Hamlet A Euolgy

Types of erosion

Soil erosion caused by water and wind is a widespread problem in both rural and urban areas of Queensland.

Water

The state’s high intensity summer rainfalls mean there is a significant risk of erosion by water.

Hillslopes are susceptible to both sheet erosion, and rill erosion (where small channels up to 30 cm deep form) depending on:

the intensity of rainfall (erosivity)

the nature of the soil (erodibility)

the length and steepness of slope

how the land is used and managed.

Gully erosion is highly visible and affects soil productivity, restricts land use, and can threaten roads, fences and buildings.

Tunnel erosion is the removal of subsurface soil. Initially, the surface soil remains relatively intact, but it may collapse as a precursor to the formation of a gully. Soils vulnerable to tunnel erosion have dispersible subsoils with naturally high levels of sodium. When clods of such soils are exposed to water, they readily break down into individual particles of sand, silt and clay which are easily removed by the movement of water through the subsoil.

Streambank erosion during flooding is a widespread problem. Streams at highest risk are those from which riparian vegetation has been removed.

Floodplains may also be susceptible to erosive flooding.

Wind

Wind erosion is a significant problem in the arid grazing lands of inland Queensland. It is most likely to occur when strong winds blow over light-textured soils that have been heavily grazed during periods of drought.

It contributes to scalding, a process that results in the formation of smooth, bare areas on impermeable subsoils.

These areas, which vary from a few square metres to hundreds of hectares, are difficult to revegetate due to the lack of topsoil, low permeability, and their often saline surface.

Wind erosion is generally not a serious issue in cropping areas, as most soils cultivated in Queensland have a heavy texture and form relatively large aggregates that are too coarse to become airborne in strong winds.

However, sandy soils are susceptible to wind erosion. Because they cannot store very much moisture and have low fertility, their use in Queensland is limitedвЂ"only small areas are cultivated for horticulture or vegetable growing where irrigation is available.

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Effects of erosion

Soil erosion removes valuable top soil which is the most productive part of the soil profile. This results in lower yields and higher costs of production.

The subsoils left after topsoil has been removed are often unable to support agriculture because advanced erosion causes rills and gullies that make cultivation paddocks unworkable.

Downstream effects include:

damage to roads and railway lines

siltation of watercourses