Before you start
Avoiding erosion issues on your property can often be as simple as maintaining groundcover and keeping livestock out of sensitive areas such as drainage lines and waterways.
Get advice on:
Assessing the scope of work
Sometimes the only way to effectively manage erosion is through installing erosion control structures.
Before beginning any erosion control works:
- Assess the type and scale of erosion.
- Identify the size of the contributing catchment.
- Understand your soil type and slope.
- Ensure any required approvals are obtained.
Prioritising erosion control activities
This video explains how to assess erosion on your property and prioritise control and repair.
Identifying priorities for erosion control on your property
Minor erosion can often be managed by installing biodegradable natural structures. These structures temporarily slow water flow, trap sediment and allow vegetation to grow
Minor erosion is usually:
- in small catchments (under 50 hectares)
- not on steep land
- has erosion points of 50cm or less.
In small catchments, you can use a variety of earthmoving techniques to stabilise gullies. This will depend on the site characteristics and available funds.
The larger the catchment size, the less options are available. Professional guidance is recommended.
For advice on design, construction and maintenance of erosion control works, you can contact Local Land Services.
Minor erosion control methods
Small scale erosion control on my property
Jute mesh
Jute mesh is a 100% biodegradable matting used to stabilise banks, slopes and large areas of bare soil. It minimises sediment loss while enabling vegetation to grow through it. Installing jute mesh is simple, requiring a mallet, pins, seed and/or tubestock.
Jute mesh installed with hay bales to divert water away from an active erosion point.
Hay bales
Hay or straw bales are a simple and affordable way to temporarily reduce sediment from entering waterways. They are typically installed using timber stakes to trap and filter sediment. Note that they may pose weed risks, so monitor these sites overtime.
Coir logs
Coir logs are made from coconut fibre and are flexible yet durable. They can be bent to fit the landscape and maintain their structure for a long time. Coir logs are simple to install using star pickets or wooden stakes. Vegetation can also be readily established by planting directly into and/or behind, the coir log.
Coir logs installed to slow water and trap sediment.
Earthwork options for larger areas
On larger catchments, erosion control works will need detailed design to ensure they can handle storm events. In most situations, structures will need to cater for at least a 1 in 50-year storm event.
For this kind of work, you should seek professional engineering advice.
You are responsible for ensuring all appropriate approvals are in place before any earthworks begin.
Large scale earthwork options to control erosion include:
- gully control structure (dam)
- diversion banks
- incline pipes (pipes in banks)
- gulling filling and shaping
- flumes (concrete or rocks)
- grade stabilisation structure (rock ramp)
- v-notch weirs
- strategic fencing.
Gully control structure dam
A gully control structure built above the gully head will stop run-off water from flowing over the gully head by storing the run-off in a dam. This structure also provides a sediment trap.
The structure could be built within the gully “drowning out” the active gully head with the stored water. A trickle pipe installed through the gully control structure can release water slowly over time, protecting the main spillway from erosion.
These structures allow a large volume of water to be stored between the pipe level and the spillway level, which can be safely released through a trickle pipe.
Such systems are ideal for continuous gully systems where runoff water cannot be handled with a bank and pipe system. This type of structure should be designed to cater for the relevant run-off volumes of the catchment.
Diversion banks
Diversion banks divert water away from actively eroding areas either to a safe disposal area or to another structure such as a dam or flume.
For gullies on small catchments, or discontinuous gullies, a diversion bank/s may be all that is required for stability. On larger gully systems, diversion banks may be needed to divert water to another structure such as a flume or gully control structure.
Banks should be designed to cater for storm events, to ensure the banks are not over topped or eroded during a storm event.
This diversion bank transports water away from the gully head and into a dam.
Two diversion banks at the midpoint of the photo safely transport runoff away from the main gully and lateral gully (at bottom of image) both with active walls.
Pipes in banks
Trickle pipes are recommended in some situations including:
- On catchments up to five hectares where there is no stable area to divert runoff and no other structure is required. The pipe caters for most small - medium trickle flows.
- Where there is a constant trickle flow that needs to be managed to keep other areas dry.
Gully filling and shaping
Before filling can occur, diversion works must be properly designed and constructed to minimum recommended standards. Filling of a gully should only be undertaken in those areas where all surface run off has been diverted away and there is little or no groundwater on the site.
Once water is diverted away from an eroding area it can be seeded, mulched and stock excluded to stabilise the area. For pastoral lands and where the soils are highly dispersible, shaping gullies is not usually recommended.
Filling a gully, (for example with clean fill) should only be undertaken after gaining the necessary approvals from Local Council.
Flumes
Flumes are used where it is necessary to convey water to a lower level over a short distance. They are designed in such a way to dissipate the erosive energy generated by dropping the water in this fashion, for example into the stable floor of steep-sided gullies.
All flumes are engineering structures and should be designed by engineers to cater for at least a 1 in 50 year storm event.
Concrete flumes form a stable, long life structure for conveying large volumes of run-off for long durations to the floor of highly active gullies. They need to be properly designed and constructed. Subsurface drainage may be required.
Grade stabilisation structure - rock ramp
These structures are also used to provide a stable disposal site for run-off water within a gully. Once the storm flow has been calculated then the rock size can be determined. A mixture of sizes is best to key-in the larger rocks and ensure there are no voids creating a weakness in the structure.
A cut off trench should be installed to stop any undermining of the structure. The cut off trench is lined with geofabric which extends for the length of the structure. Rocks are then placed on geofabric. Rock is an option for providing gully floor stabilisation.
V-notch weirs
V notch weirs are used to stabilise gully floor headcuts. They are only used to stabilise a drop of 300-400mm. They are constructed from hardwood logs. Two logs are buried into the ground forming the cut off trench. The third log sits above to stabilise the headcut, slow and direct the flow. The V needs to be pointed upstream to ensure the water is directed towards the centre of the gully. Rocks are placed behind the v-notch weir to provide scour protection.
When to seek professional advice
Seek professional or engineering advice when:
- the catchment is larger than 50 hectares.
- major structures such as dams, flumes or diversion banks are required.
- the work involves waterways or areas needing regulatory approval.
Contact Local Land Services for support with planning, approvals and technical guidance.
Contact Local Land Services NSW
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