Control of soil erosion:
The most significant measures of erosion control include (i) growth of grasses, shrubs and trees on soils and (ii) construction of a drainage system which can prevent free, uncontrolled flow of water. Water flow causes formation of narrow channels or gullies andleads to development of deep narrow valleys leading to ravine land. The famous Chambal ravines have been formed as a result of deep soil erosion and the process is still continuing. This can be controlled by constructing a series of check dams which prevent the flow of running water and widening of gullies. Formation of a broad wall of stone along the coasts of Maharashtra, Kerala, Andhra Pradesh and Orissa has proved to be very effective in controlling erosion by sea waves and currents. Movement of sand by gusts of wind in the deserts and sandy coasts can be prevented by putting barriers of trees and shrubs across the path of wind. In the mountain and hilly areas, planting of stems and branches of self propagating trees and shrubs, not only strengthens the slope of the terrace but also provides fuelwood and fodder to the farmers. Alternation of beds of crops with strips of erosion resistant vegetation like grasses, shrubs. trees, maize, sugarcane, cotton and tobacco etc. brings about stabilisation of the terraced fields on mountainous and hilly areas. The most effective step in controlling erosion and mass movement, such as landslides in the hills, is the construction of a network of the drainage ditches which are filled with fragments of stones or bricks so that water flows out through them. The hill slopes are stabilised by constructing walls around them which allows the free passage of water. On the vulnerable slopes, a cover of vegetation is provided and in the beginning, seeds are covered with coir netting pegged firmly to the ground. Netting checks erosion, holds the soil material together and adds nutrients. The quick growth of grass stabilises the soil.