Soil erosion is the washing away of the topsoil from one place to another by erosional agents like wind, water, animals, and glaciers. It takes place in both dry and wet areas.
The wet areas include; the shores of Lake Victoria, Kigezi highlands, Nyanza province, Imatong hills in southern Tanzania.
The dry areas include; Karamoja in North Eastern Uganda, Ankole-Masaka Corridor, Masai land, Turkana Land and Machakos district in Kenya, Kondoa region (Miombo woodlands) in Tanzania.
Running water is the most common agent of soil erosion in East Africa.
Glacial erosion is common in snow-capped mountains e.g. Mt. Kenya, Rwenzori, and Kilimanjaro.
Wind erosion is most common in the dry areas like Karamoja and Turkana land
Types of soil erosion
- Rill erosion: This is the removal of top soil by water leading to the formation of small channels called rills.
- Sheet erosion: This is the uniform removal of top soil over a large area especially from the sloping land as a result of over flow of water. This type of erosion is difficult to notice or detect because of uniformity.
- Gulley erosion: This occurs when the rills are deepened by water to form depressions called gulleys.
- Splash erosion: This occurs from the impact of raindrops hitting the earth surface and the soil particles are splashed to different directions leaving behind small depressions.
- Wind erosion: This is the removal of top soil by wind and in most cases its the lighter particles which are eroded. This type of erosion is common in dry areas and in areas with little or no vegetation.
CAUSES OF SOIL EROSION
- Over grazing: This is common in savannah and semi-arid areas of East Africa where pastoralists keep large numbers of animals e.g. Masai land, Turkana land and Karamoja. The animals especially goats eat up all the grass and leave the ground bare and exposed to agents of erosion like torrential rainfall.
- Industrialization and mining: these activities lead to the breakdown of soil during extraction of minerals and construction of buildings and when it rains heavily, the soils are easily washed away.
- Deforestation: here, the trees are cut down and the soil is exposed to agents like rain water and wind which easily carry away the soil particles.
- Monoculture: when one crop is grown season after season, this leads to soil exhaustion which loosens up the soil hence making the soil particles to be easily eroded.
- Heavy rainfall of over 1500 mm per annum leads to serious surface water runoff which easily erodes the soil from one place to another.
- Bush burning: This is commonly practiced by pastoralists when they are expecting rain which brings new pasture with it. It leaves the ground bare hence exposing it to erosional agents like surface runoff and strong winds.
- Over population: This leads to increased pressure on land through deforestation, monoculture and land fragmentation which are responsible for exposing the soil to agents of erosion like running water.
- Cultivating up and down slope: This loosens the soil particles making them to be easily eroded by runoff.
- Steep relief: this also leads to soil erosion due to downward movement of soil as a result of gravitational pull.