Community spirit, professional expertise and practical demonstrations were a feature of this erosion and revegetation workshop. Guest speakers David Hilhorst and Andy Taylor from South East Local Land Services and Scott Soper led an inspiring and educational day.
Here are ideas and strategies from the workshop.
Pioneer plants such as wattle add nitrogen to the soil and improve soil fertility and structure. You can use branches from these plants (preferably with seed attached) and lay them over bare ground to create a nursery for seeds and/or or tube stock.
Locally grown small trees including wattles, kunzea and tea tree can be lopped and placed strategically on an eroded gully floor, the branches can be bundled and pegged creating a brush raft. The raft areas catch sediment that can be direct seeded using native grasses, sedges and rushes.
Look for wet patches above and below small erosion head cuts and use these sites for revegetation using locally sourced plants. Use bendy plants that slow the speed of the water including Juncus species, Carex appressa and Lomandra species. Trees that grow thick trunks should be avoided in confined gully beds and streams because tree trunks can deflect flood waters into banks and exacerbate the erosion problem.
Protect your soil from erosion is by maintaining 70- 80% ground cover in your paddocks and by limiting stock access to dams and dam spill ways. Erosion can be caused by overland flows from vegetation removal, dams, roads and gullies and by subsurface water movement. You can use simple clues to help you read your land, for example, are larger trees dying in patches? This could indicate that salinity is a problem. The eroded site at the property we visited was most likely being impacted by saline ground water which we learned also affects the water quality in the dam.
Mapping shallow ground water with an electrical conductivity survey gives an insight into the depth of the water resource and the salinity of an area. Windellama Landcare owns electrical conductivity (EC) mapping equipment and it can be hired for use by property owners and contractors. You should seek advice from South East Local Land Services to help you plan your erosion control work and EC mapping – Contact your Local Land Services office.
Eroded patches of sodic soils in gullies look like candle wax or stalactites. You can do a simple sodicity test using a small clod of soil and a clear dish. If area around the clod becomes cloudy, this indicates that the soil is sodic and might be highly erosive. Soil sampling of your farm could help you decide if you should be planting salt tolerant species at an eroded site.
Saline and Sodic Soils – the Difference video
Weirs, rock structures and rock/wire mesh weirs are all examples of “controlled activities” that may require a permit. Contact the Office of Water for advice about building structures including dams in drainage lines. As a general principle, water should always be returned to the same drainage line not diverted to another site. Before undertaking major works in water courses and gullies it is wise to check that your contractor has sought the correct approvals.
Contact a water regulatory officer as listed on the Office of Water website, call the licensing information on 1800 353 104 or email firstname.lastname@example.org for more information.
Jute mesh or hessian can be used on bare eroded sites to create zones where vegetation can be established. ‘Burritos’ can be made by wrapping jute or hessian fabric around a mixture of forest mulch and compost which can then be laid on the contour and held in place using wire pegs. Mulched areas can then be seeded with a soil conservation grass mix or local native grasses. Once micro climates have been established other plants can be encouraged to grow using the brush raft technique described above.
Weeds such as blackberry and serrated tussock can be used as a resource to help provide mulch, organic matter and plant cover at eroded sites if they are already growing there. It is important though to manage weeds to prevent flowering or setting seed by cutting, spraying or manual removal. Chip and spray the weeds or cut the canes and leave them in situ on the gully floor or bank, this slows the flow of water and traps sediment. The area can be then planted with desirable plants and grasses. The thorny plants can act as protection for new plants during establishment. Continual monitoring of weed prone sites is important.
The SIX Maps website can be used to work out the size of the catchment for an erosion head cut. For example, using SIX Maps, Andy Taylor estimated that for 1 in 50 year high rainfall events, the gully on this farm would have one tonne of water per second flowing over it. That is equivalent to one intermediate bulk container (IBC)/second. Estimating catchment size, soil testing and electrical conductivity testing are just some of the tools that can be used when planning erosion control measures.
Further information and resources
Gully Erosion Assessment and Control Guide
The Farm Dam Handbook
Rural Living Guide – A guide for Rural Landholders in the South East
Guide to Managing Ground Cover – MLA
DPI Erosion Website
Grassland Flora – a field guide for the Southern Tablelands
Native tree and shrub resources
SIX Maps – mapping tool
This event was made possible with funding and in-kind support from South East Local Land Services.