SQ Summer 2017 Context

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CSL Heron Squamish Operations
April-October 2017

Context w.r.t. decadal fan-delta evolution

John E.Hughes Clarke, Anand Hiroji, Liam Cahill	Ian Church, Angela Gillis
Center for Coastal and Ocean Mapping University of New Hampshire, USA	Ocean Mapping Group University of New Brunswick, Canada

Context within the Full Squamish fan delta system

The focus area is a subset of the whole fan delta. Previous studies (2011,2012,2013,2015) have focused on the proximal region from the flat delta top (~1m below chart datum) to ~ 100m. The South Channel focus is now looking at the newly developed section of channel in the 100-190m depth range. That it turn feeds a distal unchanneled plain that is clearly active from ~ 180 to 220m depth.

The following bathymetric figures show the surveys, from which the difference maps are calculated.

2005 survey CCGS Vector	2015 survey CSL Heron	spring 2016 CCGS Vector	fall 2016 CCGS Vector	spring 2017 CSL Heron	mid summer 2017 CSL Heron

Depth Differences

The full fan activity can be assessed by looking at cumulative change: The following difference maps (all scaled from -4m (black) to +4m white) show the active areas for the past decade and the past 12 months.

2015-2005 10 years of activity	Oct 2016 - June 2016 one summer	April 2017- Oct 2016 one (very active!) winter	June - April 2017 activity so far this year

Fig D1	Fig D2	Fig D3	Fig D4

Fig D1: The decadal time scale picture This shows the switch in the South Channel from an unconstrained lobe to a single channel (happened in the 2009-2011 period). And it also shows the distal extent of resolvable change. From this it is clear that deposition is extending to beyond WoodFibre.

Fig D2: this shows activity in the 2016 summer. As can be clearly seen, the South Channel now dominates all activity. And within a single summer, resolvable change does extend down to just before Woodfibre.

Fig D3: This is the most active overwintering ever recorded. In November and December, British Columbia had one of the highest periods of rainfall. As a result the morphological change over that winter is as significant as the previous summer, with resolvable change again extending toward Woodfibre.

Fig D4: this shows the activity so far this year (May and up to June 12th). As can be seen, the South Channel has been very active. But significantly, so far this year there has NOT been any flows that extends significantly beyond the distal channel mouth onto the unchanneled plain.

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