First Documented Large Failure At the Fraser River Delta Front, British Columbia

McKenna, Gord; Luternauer, J L

doi:10.4095/122562

Cited by 10 publications

(7 citation statements)

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“…Vol. 34, 1997 436 elsewhere (McKenna andLuternauer, 1987). Other papers review potential trigger mechanisms in the river mouth region, involving a combination of rapid deposition, high static shear stress, gas compressibility effects, and tidal drawdown (Chillarige et al 1994;Christian et al 1996;Christian and Woeller 1996).…”

Section: River Mouth Flow Slides and Associated Submarine Canyonsmentioning

confidence: 94%

Geomorphology and potential slope instability on the Fraser River delta foreslope, Vancouver, British Columbia

Christian¹,

Mosher²,

Mulder³

et al. 1997

Can. Geotech. J.

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The Fraser River delta lies in one of the highest-risk earthquake regions in Canada and is composed largely of loose fluvial sands, widely recognized as possessing a high seismic liquefaction potential. Recent investigations of the western margin of the Fraser delta indicate that cyclic liquefaction during a large earthquake is possible, potentially giving rise to deformations including lateral spreading, cyclic softening, and possibly flow sliding. A preliminary evaluation of postshaking static slope stability is reported, wherein analyses were constrained by estimated ultimate or steady-state shear strengths inferred from correlations with field data and by shear stresses calculated from existing seabed bathymetry. The resulting postliquefaction factor of safety against sliding was found to be less than unity for upper Roberts Bank slope, assuming a low bound ultimate shear strength equivalent to 0.06 P o ′. Insufficient data exists to fully evaluate the validity of this assumption; however, extensive failure deposits exist along the base of the delta slope.Résumé : Le delta du fleuve Fraser est localisé dans une des régions ayant les plus hauts risques sismiques au Canada et comprend pour une bonne part des sables fluviaux meubles, très connus comme possédant un potentiel élevé de liquéfaction sismique. Des études récentes de la rive ouest du delta du Fraser indiquent que la liquéfaction cyclique durant un fort tremblement de terre est possible, engendrant potentiellement des déformations incluant des extensions latérales, un ramollissement cyclique et possiblement une coulée. L'on présente une évaluation préliminaire de la stabilité statique des pentes après secousse, dans laquelle les analyses ont été limitées aux valeurs estimées des résistances au cisaillement ultimes ou à l'état d'équilibre déduites de corrélations avec les donnnées du terrain, et aux contraintes de cisaillement calculées en partant de la bathymétrie du lit de mer existant. L'on a trouvé que le coefficient postliquéfaction de sécurité contre le glissement était inférieur à l'unité pour la pente de la terrasse supérieure Roberts, en supposant une limite inférieure de résistance au cisaillement ultime équivalente a 0,06 P o ′. Les données pour évaluer la validité de cette hypothèse sont insuffisantes, cependant, il y a abondance de dépôts de rupture le long de la base de la pente du delta.

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Section: River Mouth Flow Slides and Associated Submarine Canyonsmentioning

confidence: 94%

Geomorphology and potential slope instability on the Fraser River delta foreslope, Vancouver, British Columbia

Christian¹,

Mosher²,

Mulder³

et al. 1997

Can. Geotech. J.

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“…Such high rates of accumulation create unstable conditions at the top of the slope and slope failures are known to occur on an inter-annual time scale (McKenna and Luternauer, 1987;McKenna et al, 1992). These slope failures probably initiate by liquefaction and are transformed into turbidity currents as they flow down the steep slope.…”

Section: Gravity Flowsmentioning

confidence: 98%

Sedimentary processes and sediment dispersal in the southern Strait of Georgia, BC, Canada

Hill

Conway

Lintern

et al. 2008

Marine Environmental Research

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This paper presents a review of sediment dispersal processes in the Strait of Georgia, based on marine geological studies. Sediment from the Fraser River is dispersed around the Strait through a variety of transport pathways. Most sand and coarser silt fractions settle out and are deposited within a few 100 m of the channel mouths. Both channelled and non-channelled gravity flows probably transport sediment downslope and onto the basin floor. Asymmetric tidal currents force a predominantly northward sediment drift, resulting in a reworked slope off Roberts Bank and a finer-grained depositional slope off Sturgeon Bank. Far-field sediment accumulation is controlled by local morphology and sediment dynamics. Multibeam mapping and seismic profiling reveal that some parts of the basin floor are characterized by bottom sediment reworking and erosion. Given the complexities of sediment dispersal and seafloor reworking, generalizations about sediment dispersal paths and sedimentation rates are difficult. Future understanding will be advanced by the cabled observatory, VENUS, which will enable near real-time monitoring of key processes.

