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TitleFrequency and distribution of shallow hazards that affect the Beaufort Sea potential pipeline area
AuthorWhalen, DORCID logo; Solomon, S; Forbes, D; Beaver, D; Nelson, A; Travaglini, P
Source35th Annual Yellowknife Geoscience Forum abstracts; by Cairns, S; Falck, H; Northwest Territories Geoscience Office, Yellowknife Geoscience Forum Abstracts Volume 2007, 2007. Open Access logo Open Access
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20070424
MeetingNWT Geoscience Forum 2007; Yellowknife, NWT; CA; November 20-22, 2007
Documentcomputer file
Mediaon-line; digital
File formatpdf
ProvinceNorthern offshore region
NTS107C; 117D
AreaMackenzie Delta; Beaufort Sea
Lat/Long WENS-140.0000 -132.0000 70.0000 69.0000
Subjectsmarine geology; sedimentology; ice scours; scouring; scour marks; pipelines; Quaternary
ProgramClimate Change Geoscience Coastal Infrastructure
Released2007 01 01
AbstractA better understanding of seabed morphology in the shallow regions of the Beaufort Sea is essential to provide proper understanding of the geohazards that are created from the progression of ice during freeze and break up periods. This involves repetitive surveys to improve our understanding about the environments through which oil wells will be drilled, dredging and pipeline installation will take place. Work by the Geological Survey of Canada has focused on the low sloping shallow nearshore region of the Mackenzie Delta (>6 m water depth) that extends ~50 km offshore. The potential for significant impacts on subsea pipeline infrastructure is the greatest in this region. High resolution sidescan sonar and multibeam bathymetry systems were used to map the seabed over three consecutive years. The most dominant hazard in the survey area is the scouring of the seabed by the movement of ice during freeze and break up periods. From the 600 plus ice keel scours that were mapped using 2006/2007 high resolution multibeam data it is clear that there is a progressive increase in ice keel scour density offshore. Predominantly scours were sinuous along an SE-NW orientation. The maximum depth measured was 1.2 m with an average scour depth of 0.2 m across the dataset. Evidence of sedimentation is low as scours tended to re-occur throughout the two year period with very little new scours being identified. Not as dominant but potentially a lot more destructive to pipeline installations strudel scour have also been identified for the first time this past field season. Although common in other small deltas on the Alaska and Yukon coast up until now these features have never been documented in the Mackenzie Delta area. A strudel scour is caused when fresh water collecting on top of an ice sheet from flowing rivers during Spring break up drain through a hole in the ice. The effect of the draining water on the shallow ocean floor below forms a near circular depression which is called a strudel scour. Reconnaissance surveys during the 2007 Spring break up identified a number of possible strudel scour locations at the boundary between the bottom fast and floating ice surfaces. A total of three strudel scours were later identified using the high resolution sonar equipment in 1.2 m of water. The largest scour was 20 m wide with a maximum depth of 0.8 m below the surrounding seabed. This discovery has led to a number of questions concerning the frequency, distribution and infill potential of these scours. Future work will look at sediment transport in the area and the affect on the longevity of the strudel scour over months and even years. Although a lot of questions still remain, these data provide a good baseline for assessing the hazard potential on future development in the area.

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