Question

Write five causes of soil erosion.

Answer 1

1 deforestation

2 flash floods

3 over grazing

4 extensive farming

5 mining

Answer 2

Rainfall and Flooding

Greater duration and intensity of rainstorm means greater potential for soil erosion. Rainstorm produces four major types of soil erosion including rill erosion, gully erosion, sheet erosion, and splash erosion. These types of erosions are caused by the impacts of raindrops on the soil surface that break down and disperse the soil particles, which are then washed away by the stormwater runoff.

Over time, repeated rainfall can lead to significant amounts of soil loss. Rapidly moving stormwater, flashfloods, and flooding may also occur because of excess surface water runoff, thus, causing extreme local erosion by plucking bed rocks, forming rock cut-basins, creating potholes, and washing away the loosened soil particles.

Rivers and Streams

The flow of rivers and streams causes valley erosion. The water flowing in the rivers and streams tend to eat away the soils along the water systems leading to a V-shaped erosive activity. When the rivers and streams are full of soil deposits due to sedimentation and the valley levels up with the surface, the water ways begin to wash away the soils at the banks.

This erosive activity is termed as lateral erosion which extends the valley floor and brings about a narrow floodplain. This erosive activity is evident in most rivers or streams especially during heavy rainfall and rapid river channel movement.

High Winds

High winds can contribute to soil erosion, particularly in dry weather periods or in the arid and semi-arid (ASAL) regions. The wind picks up the loose soil particles with its natural force and carries them away to far lands, leaving the soil sculptured and denudated. It is severe during the times of drought in the ASAL regions. Hence, wind erosion is a major source of soil degradation and desertification.

Overgrazing, Overstocking and Tillage Practices

The transformation of natural ecosystems to pasture lands has largely contributed to increased rates of soil erosion and the loss of soil nutrients and the top soil. Overstocking and overgrazing has led to reduced ground cover and break down of the soil particles, giving room for erosion and accelerating the erosive effects by wind and rain. This reduces soil quality and agricultural productivity.

Agricultural tillage depending on the machinery used also breaks down the soil particles, making the soils vulnerable to erosion by water. Up and down field tillage practices as well create pathways for surface water runoff and can speed up the soil erosion process.

Deforestation, Reduced Vegetation Cover, and Urbanization

Deforestation and urbanization destroy the vegetation land cover. Agricultural practices such as burning and clearing of vegetation also reduce the overall vegetation cover. As a result, the lack of land cover causes increased rates of soil erosion.