Erosion and soil erosion

Severe soil erosion in the Gina River catchment, Ethiopia
Severe soil erosion in the Gina River catchment, Ethiopia
Image Credit: Rüdiger Hahl 2003
Erosion is a natural process resulting in a levelling of the relief [8].

The intensity of erosion by water is determined by the amount of surface runoff available and the given energy.

Potential Erosion Risk

The processes generating surface runoff determine the potential erosion risk. These processes are dependent on a variety of factors which are interacting in a multidimensional and non-linear relationship [8].

Actual Erosion Risk

Human activities such as agriculture affect erosional processes which are then summed up to soil erosion.

In general, soil erosion shows an increased intensity compared to natural erosion processes. Human impact causes a reduction of natural vegetation cover or even complete destruction [8]. If vegetation is reduced the amount of precipitation which is intercepted and evapotranspirated decreases and no natural barrier holds up the downward moving water. This results in a higher proportion of precipitation which runs unhampered on the surface downslope causing, rill or gully erosion. This is aggravated if the soil is compacted by human and animal activities. Soil compaction reduces the infiltration rate. The splash effect is also higher if the protecting vegetation cover is lacking which causes sheet erosion [9]. Soil erosion risk increases.

However, positive effects can arise from human activities such as practicing soil and water conservation measures [8].

These interactions of land use, vegetation cover and soil erosion risk are important to understand in order to prevent soil erosion and its damaging impacts. These can be found not only in the immediate surrounding (on-site damages) but also in downstream areas of the watershed (off-site damages). This is an important reason for tackling the problems by the Intergated Watershed Management approach.