MEANING OF SOIL EROSION
Soil erosion is the process by which the topsoil is detached and carried away by various agents such as water and wind, at the rate that is faster than it is being replaced by soil-forming processes
Soil erosion is a serious problem that has many effects on both the physical and human environment.
EFFECTS OF SOIL EROSION
Soil erosion leads to the loss of productive topsoil forever and only unproductive stony soil is left behind.
This lowers the agricultural productivity of the land.
For example, a large part of the Dodoma region in Tanzania has become unproductive due to severe soil erosion that has occurred there.
The soil left behind after the erosion is thin and cannot hold plants firmly in the ground. The plants are easily uprooted and blown away by the wind. They could also be washed away are buried in the deposited soil.
Structures such as buildings and bridges may be destroyed as a result of erosion. This happens when the surrounding soil is eroded thus weakening their foundation.
When gullies are deepened up to or near the water table underground water is exposed. Some of it evaporates and others flow away. This causes the water table to be lowered. As the resulting plant with shorter roots cannot survive as they are unable to reach the water.
Sand which is eroded from the steep slopes is deposited on the riverbed from which it is scooped for construction purposes this is very common in Tanzania.
Sediments that are carried into rivers, lakes, and oceans may contain chemical pollutants from farms and dumping grounds. These pollutants may kill aquatic life such as fish, coral polyps, and plants. The water may also become unfit for human and animals consumption.
In addition, excessive sedimentation in mangrove swamps may destroy mangrove vegetation.
Soil erosion also causes a water reservoir that has been constructed along some rivers to be filled up with soil sediments. As the result, their lifespan and usefulness are greatly reduced.
Similarly, increased alluvial deposits on the riverbed make the river channel to become shallow which results in frequent flooding.
Last but not least, the continued loss of soil through wind and water erosion leads to the destruction of vegetation cover. This may eventually turn the affected area into a semi-desert region and finally into the desert. This effect can be seen in the central part of Tanzania
MEASURES TO COMBAT SOIL EROSION PROBLEM
- Afforestation and reforestation
- Practicing of good farming method like contour farming
- Reducing the number of livestock to reduce overgrazing
- Education to the public on effect of soil erosion.
- Enacting strict laws which prohibit rampant deforestation
FACTORS INFLUENCING THE RATE OF SOIL EROSION
- The amount and intensity of rainfall.
- The slope of the land.
- The type of soil whereby sand erodes quickly while the clay is resistant to soil erosion.
- Soil depth whereby shallow soil become saturated quickly and are easily eroded than deep soil.
- Vegetation cover.
- Farming methods. Farming methods such as farming along the slope and monoculture make the soil more susceptible to soil erosion.