Soil Science

Erosion & Deposition

Water erosion

Erosion is often considered only as a form of soil degradation resulting from poor land management. However, geological (as opposed to accelerated) erosion, together with sediment deposition, are important natural landscape-forming processes.

Erosion by water often removes soil material from steep upper slopes and deposits sediments on lower slopes where the gradient is less. As sediment moves downslope, it is sorted, and coarser, sandier material is deposited first. Finer clays may be deposited further downslope or move as suspended load past the slope and into streams.

In forested catchments, erosion rates are typically less than 1 tonne per hectare per year.


Landscape formation

Landscape formation

In Australia, the role of water erosion and deposition in landscape formation is nowhere more significant than in the Murray-Darling Basin.

Alluvium derived from the eastern highlands, as well as windblown material, has been deposited in the inland plains and forms the basis of soils that support a major part of Australia's agricultural output. Deposition has occurred over a long period, with sediments near the surface being of Pleistocene or Tertiary age in many places.


Wind erosion

Erosion by wind has also played a significant role in shaping the Australian landscape.

For example, the dune fields of central Australia are composed of sand remaining after clay has been winnowed from the soil and blown out to sea. In southeastern Australia, many soils contain a component of aeolian or wind-blown material.

For more details on wind and water erosion, refer to the Erosion and USLE module in the 'Hydrological Cycle' section.

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