scalloped edge of the
intertidal shoal south of the navigation beacon.
This is the main area of encroachment into the berth 2 dredged basin (otter for scale). |
Squamish
Terminals Berth Encroachment Assessment of the 2006-2012 changes in the dredged basin John E. Hughes Clarke Ocean Mapping Group Dept. Geodesy and Geomatics Engineering University of New Brunswick March 2013 |
Executive Summary The BC Coast Pilots have recently expressed concerned about the extent of siltation in the Squamish Terminals berthing areas, particularly the region immediately adjacent to the actively growing Squamish Delta. This report is a compilation of the pertinent UNB survey data at the request of CHS Pacific (Peter Wills). UNB has been actively surveying the Squamish Delta front for the past two years. Based on this analysis, it is clear that, from 2006 to 2012, the lip of the delta, immediately adjacent to Berth 2 of Squamish Terminals has prograded into the dredged basin by ~ 20m. At this point the entrance to the berth is only 140m wide (as defined by the 5m contours). This process appears to be accelerating as the main river channel mouth has now split off and formed a secondary channel that feeds to the east directly into the dredged basin. |
Fig. 1: overview of
encroachment.
|
Squamish Terminals facilities |
Prograding and Avulsing Delta
Front adjacent to Berth 2. |
April 2007 |
January 2011 |
November 2012 |
CSS Otter Bay EM3002 survey performed
by CHS Pacific (Czotter and Lessels) RTK GPS for horizontal control. Reduced using observed tides at Squamish. |
CSL Heron EM710 survey performed by
OMG/UNB RTG-GPS for horizontal control. Reduced to CD using Point Atkinson predicted. |
CSL Heron EM710 survey performed by
OMG/UNB. RTG-GPS for horizontal control. Reduced to CD using Squamish predicted. |
ESRI binary grid file flt - hdr |
ESRI binary grid file flt - hdr |
ESRI binary grid file flt - hdr |
CHS Chart 3534 (2010 vintage) |
Spring 2006 |
Spring 2007 |
This shows the charted 5m
contour and the comparison to the spring 2006 multibeam
rendition of that contour. Note that the chart records
a greater progradation of the delta lip than seen in the
multibeam. |
This is the spring 2006 survey
which is the first multibeam rendition of the delta lip.
This represents the furthest south extension of the delta
lip recorded thus far by multibeam. Note that the drying
line was not investigated due to draught clearance concerns. |
This is the spring 2007 survey.
Over the summer of 2006 the delta lip collapsed resulting in
a >100m retreat of the 5m contour. By the end of the 2007
summer, much of that retreat had been reacquired by delta
lip advance. Note that in one year, the flank of the delta by the navigational beacon had advanced by a few metres. |
January 2011 | JD168 2011 | JD234 2011 |
This was in late January at a very low
discharge period. It represents the most extensive survey
done of the intertidal shoal. This reveals that there was a localized dredging effort immediately seaward of the 5m contour where it encroaches on the berth. From this, one can see ~15m of progradation of the delta lip by the beacon since 2006 |
This was in mid summer when the river was
very active. This was the first time that the avulsion
channel was surveyed. |
This was in mid August when the river was
slowing down (although a surge occurred on this day). This
is the last record of the channel in this year. Note than over the 2011 summer the delta lip off the avulsed channel mouth has prograded more rapidly than off the beacon. |
JD183 2012 | JD268 2012 | JD331 2012 |
This was the only time we examined the
avulsion channel in 2012. This was during the active summer
period. As can be seen, the 5m contour has now prograded ~ 10m out into the dredged basin. Slightly more than in 2011 (~7m then) |
This was in September after the river level
had dropped. No significant activity, as can be noted from
the lack of river floor bedforms. |
This was in late November just after the
autumn storms. The delta front had changed significantly,
but the flank of the delta appears the same. |