A landslide occurs when part of a natural slope is unstable and unable to support its own weight. If a slippery material is present below soil then soil can become heavy with rainwater and prone to landslide. It is a downward or outward movement of soil, rock or vegetation due to gravitational force. This movement can be fall, flow, slide, spread or topple. Landslides occur usually at steep slopes but these may occur in areas with low slope gradient. These may occur due to:
1. Weakness in the composition, material or geological structure of rock or soil formation.
2. External factors, which affect the ground water regimes such as heavy rain, snowmelt, changes in ground water level etc.
3. Creation of new site conditions such as changes to natural slope due to construction activities.