Monday January 16, 2006, Centennial Theatre Landslide Risk Management for Berkley-Riverside...

Monday January 16, 2006, Centennial Theatre

Landslide Risk Management for Berkley-Riverside

EscarpmentPresentation 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.


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


Hong Kong (1972)

Po Shan Road Landslide


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!


Berkley Landslide Risk Management Program

Initiation Decision to use proactive risk management to guide landslide risk reduction program. DNV risk managementteam is identified.

Preliminary Review causes, triggers, behaviour and consequences ofAnalysis previous landslides.

Risk Estimation Apply a systematic and transparent methodology to rate landslide hazards on the basis of likelihood of occurrence,vulnerability of infrastructure, and consequences of failure.

Risk Evaluation Determine tolerable risk. Allocate investigation, monitoringand stabilization budet to top-rated sites exceeding tolerable risk threshold.

Risk Control Identify feasible risk control options (monitoring and inspection,improve surface water management, physical stabilization, orland sterilization).

Action/ Implement chosen risk control options. Re-rate landslide risksMonitoring to evaluate effectiveness of risk control options. Ongoing

monitoring.(In

cid

en

t R

ep

ort

s, R

atin

gs,

Sta

bili

zatio

n R

ep

ort

s, a

nd

Mo

nito

rin

g D

ata

Po

ste

d o

n W

eb

)

Ris

k C

om

mu

nic

atio

n


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


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


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


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

19o 21o 23o 25o


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

>25o

>23o

>21o

>19o


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


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


Individual Risk

Risk faced by a single individual exposed to one or more landslide hazards

Hong Kong:• Existing slopes: 10-4 per year (1:10,000)

• New development: 10-5 per year (1:100,000)


What Does 10-4 per year Mean?

10-4 per year = 0.0001 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


Individual Risk Estimates for Berkley-Riverside

Risk > 10-4 per year

• 51 properties at base

• 1 property at crest

Risk = 10-4 to 10-5 per year

• additional 56 properties

Risk < 10-5 per year

• rest of escarpment


Societal Risk

Risk imposed upon the community by a single landslide

Hong Kong:

• F-N Curves


Societal Risk

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1 10 100 1,000 10,000

Number (N) of Fatalities

Fre

qu

enc

y (F

) o

f F

ata

litie

s (p

er y

r)

UNACCEPTABLE

ALARP

BROADLY ACCEPTABLE

INTENSE SCRUTINY

REGION


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


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


Monitoring Program


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)


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


Thank You

Date post:	02-Apr-2015
Category:	Documents
Upload:	mayra-kimery
View:	212 times
Download:	0 times

Monday January 16, 2006, Centennial Theatre Landslide Risk Management for Berkley-Riverside...

Documents