38
Geotechnical News • September 2018
GEOHAZARDS
Assessments (QRAs) should be
promoted that include the spec-
trum of probabilities for existing
and future development. A QRA
will then allow a risk-based de-
velopment decision without being
attached to a single frequency or
probability threshold.
• The Land Title Act and Community
Charter both specify that consul-
tants need to specify “the land may
be used safely for the use intend-
ed”. Such formalism in absence of
a definition of “safety” should be
replaced by quantifying risk for a
development and then its com-
parison to tolerable or acceptable
risk levels defined and adopted by
government. We understand and
welcome that the BC government
is working towards such solution
as conferring this critical risk tol-
erance decision to each municipal
or regional government places a
substantial burden on small gov-
ernments who have limited human
and monetary resources to develop
and justify such criteria.
• In light of budget limitations that
may prevent mitigation of existing
developments against the entire
spectrum of geohazard scenarios,
geotechnical monitoring and warn-
ing systems should be consid-
ered as an alternative to manage
residual landslide risk. This is
especially true for potentially
catastrophic landslides that may
prove to be unmitigatable. Moni-
toring and warning systems may
be useful to reduce risk to loss of
life for existing development, but
they should not encourage new
development in hazardous areas
because of in-perpetuity monitor-
ing and maintenance requirements.
While potentially expensive in
installation and maintenance, their
redundancies and sophistication
can be adjusted to the degree of
landslide activity observed.
The above recommendations can
only be devoted meaningfully to the
benefit of society if accompanied with
systematic inventories of landslide
geohazards and at least qualitative
risk-based hazard prioritization. This
should allow the identification of those
areas requiring more detailed study
and eventual mitigation. Guided by the
goal of improving landslide risk man-
agement in BC, and striving to reduce
catastrophic losses by practicable
means, the authors call on provincial
regulators to consider the suggestions
outlined above.
Acknowledgements
We thank
Doug VanDine
and
Gord
Hunter
for their thoughtful comments
on a draft of this contribution.
References:
EGBC, 2010. Guidelines for Land-
slide Assessments for Legislated
Residential Developments.
EGBC, 2012. Guidelines for Leg-
islated Flood Assessments in a
Changing Climate.
Cave, P. 1992/1993. Hazard accept-
ability thresholds for development
approvals by local government,
British Columbia. British Colum-
bia Geological Survey Branch,
Open File 1992-15.
Catani, F., Tofani, V., Lagomarsino, D.
2016. Spatial pattern of landslide
dimension: A tool for magnitude
mapping. Geomorphology. 271:
361-373.
Cheekeye Expert Review Panel #2.
2015. Cheekye River and Fan
Landslide Landslide Risk Toler-
ance Criteria. Final report.
Church, M. and Ryder, J.M., 1972.
Paraglacial Sedimentation: A
Consideration of Fluvial Pro-
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Geological Society of America
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Cruden, D.M., and Hu, X-Q. 1993.
Exhaustion and steady state mod-
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in the Canadian Rocky Mountains.
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Hantz, D., Vengeon, G.N., Dussauge-
Peisser, D. 2003. An historical,
geomechanical, and probabilis-
tic approach to rock fall hazard
assessment.
Hungr, O. 2004. Landslide hazards
in BC, achieving balance in risk
assessment. Innovation, April
2004.
Mathewes, R.W., and Heusser, L.E.,
1981. A 12 000 year palynological
record of temperature and precipi-
tation trends in southwestern Brit-
ish Columbia. Canadian Journal of
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MOTI, 2015. Subdivision Preliminary
Layout Review – Natural Hazard
Risk, June 2015 (internal docu-
ment, Victoria, BC).
Matthias Jakob, Ph.D., P.Geo.
(BC/AB), L.G.
Principal Geoscientist
Adjunct professor Geography and
Earth, Ocean and Atmospheric
Sciences, UBC
Suite 500 - 980 Howe Street
Vancouver, BC, Canada, V6Z 0C8
Tel: (604) 684-5900 , ext. 41112
Cell: (604) 367-5795
Facsimile: (604) 684-5909
Pierre Friele, P.Geo
Cordilleran Geoscience
PO Box 612, 1021 Raven Drive
Squamish, BC, Canada, V0N 3G0
(604) 898-4770
Michael Porter, M.Eng., P.Eng., LEG
Director, Principal Geological
Engineer, BGC Engineering Inc.
500 - 980 Howe Street
Vancouver, BC., V6Z 0C8
(604) 684-5900, ext. 41123
Direct: (604) 629-3847
Cell: (604) 240-8055
Facsimile:(604) 684-5909
Scott McDougall
Assistance Professor,
University of British Columbia
6339 Stores Road, EOS-South 255
Vancouver, BC V6T 1Z4
(604) 827-3864
