Imaging active mass-wasting and sediment flows on a fjord delta, Squamish, British Columbia

John E. Hughes Clarke*, Carlos R. Vidiera Marques, Danar Pratomo

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

52 Citations (Scopus)

Abstract

An active fjord head delta in Squamish British Columbia, was selected as the location for a repetitive multibeam survey program to monitor temporal evolution of the prodelta morphology. Daily resurveys in 2011 established the style and extent of submarine mass movements, their typical periodicity and the conditions associated with the most active periods. This has now been followed by an hourly resurvey program in 2012 during those most active periods to actually witness the progression of activity immediately preceding, during and subsequent to a singular event. The delta front in depths of 20–50 m is often the apparent start point for trains of sequential erosive and depositional events associated with upslope bedform migration along prodelta channels. Heavy targets on the channel floors were monitored in 2011 and indicated rare, abrupt down channel displacements of a few hundred metres, indicating that a small subset of events involved bulk translation of the seabed. In 2011, a bottom-mounted ADCP beyond one channel mouth recorded clear turbidity current events for a subset of the channel bedform migration periods. In 2012, using multibeam water column imaging and a rapidly dipping towed optical backscatter probe, the evolution of a descending suspended sediment plume below the overlying river plume was monitored on an hourly basis. Towards low water, that descending plume was seen to occasionally feed a near seabed higher suspended sediment layer. On the development of this layer, the water column imaging revealed a thin basal flow that lasted about an hour and corresponded directly with the period ofmigration of the channel floor bedforms.Delta-lip failures are associated with the upslope end of about half of the bedform trains suggesting an alternate initiating mechanism.

Original languageEnglish
Title of host publicationAdvances in Natural and Technological Hazards Research
PublisherSpringer Netherlands
Pages249-260
Number of pages12
DOIs
Publication statusPublished - 2014
Externally publishedYes

Publication series

NameAdvances in Natural and Technological Hazards Research
Volume37
ISSN (Print)1878-9897
ISSN (Electronic)2213-6959

Keywords

  • Bedform translation
  • Cyclic steps
  • Prodelta mass wasting
  • Surface differences
  • Turbidity current
  • Water column imaging

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