Britannica
Sources used in this answer
How does the steepness of a slope affect the chance of a landslide?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
landslide
This 1995 landslide at La Conchita, a coastal town in California, swept away a hillside road and destroyed a number of houses.
The steepness of a slope is a critical factor in landslide susceptibility because it directly influences the gravitational shear stresses acting on the slope's materials. Landslides occur when these gravitational stresses, along with other forces, exceed the shear strength of the soil, rock, or debris forming the slope.12
The relationship between slope steepness and landslide risk is characterized by the following:
- Oversteepening: Processes such as natural erosion or human-made excavations can oversteepen the base of a slope, increasing the internal shear stress and making the area more prone to failure.2
- Gravity and Movement: On steeper gradients, materials are more susceptible to detachment and downward movement. For example, toppling involves the rotation of material outward from a steep slope face, while falls occur when materials detach from steep slopes and move freely under gravity.2
- Mitigation: Because steepness contributes to instability, one common method for preventing landslides is modifying the slope geometry to reduce the gradient.2