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This is a modified version of Mrs. Beukeboom’s M.Sc. thesis research on:

This is a modified version of Mrs. Beukeboom’s M.Sc. thesis research on: Riverbank Characteristics and Stability along the Upper Estuarine Reaches of the Moose River, Northern Ontario. Department of Land Resource Science University of Guelph September 26, 2000.

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This is a modified version of Mrs. Beukeboom’s M.Sc. thesis research on:

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  1. This is a modified version of Mrs. Beukeboom’s M.Sc. thesis research on: Riverbank Characteristics and Stability along the Upper Estuarine Reaches of the Moose River, Northern Ontario Department of Land Resource Science University of Guelph September 26, 2000

  2. Hudson Bay Lowland - extent of Tyrrell Sea (Martini, 1986)

  3. Goals 1. Determine the factors contributing to bank failure occurrence. • What? • Where? • Why? • When? • How?

  4. Riverbank Stratigraphy silt unit Tyrrell Sea clay unit

  5. Bank Stratigraphy SAND SILT Dunes Laminations Cut and fill structures Blocky structure

  6. WHAT? Examples of Mass Movements Rotational slump Translational slide

  7. Rotational slump curved motion face failure toe failure failure plane base failure Translational slide linear motion failure surface WHAT?

  8. WHAT? Examples of Mass Movements Translational slide Rotational slump Block fall Earth flow

  9. Large rotational slump

  10. WHY? External Factors Erosive River Water litter silt sand ice-rafted cobbles clay Undercutting erosion by high water levels during the spring freshet.

  11. north mainland river flow Ice is forced over the bank crest Bulldozing at the toe of the bank Ice pushes the upper silt unit Scars on tree trunks WHEN? HOW? Erosive River Ice

  12. Summer 1997 Fall 1997 Spring 1998 Well added in Spring 1998 HOW? Seasonal Variation in Water Table Distance from bank crest (m) 0 5 10 15 20 25 30 0 0.5 1.0 Depth (m) 1.5 2.0 2.5 3.0 3.5

  13. HOW? Human Impact Cree Village - retaining wall -Two Bays cruiser Freighter canoes at docks Human activities have some impact on the riverbanks.

  14. HOW? Human Impact - Stability Projects slump Moose River flow direction Store Creek

  15. HOW? Bank Stratigraphy - Tyrrell Sea clay

  16. Slope Stability Model 10 most critical surfaces MINIMUM BISHOP FOS = 1.70 Bank Height (m) water table Width (m)

  17. Slope Stability Model FOS Season Scenario 1.70 1.66 1.80 1.85 1.72 1.73 Spring Summer Autumn May - spring freshet May - undercut May - ice jam Frozen ground August October FOS = Factory of Safety

  18. HOW?Sensitivity of the Tyrrell Sea Clay Sample ID In-situ Strength (kPa) Remoulded Strength (kPa) Sensitivity (S) NML S15 NML S30 NML T2 SPI T8 NML S17 BI T1 BxI T9 13.1 13.1 14.3 28.7 16.9 11.5 30.3 0.7 0.8 0.9 3.6 2.1 1.6 5.3 18.7 16.4 15.9 8.0 8.0 7.2 5.7 • not quick clay (remoulded strength < 0.5 kPa) • range from low (S < 8.0) to medium-high sensitivity (S >8.0)

  19. Scanning Electron Microscopy Tyrrell Sea Clay Marine diatoms – The presence of these diatoms along a fresh water river prove that this clay was deposited under marine conditions. Most quick clays are deposited under marine conditions. Tyrrell Sea Clay Open structure The open structure of this clay is similar to the Leda clay found in Ontario and Quebec. This “card-house” structure is very stable until the bonds that join the edges of the platelets are disturbed (due to flushing out during the spring melt, ice jams, earthquakes etc.)

  20. Conclusions 1. Stratigraphic influence • sand unit on islands aid drainage • undercutting erodes sand - block falls • silt unit of mainland frequently experience rotational slumping particularly in the springduring break up • TSC unit involved in deep rotational slumps and earth flows

  21. Conclusions 2. Subarctic climate • freezing cements sediment together in winter • spring thaw creates wet conditions for bank • river ice is erosive - undercuts, steepens • loss of support as ice jam passes reduces stability

  22. Conclusions 3. Fluvial dynamics of estuary • regular inundation and exposure of TSC  cracks, degrades basal unit • erosive effect positively corresponds withfailure occurrence

  23. Conclusions 4. Human Impact • can facilitate failure  deforestation, drainage, excavation • changing bank morphology by grading

  24. Conclusions 5. Tyrrell Sea clay • medium to high sensitivity • open structure • high primary mineral content • high silt content • low liquid limit • high divalent cation adsorption • low sodium content

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