1. Department of Land Resource Science
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
INTRODUCTION
Hudson Bay Lowland
Two towns: Moosonee and Moose Factory
The upper estuarine reaches of the Moose River suffer continual degradation.
Riverbank instability threatens homes, roads, docks and boats
Department of Land Resource Science
University of Guelph
September 26, 2000

2. Hudson Bay Lowland - extent of Tyrrell Sea
BACKGROUND
isostatically rebounding for the last years
(Martini, 1986)

3. Goals What? Where? Why? When? How?
1. Determine the factors contributing to bank failure occurrence.
What?
Where?
Why?
When?
How?
What are the types of mass movements
Where are they occuring - specific localities? Random?
Why are they occuring in those localities?
When do they occur?
How are the riverbanks effected?

4. Riverbank Stratigraphy
silt unit
Stratigraphy consists of a basal clay unit, overlain by sand and/or silt units with local gravel components.
Basal unit is a glaciomarine deposit from the Tyrrell Sea that once covered the Hudson Bay Lowland
Deposit is comparable to the Champlain Sea clay which is responsible for landslides
Tyrrell Sea clay unit

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

6. Examples of Mass Movements
WHAT?
Examples of Mass Movements
Rotational slump
Translational slide
Landslides - generic term for mass movement
landslides in news in Ottawa - mostly rotational slumping
landslides in this area - mostly rotational slumping

7. WHAT? Rotational slump Translational slide curved motion failure plane
base failure
face failure
toe failure
Rotational slump
failure plane
failure surface
linear motion
Translational slide
Rotational slump - displacement along a curved plane
Different depths
Common on the north mainland
common was toe failure - clay unit
face - silt
Translational slide - displacement along a linear plane
Steep, cohesionless slopes
Banks of Haysey suitable conditions

8. Examples of Mass Movements
WHAT?
Examples of Mass Movements
Rotational slump
Translational slide
Block fall - detachment and fall due to gravity
Undercut sand unit - silt block drops
On the island
Earth Flow - saturated teardrop-shaped mass that flows
Saturated clay conditions
Saturated sand conditions (actually seen)
Earth flow
Block fall

9. Large rotational slump
6.5 m high
54 m wide x 73 m long
Dad, my field assistant

10. WHY? External Factors Erosive River Water
litter
silt
sand
ice-rafted
cobbles
discharge peaks during spring freshet
erosion of top of bank
ledge in clay marking high water level
ice rafted cobbles
clay
Undercutting erosion by high water levels during the spring freshet.

11. WHEN? Erosive River Ice HOW? Ice is forced over the bank crest
north mainland
river flow
Ice is forced over the bank crest
Bulldozing at the toe of the bank
Scars on tree trunks
Ice pushes the upper silt unit
for 6 months of the year- freeze up in early November, break up end of April
cover with up to 1 m of ice
HOW
oversteeping
instability

12. HOW? Seasonal Variation in Water Table Distance from bank crest (m)5 10 15 20 25 30
0.5
Summer
1997
1.0
Fall 1997
Depth (m)
1.5
Spring
1998
2.0
Well
added in
Spring
1998
2.5
Results - Bank Hydrology Conditions
Data collected Summer 1997, Autumn 1997, Spring 1998
Strong variation between summer and spring conditions
dry banks in the autumn - expereince freezing
recharge in the spring
3.0
3.5

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

14. Human Impact - Stability Projects
HOW?
Human Impact - Stability Projects
slump
Moose River flow direction
Store Creek
successful for this bank, not the other
human activities promote undercutting using the boats, but implementing projects themselves my promote failure occurrence

15. HOW?
Bank Stratigraphy - Tyrrell Sea clay

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

17. Slope Stability Model Season Scenario FOS Spring Summer Autumn
May - spring freshet
May - undercut
May - ice jam
Frozen ground
August
October
1.70
1.66
1.80
1.85
1.72
1.73
minimum FOS = 1.5 for infrastructure
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
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
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 spring during 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 with failure occurrence

23. Conclusions 4. Human Impact can facilitate failure
 deforestation, drainage, excavation
changing bank morphology by grading
is considered important given the location of the failures relative to the human activities of the towns
not necessary km upstream

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