There are a range of measures land managers can undertake to repair erosion damage, that will also ensure riverbanks, floodplains and gullies are better protected against future flooding events.
Key points to consider:
– Erosion is accelerated when little or no vegetation exists on or near the stream bank to bind soil together. Pasture grass alone does very little to protect riverbank soil from flood events.
– The bigger the waterway, the wider the riparian zone needs to be to withstand the impacts of flood events. For major rivers, the riparian zone should be greater than 50 metres wide on both sides of the bank. For minor creeks and gullies, riparian zones should be at least 10 to 20 metres wide on both sides of the banks.
– Riverbanks/riparian zones require a mixture of reeds, grasses, shrubs and trees that have different root types (for example, fibrous, tap, creeping or tuberous) to help bind and hold the soil in place, and keep it from washing away during floods.
– Livestock can cause erosion by compacting soil, creating ruts, trampling vegetation, spreading weeds and browsing native vegetation.
Landholders can reduce erosion on their properties by:
– Restricting and managing the length of time livestock graze in the riparian zone/riverbank edge.
– Installing off-stream water.
– Establishing or maintaining a wide, vegetated riparian zone.
– Controlling weeds.
– Talking to their neighbours about how to better manage their shared waterway.
Riverbanks can quickly lose their integrity once soil is eroded and washed away.
Once soil is removed and the banks begin to steepen, soil not held in place by a variety of roots will erode quickly during a flood event.
Recovery options will vary depending on the size of the riverbanks and gullies, the amount of damage, and previous management of the riverbank and riparian zone.
Effective erosion recovery and ongoing management ensures beds and banks are better protected against future floods, which should result in less damage.
Options to reduce the risk of future erosion include:
Fencing to better manage stock access: In flood-prone areas, fencing can be difficult to manage. However, there are inexpensive electric fence options that can protect considerably large areas and be retrieved quickly prior to or after flood events.
Widening your riverbank vegetation: Native vegetation (trees, shrubs and grasses) are the best bank protectors we have.
Trees like water gums and shrubs like lomandra and river bottlebrush can play a major role in slowing flows and binding soils together on a riverbank. Purchased as tubestock, these plants are often less than a few dollars each and easy to plant.
Revegetation should be undertaken using ‘local stock’ and aim to mimic what would naturally grow in your area. You should aim to have a mixture of native trees and shrubs that have a variety of root depths to hold soil in place.
Controlling weeds in riparian zones: Weeds can outcompete native vegetation and dominate the riparian zone. With their shallow roots, they leave riverbanks more susceptible to erosion. Vine weeds should be aggressively managed as they are known to pull trees over during flood events creating large voids in the riverbank.
Let sleeping logs lie: Any native tree that has fallen into a waterway is a ‘snag’ protected under the Fisheries Management Act 1994. Snags play an important role in the river system by creating fish habitat and slowing flows to reduce erosion. With permission from DPI Fisheries, snags can be repositioned to ensure they benefit bank stability.
For more information contact your local council, the Department of Primary Industries or your Local Land Services.
Source: https://www.lls.nsw.gov.au/
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