Soil erosion
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.
Further information—fact sheets
- Erosion control in cropping lands—L13 (PDF, 102K)*
- Erosion control in grazing lands—L91 (PDF, 127K)*
- Gully erosion—L81 (PDF, 234K)*
- How healthy is your watercourse?—R34 (PDF, 193K)*
- Managing stock in and around waterways—R33 (PDF, 222K)*
- Stream bank planting guidelines and hints—R31 (PDF, 229K)*
- Stream bank vegetation is valuable—R30 (PDF, 132K)*
- What cause bank erosion?—R2 (PDF, 160K)*
- What causes stream bed erosion?—R20 (PDF, 645K)*
Further information—Reports
- Managing grazing lands in Queensland (PDF, 642K)*
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 limited—only small areas are cultivated for horticulture or vegetable growing where irrigation is available.
Further information—fact sheet
Wind erosion—L259 (PDF, 117K)*
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 and water storages
- overall reduction in water quality of creeks, rivers and coastal areas.
Eroded soil (which can contain nutrients, fertilisers or pesticides) may not have a fast track to streams—it can be deposited where there is a reduction in the slope of the land, in sediment traps, along contour banks, or in grassed waterways, dams, or wetlands.
Heavier soil particles will be the first to be deposited, while finer colloidal clay particles may remain in suspension. Soil removed by gully erosion, especially finer colloidal clay, may be transported directly to a creek or river.
Further information—fact sheet
- Catchments and water quality—C2 (PDF, 1.4M)*
Erosion control
The principles of controlling erosion are to:
- use land in accordance with its capability
- protect the soil surface with some form of cover
- control runoff before it develops into an erosive force.
Land capability
Soil type and land slope determine how vulnerable land will be to erosion. If the risk is serious, the land may be unsuitable for any agricultural use, or suitable only for a type less conducive to soil erosion.
Surface cover
Adequate surface cover is a major factor in controlling erosion because it reduces the erosive effect of raindrops falling on bare soils and the ability of winds to remove soil particles.
Using implements that can handle stubble, rather than burning it, and using herbicides to control weeds, makes it possible to employ minimum till and zero till practices, which minimise erosion in cropping areas. In the cane industry the use of green cane harvesting techniques allows farmers to maintain a trash blanket on the soil surface to protect against erosion.
In grazing lands stock numbers need to be managed to match the current and expected seasonal conditions. Graziers need to make regular decisions about how many animals they should run on a piece of land taking into account the added impact of native herbivores and feral animals.
Runoff
Though surface cover encourages runoff to spread rather than to concentrate, it still tends to concentrate as it moves downslope. In cropping lands, this effect is mitigated by using structural measures such as contour banks and grassed waterways in upland areas, or strip cropping on floodplains.
On roads, tracks and fencelines erosion can be managed by carefully siting these structures and by applying runoff control measures such as whoa boys and spur drains
Further information and fact sheets
- Managing grazing lands in Queensland (PDF, 642K)*
- Managing for drought in grazing lands—L90 (PDF, 76K)*
- Soil conservation planning in cropping lands—L83 (PDF, 112K)*
- Runoff control measures for erosion control in cropping land—L35 (PDF, 200K)*
- Controlled traffic farming - soil conservation considerations—L146 (PDF, 322K)*
- Maintaining contour banks—L202 (PDF, 101K)*
- Contour bank specifications—L205 (PDF, 82K)*
- Erosion control on property roads and tracks - cross sections and locations—L239 (PDF, 218K)*
- Erosion control on property roads and tracks - managing runoff—L240 (PDF, 227K)*
- Erosion control on fences and firebreaks—L241 (PDF, 178K)*
- Soil conservation waterways - Planning and design—L272 (PDF, 145K)*
- Soil conservation waterways - Construction and management—L270 (PDF, 94K)*
- Soil conservation waterways - Plants for stabilisation—L271 (PDF, 120K)*
Design manual
The Department of Environment and Resource Management is producing a web based publication titled Soil conservation measures—Design manual for Queensland. It aims to capture the available knowledge on this topic for use by private consultants and staff employed by regional bodies. There are four sections to the manual:
- Planning
- Runoff estimation
- Channel design
- Special applications
- Ch 1. Introduction (PDF, 36K)*
Section A: Planning
- Chapter 2. Soil conservation planning (in progress)
Provides practical information on the planning of soil conservation measures and is of most relevance to broadacre cropping. Information relating to the Soil Conservation Act 1986 is included. Some chapters in other sections (e.g. the chapter on horticultural applications) will also contain information related to planning..
Section B: Runoff estimation
This section contains information on the first step in designing a soil conservation structure—estimating the rate of flow that the structure will need to accommodate. It describes the processes related to runoff (with a special emphasis on the impacts of stubble retention practices), and two methods of estimating runoff for small rural catchments.
- Ch 3. Runoff processes (PDF, 124K)*
- Ch 4. Designing for risk (PDF, 26K)*
- Ch 5. Peak discharge estimation (PDF, 20K)*
- Ch 6. Empirical version of the rational method (PDF, 134K)*
- Ch 7. The Darling Downs regional flood frequency version of the rational method (PDF, 146K)*
Section C: Channel design
The second step in designing soil conservation measures is to design a structure that can accommodate the estimated runoff. Some general principles are included in Chapter 8 with more specific guidelines provided in the other chapters.
- Ch 8. Channel design principles (PDF, 257K)*
- Ch 9. Contour banks (PDF, 306K)*
- Ch 10. Diversion banks (PDF, 78K)*
- Ch 11. Waterways (PDF, 350K)*
Section D: Special applications
This section includes information on a number of specialist topics
- Ch 12. Floodplain applications (PDF, 106K)*
- Chapter 13. Controlled traffic (in progress)
- Chapter 14. Vegetated strips in upland areas (in progress)
- Chapter 15. Horticultural applications (in progress)
- Bibliography (PDF, 49K)*
Contact
For enquiries, or if you have any problems downloading these PDFs, contact DERM for further information:
Client Outcomes
Product Delivery
Department of Environment and Resource Management
GPO Box 2454
Brisbane Qld. 4001
Email Product Delivery
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Last updated 10 October 2011
