Any one factor cannot be considered responsible for landslide, but many joint factors cause landslides.
The responsible factors for landslide or mudslide can be divided into two categories: 1
. Natural factors
2. Man – made factors.
1. Natural factors: Structure of rocks, slope of land, folding and prolapse in rocks, amount of rainfall, vegetation cover, etc. are some factors responsible for landslides. Weathering is the natural procedure of rock deterioration that leads to weak, landslide suspective materials. Erosion caused by sporadic water such as streams, rivers, wind, currents, ice and waves wipes out latent and lateral slope support, enabling landslides to occur easily.
Most of the events of landslides take place in newly-folded mountaining regions as the process of rising of mountains goes on continuously. Because, in this process, edges of rocks become weaker and there is sharp slope. In these conditions, high amount of rainfall works as lubricant for landslide, and from the weaker joints, rocks start to slope downwards, and if it is heavy rainfall, they come down with a noise of thunder.
Earth’s gravitational force also helps in this process. With sharp slope, gravitational force also increases. Rapid landslides occur in the slopes of more than 45°. That is why, there are a number of events of landslides during the rainy season on Konkan railway route in the Western Ghats. In the mountains, rivers cause land erosion. In mountainous regions, rivers cut the base of the lands and the mountains, and hence, events of landslides occur.
2. Man – made factors: Natural disasters like landslides have increased in number due to insensible development done by mankind; forests have been over – exploited for obtaining paper, wood and timber. Due to deforestration, roots of trees loose their grasp over the soil as well as on land.
Man – induced landslides may result from changes in slope caused by terracing for agriculture, cut and fill construction for highways, construction activities, mining operations, rapid draw-down of the dams, and changes in irrigation or surface run – off.
