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Monday January 16, 2006, Centennial Theatre Landslide Risk Management for Berkley-Riverside Escarpment Presentation to the Community January 16, 2006 Michael.

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Presentation on theme: "Monday January 16, 2006, Centennial Theatre Landslide Risk Management for Berkley-Riverside Escarpment Presentation to the Community January 16, 2006 Michael."— Presentation transcript:

1 Monday January 16, 2006, Centennial Theatre Landslide Risk Management for Berkley-Riverside Escarpment Presentation to the Community January 16, 2006 Michael Porter, M.Eng., P.Eng. Dr. Matthias Jakob, P.Geo. Dr. K. Wayne Savigny, P.Eng., P.Geo. BGC Engineering Inc.

2 Monday January 16, 2006, Centennial Theatre What We Know On January 19, 2005 a landslide killed Eliza Kuttner and seriously injured her husband At least 5 other landslides since 1972 all triggered by heavy rainfall Many other locations in the GVRD are subject to landslide hazards not unique

3 Monday January 16, 2006, Centennial Theatre Hong Kong (1972) Po Shan Road Landslide

4 Monday January 16, 2006, Centennial Theatre Hong Kong Slope Safety Program Principles of risk management and quantitative risk assessment Manage 58,000 registered slopes Dr. Norbert Morgenstern (U of A) on Advisory Panel Public education program State-of-the-art monitoring Hong Kong is now the world-leader in LRM Australia, California, Seattle, British Columbia Thousands of lives have been saved!

5 Monday January 16, 2006, Centennial Theatre Berkley Landslide Risk Management Program

6 Monday January 16, 2006, Centennial Theatre Work Completed to Date Detailed investigations in the vicinity of the January 2005 landslide: escarpment geology assessment of landslide cause assessment of residual risk Glacial Till Fill / Retaining Walls Marine Silt and Sand Colluvium

7 Monday January 16, 2006, Centennial Theatre Work Completed to Date Along Rest of Escarpment (Current Contract): inventory of past landslides evaluation of landslide-triggering storms rainfall and piezometer monitoring visual inspection and hand-auger drilling quantitative risk assessment

8 Monday January 16, 2006, Centennial Theatre Landslide Likelihood Estimates > 2 times Average ~ Average < ½ Average Subdivided crest into 75 Increments Rank based on: thickness of fill drainage conditions slope angle evidence of past movement

9 Monday January 16, 2006, Centennial Theatre Landslide Runout Consequence a function of the angle to the crest of the escarpment Seymour River Crest of Escarpment Landslide Initiation Zone Landslide Deposition Zone 19 o 21 o 23 o 25 o

10 Monday January 16, 2006, Centennial Theatre Landslide Runout Moderate to high likelihood of damage to homes Low to moderate likelihood of damage to homes Damage possible; mostly sedimentation and flooding Minor flooding >25 o >23 o >21 o >19 o

11 Monday January 16, 2006, Centennial Theatre Landslide Risk Estimates and Evaluation Potential for fatality at crest and base of escarpment To be safe, a property must pass two tests: risk to individuals must be tolerable societal risks must be tolerable

12 Monday January 16, 2006, Centennial Theatre Tolerable Risks Within a range society can live with Low, but not zero Less than other risks in everyday life Reduced further if practicable Limits defined in collaboration with the affected Community

13 Monday January 16, 2006, Centennial Theatre Individual Risk Risk faced by a single individual exposed to one or more landslide hazards Hong Kong: Existing slopes: per year (1:10,000) New development: per year (1:100,000)

14 Monday January 16, 2006, Centennial Theatre What Does per year Mean? per year = or a 1 in 10,000 chance of fatality per year of exposure Equivalent to average Canadian’s risk from motor vehicle accidents volvocanada.com

15 Monday January 16, 2006, Centennial Theatre Individual Risk Estimates for Berkley-Riverside Risk > per year 51 properties at base 1 property at crest Risk = to per year additional 56 properties Risk < per year rest of escarpment

16 Monday January 16, 2006, Centennial Theatre Societal Risk Risk imposed upon the community by a single landslide Hong Kong: F-N Curves

17 Monday January 16, 2006, Centennial Theatre Societal Risk

18 Monday January 16, 2006, Centennial Theatre Societal Risk Estimates for Berkley-Riverside Unacceptable Risk 22 source areas ALARP Zone 37 source areas Broadly Acceptable 16 source areas (Hong Kong Criteria) Assigned to the 75 source areas along escarpment crest

19 Monday January 16, 2006, Centennial Theatre Comments on Risk Estimates They match the historical record calibrated They represent a snapshot in time risk changes over time They do not account for: acquisition of 8 properties affected by the January 2005 landslide improvements to the storm sewer system increased public awareness of the hazards rainfall and piezometer monitoring program

20 Monday January 16, 2006, Centennial Theatre Monitoring Program

21 Monday January 16, 2006, Centennial Theatre Work Plan for Risk Reduction More investigation of top rated sites Evaluate viable risk control options: ongoing monitoring and inspection drainage improvements removal of unstable retaining walls removal or recompaction of unstable fills slope reinforcement (new retaining walls; soil nails) Quantify benefit and cost of each option Implement preferred option(s)

22 Monday January 16, 2006, Centennial Theatre Closing Remarks A risk management program has been initiated consistent with Canadian standards and international best practices Baseline risks have been estimated to prioritise sites for mitigation to facilitate evaluation of risk control options Risks are currently managed through monitoring We have an opportunity to apply best practices, exhibit leadership, and minimise the potential for future tragedy

23 Monday January 16, 2006, Centennial Theatre Thank You


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