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“…Mass movements down these gullies redistribute deposits on the delta slope and locally deform the foreslope sediments (Luternauer and Finn 1983;McKenna and Luternauer 1987).…”

Section: Foreslopementioning

confidence: 99%

Holocene sea-level change and delta growth: Fraser River delta, British Columbia

Williams¹,

Roberts²

1989

Can. J. Earth Sci.

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The Fraser River has been building its delta into the Strait of Georgia in southwestern British Columbia for about the last 9000 years. This period encompassed a relative sea-level rise of some 13 m. This study concerns the effects of the rise in sea level on the depositional evolution of the delta.The lithostratigraphy of the delta was established by a series of drill cores. Four major lithostratigraphic units were defined: peat, organic-rich silt, interbedded silts and sands, and massive sands. These units were interpreted in terms of the delta's contemporary depositional environments, including peat bog, floodplain, and intertidal zone.Analysis of the d e b ' s depositional architecture and chronology indicates that the delta continued to prograde during the rise in sea level. A marine transgression, accompanied by the landward migration of marine and intertidal facies, did not occur. Growth of the delta during the rise in sea level was accomplished by both vertical accretion and lateral progradation.Vertical-accretion rates during the rise in sea-level averaged 2.4 mmlyear and ranged up to about 5.3 mrnlyear. Lateral progradation of the delta was most rapid in the early stages of growth (9000-8000 years ago), when the average rate was 6.5 &year, and slowest during the period of most rapid sea-level rise, when the rate declined to less than 1 mlyear. The progradation rate of 2.4 &year calculated for the most recent period (2250-present) compares well with estimates based on bathymetric surveys.A revised sea-level curve for the Fraser Lowland region is proposed on the basis of the identification of former sea-level positions in core at the lithologic transitions from tidal-marsh to intertidal deposits. The curve contains a hitherto unknown stillstand that occurred ca 6000 years ago and shows that the mid-Holocene sea-level rise continued until about 2250 years ago.La rivibre Fraser construit so; delta 2 l'intkrieur du dttroit de Georgia, dans le sud-ouest de la Colombie-Britannique, depuis plus ou moins 9000 ans. Durant ce temps, le niveau de la rner relatif s'est BlevC approximativement de 13 m. La prCsente Ctude trait des effets de 1'ClCvation du niveau de la rner sur 1'Cvolution dtp6ts dans le delta.La lithostratigraphie du delta a 6tt ttablie par 1'Ctude d'une sCrie de carottes de forage. Quatre unitts lithostratigraphiques ont t t t dtfinies : tourbe, silt riche en rnatikre organique, silts et sables interstratifies et sables massifs. Ces unites ont Bt C interprktks en termes des milieux de dCp6ts deltaiques contemporains, incluant tourbibre, plaine d'inondation et zone intertidale.L'analyse de l'architecture des dCp6ts deltaiques et de leur chronologie r6vkle une progradation continue du delta durant la ptriode d'tltvation du niveau de la mer. ll n'y a pas eu de transgression marine qui aurait pu accompagner une migration vers les terres de facibs marins et inter-tidaux. La croissance du delta durant la pCriode d'tlkvation du niveau de la mer fut le rtsultat d'une accrCtion verticale et d'une progradation...

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First Documented Large Failure At the Fraser River Delta Front, British Columbia

Cited by 10 publications

References 0 publications

Geomorphology and potential slope instability on the Fraser River delta foreslope, Vancouver, British Columbia

Geomorphology and potential slope instability on the Fraser River delta foreslope, Vancouver, British Columbia

Sedimentary processes and sediment dispersal in the southern Strait of Georgia, BC, Canada

Holocene sea-level change and delta growth: Fraser River delta, British Columbia

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