The soil crust is made up of lichens, leaf litter and soil invertebrates that together protect the soil surface and increase its ability to absorb water. Erosion occurs when the soil crust and its cover of vegetation is damaged.
The poor placement or design of tracks, dams and infrastructure, over-grazing and the compaction of the soil, often caused by the action of hard-hooved animals, and vehicles are major causes of erosion. With no vegetation cover to slow down its movement, water that would normally soak into the soil can run-off, washing more soil away and creating new drainage lines.
We use a number of techniques to control erosion. They range from simple silt traps to major earthworks.
Simple silt traps can be created by filling erosion gullies with tree branches to slow the flow of water over the ground and catch waterborne soil particles and seeds. Leaves eventually drop off the branches also helping to trap seeds, soil and organic matter and over time the area begins to stabilise as the soil is held together and new plants establish.
Similarly simply cutting some bands into areas of compacted soil can help reduce water run off and allow sediment and water to pool, encouraging new plants to establish.
Major earthworks are sometimes needed to remove levy banks or dams that disrupt the natural flow of water, or to repair serious erosion gullies. The Gungoandra Creek rock weir and fish way on Scottsdale Reserve is a great example.
How the land responds
The seeds of plants caught in silt traps quickly germinate and help to further slow the movement of water and stabilise the soil.
Restoring the natural flow of water across the land surface helps to return water to creeks, rivers and natural aquifers and nourishes the soil and the native habitats.