7- Slope Failure


Slope failures are downhill movements of rock, soil, regolith or some combination of these. Regolith is a term we have not used before but it is the best term to describe any weathered bedrock, or non-cemented sedimentary deposits of gravel sand silt or clay above the solid bedrock but below the soil. A lot of factors play a part in slope failure and usually a combination of more than one eventually causes the event; for instance, improper construction on a steep slope, followed by heavy rainfall.  Although in this case heavy rain triggered the event, other factors played a part in destabilizing the slope as well.

Learning Objectives

Upon completion of this unit you should be able to:

1. Explain the process of soil creep and the evidence left on the landscape.
2.  Describe the driving mass and the resisting mass of a failure-prone slope and how slope modifications can change the balance between the two.
3.  Describe the ways in which terraces can both increase and decrease the stability of a slope.
4.  Explain why different sediment and rocktypes can either increase or decrease the stability of a slope.
5.  Explain liquefaction and give some good examples of the sediments and conditions under which it is likely to happen.
6.  List the various different types of mechanical weathering that can decrease slope stability.
7.  Explain how excess water can lead to the destabilization of slopes and under which conditions this is likely to happen.
8.  Discuss the formation of the Scarborough Bluffs and explain the various properties that make the slopes failure-prone.
9.  Explain how vegetation can increase or decrease the stability of slopes.
10. Differentiate between types of slope failure.
11. Classify flows based on their speed and the amount of water they contain.
12. Discuss underwater slope failures and understand the impacts they can have on surrounding coastlines.
13. Know the ways in which we can reduce loss of life by slope failure through predictive and preventive measures.

 Required Reading

Abbott, P.L., 2014. Natural Disasters, Ninth Edition: Readings From the Old Book

Abbott, P.L., 2012. Natural Disasters, Eighth Edition:

Glossary Terms

Bottomset Beds Limestone
Canopy Liquefaction
Chemical Weathering Loess
Clearcut Mudflow
Creep Ottawa-St. Lawrence Graben
Delta Paleozoic
Epicentre Piping
Evapotranspiration Quick Clay
Exfoliation Rip-Rap
Flash Floods Root Wedging
Foreset Beds Scarborough Bluffs
Freeze-Thaw Shale
Glacial Till Solifluction Lobe
Grand Banks Talus
Granite Terrace
Gravity Thermal Expansion
Intraplate Earthquake Tile Drain
Lahar Turbidity Current