global Landslide Risk Posed by Pre-1978 Man-made Slope Features: Risk Reduction from 1977 to 2000 Achieved by the LPM Programme (GEO Report No. 125). Geotechnical Engineering Office, Hong Kong, 61 p.


DNV (1996). Quantitative Landslip Risk Assessment of Pre-GCO Man-made Slopes and Retaining Walls (Phase 1). Report prepared for the Geotechnical Engineering Office, Hong Kong.


ERM-Hong Kong Ltd (1999). Slope Failures along BRIL Roads: Quantitative Risk Assessment and Ranking (GEO Report No. 81). Report prepared for the Geotechnical Engineering Office, Hong Kong, 200 p.


Fugro (Hong Kong) Ltd. (2004). Quantitative Risk Assessment of Landslides Affecting Squatters. Report prepared for the Geotechnical Engineering Office, Hong Kong.


Hardingham, A., Lo, D.O.K., Ho, K.K.S. & Chase, E. (1999). Landslide Consequence Assessment for High-speed Mass Transportation Facilities. Proceedings of the Hong Kong Institution of Engineers Geotechnical Division Annual Seminar on Geotechnical Risk Management, Hong Kong, pp 43-53.


Hardingham, A.D., Ho, K.K.S., Smallwood, A.R.H. & Ditchfield, C.S. (1998). Quantitative Risk Assessment of Landslides - A Case History from Hong Kong. Proceedings of the Hong Kong Institution of Engineers Geotechnical Division Annual Seminar on Slope Engineering in Hong Kong, Balkema, pp 145-152.


Ho, K.K.S. & Ko, F.W.Y. (2007). Application of Quantified Risk Analysis in andslide Risk Management Practice - Hong Kong Experience. Proceedings of International Symposium on Geotechnical Safety and Risk 2007, Shanghai, pp 3-51.


Ho, K.K.S., Leroi, E. & Roberds, W.J. (2000). Quantitative Risk Assessment Application, Myths and Future Direction (Issues Paper). Proceedings of the International Conference on Geotechnical and Geological Engineering (GeoEng2000), Melbourne, pp 269-312


Lo, D.O.K.(2002) Interim Review of Pilot Applications of Quantitative Risk Assessment to Landslide Problems in Hong Kong. (GEO Report No. 126). Geotechnical Engineering Office, Hong Kong,71p


Lo, D.O.K. & Cheung, W.M. (2004). Assessment of Landslide Risk of Man-made Slopes in Hong Kong (GEO Report No.177). Geotechnical Engineering Office, Hong Kong,82p


Malone, A.W. (1998). Risk Management and Slope Safety in Hong Kong. Proceedings of the Hong Kong Institution of Engineers Geotechnical Division Annual Seminar on Slope Engineering in Hong Kong, Balkema, pp 3-20.


Maunsell Geotechnical Services Ltd (2001). Territory Wide Quantitative Risk Assessment of Boulder Fall Hazards. Report prepared in association with ERM for the Geotechnical Engineering Office, Hong Kong.


Ove Arup & Partners Hong Kong Ltd (1999). QRA of Collapses and Excessive Displacements of Deep Excavations (GEO Report No. 124). Report prepared for the Geotechnical Engineering Office, Hong Kong.


Reese, A., Ho, K.K.S. & Lo, D.O.K. (1999). Interim Risk Criteria for Landslides and Boulder Falls from Natural Terrain. Proceedings of the Hong Kong Institution of Engineers Geotechnical Division Annual Seminar on Geotechnical Risk Management, Hong Kong, pp 127-136.


Reeves, A., Chan, H.C. & Lam, K.C. (1998). Preliminary Quantitative Assessment of Boulder Falls in Hong Kong. Proceedings of the Hong Kong Institution of Engineers Geotechnical Division Annual Seminar on Slope Engineering in Hong Kong, Balkema, pp 185-192.


Roberds, W.J. & Ho, K.K.S. (1997). A Quantitative Risk Assessment and Risk Management Methodology for Natural Terrain in Hong Kong. Proceedings of the First International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction, and Assessment, California, pp 207-218.


Roberds, W.J., Ho, K.K.S. & Leung, K.W. (1997). An Integrated Methodology for Risk Assessment and Risk Management for Development below Potential Natural Terrain Landslides. Proceedings of the Hong Kong Institution of Engineers Geotechnical Division Annual Seminar on Slope Engineering in Hong Kong, Balkema, pp 333-346.


Sun, H.W. & Evan, N.C. (1999). The Average Annual Global Risk from Natural Terrain Landslides in Hong Kong in 1994 (Technical Note TN 5/99). Geotechnical Engineering Office, 44 p.


Wong, C.K.M. & Lee, C.K.T. (1999). Application of Quantitative Landslide Risk Assessment in Hong Kong. Proceedings of the International Symposium on Slope Stability Engineering: Geotechnical and Geoenvironmental Aspects, Shikoku, Japan, pp 1303-1307.


Wong, H.N. (2005). Landslide risk assessment for individual facilities. Proceedings of the International Conference on Landslide Risk Management, Vancouver, Canada, pp 237-296.


Wong, H.N. & Ho, K.K.S. (1998). Overview of Risk of Old Man-made Slopes and Retaining Walls in Hong Kong. Proceedings of the Hong Kong Institution of Engineers Geotechnical Division Annual Seminar on Slope Engineering in Hong Kong, Balkema, pp 193-200.


Wong, H.N. & Ho, K.K.S. (2000). Preliminary Quantitative Risk Assessment of Earthquake-induced Landslides at Man-made Slopes in Hong Kong (GEO Report No. 98). Geotechnical Engineering Office, 69 p.


Wong, H.N. & Ho, K.K.S. (1999). Preliminary Quantification of Risk of Earthquake-induced Failure of Man-made Slopes in Hong Kong. Proceedings of the Hong Kong Institution of Engineers Geotechnical Division Annual Seminar on Geotechnical Risk Management, Hong Kong, pp 67-76.


Wong, H.N. & Ho, K.K.S. (2006). Landslide risk management and slope engineering in Hong Kong. Proceedings of the State-Of-The-Practice of Geotechnical Engineering in Taiwan and Hong Kong, Hong Kong, pp 101-141.


Wong, H.N., Ho, K.K.S. & Chan, Y.C. (1997). Assessment of Consequence of Landslides. Proceedings of the Workshop on Landslide Risk Assessment, IUGS Working Group on Landslides, Honolulu, pp 111-149.


Wong, H.N., Ho, K.K.S. & Sun, H.W. (2006). The role of slope instrumentation in landslide risk management: Hong Kong experience. Proceedings of the Conference on Landslide, Sinkhole, Structure Failure: Myth or Science, Ipoh, Malaysia.


Wong, H.N., Ko, F.W.Y. & Hui, T.H.H. (2006). Assessment of Landslide Risk of Natural Hillsides in Hong Kong GEO Report No. 191). Geotechnical Engineering Office, Hong Kong, 117p.


Wong, H.N. & Ko, F.W.Y. (2006). Landslide Risk Assessment - Application and Practice (GEO Report No. 195). Geotechnical Engineering Office, Hong Kong, 277 p.