What causes Landslides?

Types of Landslides

Types of Landslides
Reproduced with the permission of the British
Columbia Geological Survey

In general, the factors which influence whether a landslide will occur typically include slope angle, climate, weathering, water content, vegetation, overloading, geology, and slope stability.
How these factors interrelate is important in understanding what causes landslides along with an understanding of the impact humans have on these factors by altering natural processes.
Typically, a number of elements will contribute to a landslide, but often there is one which triggers the movement of material.

Natural causes include:

  • elevation of pore water pressure by saturation of slope material from either intense or prolonged rainfall and seepage
  • vibrations caused by earthquakes
  • undercutting of cliffs and banks by waves or river erosion
  • volcanic eruptions.

Human causes include:

  • removal of vegetation
  • interference with, or changes to, natural drainage
  • leaking pipes such as water and sewer reticulation
  • modification of slopes by construction of roads, railways, buildings, etc
  • overloading slopes
  • mining and quarrying activities
  • vibrations from heavy traffic, blasting, etc
  • excavation or displacement of rocks.

It is important for engineers and geologists to evaluate slope stability and any landslide threat during development assessments so that effective and timely remedial measures can be implemented.