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Interactions between water, ice and sediment during spring breakup at the mouth of the Mackenzie River, Northwest Territories
Steven M. Solomon1, Donald L. Forbes1, Maxime Belanger2, Dustin Whalen1, Philip
Marsh3
1Geological Survey of Canada, 2University of Alberta, 3Environment Canada
Acknowledgements
Program for Energy Research and Development (PERD)Northern Energy Development MCPolar Continental Shelf ProjectAurora Research InstituteMGMEnergy, Shell Canada, Chevron Canada – logistic support and dataPartners and contractors: University of Calgary, University of Alberta, C-CORE, Aquatics Environmental, Tumichiat OutfittersSatellite imagery- ESA, CSA, University of Alaska – GINACanadian Helicopter Corporation
Issues and Objective
Onshore gas production will lead to offshore exploration and exploitation of known offshore discoveries (pipelines)Assessment of risk to pipelines, navigation channels and infrastructure due to nearshore geohazards
Ice-seabed interaction – scours, shallow subsea permafrostMagnitude, extent and mechanisms of nearshore erosion and deposition
Objective: Document river-mouth processes and river-ocean interactions during spring break-up.
Study Area
Winter-Spring Oceanographic Environment
Freeze-up in mid-late October with formation of landfast and bottom-fast ice.Continuous discharge throughout winterDevelopment of “Lake Herlinveaux” – fresh water ponded behind stamuki(MacDonald and Carmack)Punctuated quiescence beneath winter ice - winter surgesEarly-mid-May: increased river discharge prior to sea ice melt
Suspended sediment concentrations up to 4 g/lSPM load enters fresh water basinSediment may be flocculated (Droppo et al 1998)
Lake Herlinveaux Mackenzie at Arctic Red
River 1974-1983After Hill et al 2001
Fluvial sediment delivery modes
Hyperpycnal flowsRequire > 40 g/l if receiving water is salty, but < 1 g/l if fresh (e.g.Mulderand Syvitski, 1995)Spring freshet TSS > 1g/l) plus ice constrained!
Homopycnal
Hypopycnal
Boggs, S. 1995 Principles of Sedimentology and Stratigraphy, 2nd edition, Prentice Hall
Hyperpycnal
Methods
Synthetic Aperture Radar (SAR) for mapping bottomfast iceMODIS imagery to monitor progression of breakup in near-real timeTime lapse camera – flood elevation and timingWater level gauges – on-ice water levelsHelicopter overflights and on-ice observationsSidescan sonar and depth sounding – strudel scour mapping
Setting the stage: Winter Bottomfast Ice Development
Ice Elevations
( -5.1 to -4.8( -5.4 to -5.1( -5.5 to -5.4( -5.6 to -5.5( -5.8 to -5.6( -6.8 to -5.8
Bottomfast ice controls on overflow and drainage
End of Winter
Early breakup
Mid-breakup
BFI influence on water flow and channel incision
19962005
Nearshore BFI conditions prior to breakup
Spring breakup 2008
May 7, 18, 20, 22, 23, 24, 25, 30, June 4, 7, 11
Discharge and Overflow Timing
Overflow Initiation Overflow Max peak WL Inuvik
07- may-08 21-23- May-08 31- May-08
04-May-07 19-May-07 01-Jun-07
14-May-06 23-May-06 29-May-06
08-May-05 16-May-05 25-May-05
26-May-04 30-May-04 03-Jun-04
08-May-03 17-May-03 04-Jun-03
4-Jun-07
Overflow precedes peak WL by several days to 2 weeks
1-3 Jun-08
Peak WL Outer delta
Overflow – sediment concentration
Overflow waters – variable sediment concentrations
Peak freshet concentration: Lesack data 2007 – peak loads exiting delta in Aug Suspended Sediment 2008
0.0
200.0
400.0
600.0
800.0
1000.0
1200.0
22-Apr-08 12-May-08 1-Jun-08 21-Jun-08 11-Jul-08 31-Jul-08 20-Aug-08 9-Sep-08
Mackenzie at Arc tic Red Middle Channel at Langley (OD) East Channel (OD)
0.0200.0400.0600.0800.0
1000.01200.01400.01600.01800.02000.0
5/3 5/8 5/13 5/18 5/23 5/28 6/2 6/7 6/12 6/17 6/22
Mackenzie at Arctic Red Middle Channel (MD) East Channel (MD)Middle Channel at Langley (OD) Reindeer Channel (OD) Napoiak Channel (OD)West Channel (OD) East Channel (OD) Arctic Red RiverPeel River Peel Channel (MD)
Initiation of Breakup Rising limb of the spring freshet
Increased discharge from southern drainage basinsInitiation of overflow, backwater effectsIncreased current velocity in ice-constrained channels?
May 7, 2008May 18, 2008May 22, 2008
Local backwater effects?
Coastal well-site K30 looking north
May 21 Backwater flooding
June 3 Freshet Peak
May 18
May 31
Overflow water levels over ice
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
26-Apr 03-May 10-May 17-May 24-May 31-May 07-Jun 14-Jun
BH4depth_corr Strudel_depth_corr Tuk_WL_24hMA
Overflow and upwelling May 21-22, 2008
Strudel Drainage
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f
ffff
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g
gg
ggggggggggg
gggggg
g
ggg
gl
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0 5
kilometres
10
Strudel Scours
Summary and Conclusions
Upwelling, overflow and strudel drainageenergetic but short-lived processes precede peak discharge by several days to two weekslocations are controlled by the distribution of BFI
Backwater flooding and overflow are indicators of ice-constraints at distributary mouths
Timing of overflow drainage indicates removal of constraints prior to peak discharge Flow perturbations at constraints are unknown
Strudel scour is extensivelocations appear to be predictableInfill may occur within a single season
Future: What is happening to the dirt?Erosion at ice-constrained channel mouths Behaviour of suspended materials in plumePhysical modelling of strudel drainage