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

Hudson Bay Lowland - extent of Tyrrell Sea BACKGROUND isostatically rebounding for the last 8 000 years (Martini, 1986)

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?

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

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

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

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

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

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

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.

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

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

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.

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

HOW? Bank Stratigraphy - Tyrrell Sea clay

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

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

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)

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.)

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

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

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

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 - 2.5 km upstream

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