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TitleSlope stability hazard in a fjord environment: Douglas Channel, Canada
AuthorStacey, C DORCID logo; Lintern, D GORCID logo; Shaw, J; Conway, K W
SourceGeological Society, Special Publication vol. 500, issue 1, 2020 p. 427-451,
Alt SeriesNatural Resources Canada, Contribution Series 20200133
PublisherThe Geological Society of London
Mediaon-line; digital
File formatpdf
ProvinceBritish Columbia
NTS103A/02; 103A/03; 103A/06; 103A/07; 103A/10; 103A/11; 103A/14; 103A/15
AreaDouglas Channel
Lat/Long WENS-129.5000 -128.5000 54.0000 53.0000
Subjectsenvironmental geology; geophysics; Health and Safety; marine geology; Nature and Environment; Science and Technology; sedimentology; soils science; surficial geology/geomorphology; slope stability; slope stability analyses; fiords; morphology; marine sediments; Assessment
Illustrationslocation maps; satellite imagery; tables; logs; plots
ProgramPublic Safety Geoscience Assessing landslides and marine geohazards
Released2020 05 20
AbstractDouglas Channel is a 140 km-long fjord system on Canada's west coast where steep topography, high annual precipitation and glacially over-deepened bathymetry have resulted in widespread slope failures. A 5 year project involving numerous marine expeditions to the remote area produced a comprehensive assessment of the magnitude and frequency of slope failures in the region. A classification scheme is presented based on morphology and failure mechanism: (1) debris flows are the most common in all parts of the fjord - they are often small with a subaerial component where fjord wall slope is very high or tend to exceed volumes of 106 m3 where fjord wall slope is lower, allowing for accumulation of marine sediments; (2) large failures of oversteepened glacial sediments occurring at transgressive moraines and glaciomarine plateaus following deglaciation - the largest is at Squally Channel with an estimated volume of 109 m3; (3) fjord wall failures that involve bedrock slump or rock avalanche; (4) translation of marine sediments; (5) composite/other slides; and (6) two scallop-shaped sackungen, or deep-seated gravitational slope deformations of granodiorite with volumes exceeding 60 × 106 m3. The postglacial marine sedimentary record shows evidence of large-scale slope failures of all styles that were especially active following deglaciation. The Holocene marks a transition to a lower frequency and change to primarily debris flows and smaller rock slides. Slope failures that may be capable of generating tsunamis and may be damaging to coastal infrastructure have occurred in all parts of Douglas Channel through much of the Holocene. Here we present a morphological analysis with volume estimates and age control using multibeam bathymetry, high-resolution sub-bottom data and sediment cores. The study details an extensive analysis of slope failures in a fjord network that can be extended to other fjord environments.
Summary(Plain Language Summary, not published)
This article summarizes over 100 slope failures in the Douglas Channel fjord over the past 10 000 years. We show that the biggest failures happened over a short period of time following deglaciation and that the processes responsible for these large failures have not been active for several thousand years. Modern landslides may be capable of producing dangerous tsunamis and may be a risk to seabed infrastructure. Results are based on an extensive five year field campaign and we discuss how these results can be applied to other fjords in British Columbia and elsewhere in the world.

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