Soil Erosion and Sedimentation

Erosion or to be more specific, soil erosion, is the gradual wearing away of soil particles from natural processes such as wind, water and other elements. This also includes rocks and other geological materials.

Sedimentation is the means by which these broken down particles are then situated in either land or water based environments. They form a large mass comprised or inorganic (or organic materials) and can have a dramatic impact on the environment.

Sediment is transported by natural processes although the volume or 'load' is often increased as a result of man-made interventions such as construction work.

Natural erosion

The Earth is continually being eroded as a result of natural processes such as water flow which help to reshape the landscape. Examples of these include the erosion of old landforms caused by the power of the tides and the creation of new landmasses by sediment load.

Wind

The wind blows sediment particles across continents and oceans. These particles are driven across vast expanses of land where they settle and alter the shape of the area, for example shorelines or agricultural regions.

Ice

A glacier is able to trigger a long process of erosion which occurs when the glacier shifts as this movement abrades the surface of the sea bed. The fragments from this movement are crushed and grounded together in a solid mass which then form the walls of a peak or mountain.

Water

Water is an immensely strong element which has the ability to move large amounts of soil particles and other substances across a large expanse of land.

Soil erosion caused by water is more likely to happen in areas where there is a downwards slope in the landscape.

There are four types of water based soil erosion which are:

  • Gully
  • Tunnel
  • Rill
  • Sheet

Gully erosion occurs where the flow of water has resulted in a channel along the direction of that flow. An example of this is the creation of gullies in ruts caused by vehicles.

Tunnel erosion tends to develop in soils which contain several layers: these layers are more effective at transporting water than the surface layer of soil.

Rill is a form of erosion in which several small channels are cut into the soil by water flow.

Sheet erosion is the least noticeable of the four. It still involves the removal of soil by water flow but does not lead to noticeable water channels.

Man-made erosion

This accelerated form of erosion is caused by human processes. For example, changes in the way land is used or new drainage processes can affect sedimentation load.

Another example is dredging or channelling to improve the angle of a slope or the speed of a stream. The problem with this is an increase in soil erosion and the capacity to transport a large volume of sediment.

The conversion of an area of wetlands into croplands is another cause of erosion which is more than likely if bare soil is exposed to the elements.

Impact of soil erosion and sedimentation

There is a correlation between these two effects and the environment. Soil erosion reduces the effectiveness of soil which means a drop in crop yields and potential hardship for farming communities, often caused by the increased costs associated with drainage systems.

Excessive sediment load has a direct impact upon marine life and can result in the destruction of natural habitat as well as certain species. In some cases this can affect the entire ecosystem.

Soil erosion and sedimentation control

This is an issue which is of particular concern in Hawaii. The waters which surround Hawaii and the other islands are seen as a valuable resource and a positive contributor to its economy.

But soil erosion and sedimentation caused by construction work and man-made effluents have resulted in pollution in these waters. An example of this is areas of heavy sediment around the coastlines and coral reefs.

One solution to this problem is for companies to implement a series of 'best practices' which will help reduce soil erosion and sedimentation in these areas.