Help! I have soil erosion? What do I do? How do I stop it? How can I protect my soil and landscape? What is causing it? These are questions I get all the time from landowners, land managers, and custodians of country. The good news is that you can troubleshoot your erosion before needing to get an expert.
Erosion is the loss or transport of soil into air and water. Soil erosion occurs when the soil surface is exposed to elements, such as wind and water. Exposure of soil can occur through deforestation, agriculture, engineering activities, mining, or other management practices that expose soils that would otherwise be covered by vegetation or organic material. This exposure increases the energy of wind or water on soil surfaces, and results in the movement of soil away from the place it should belong.
There are different types of erosion. Some common examples include:
Sheet erosion ― loss of a uniform layer of soil across the entire surface of a soil
Rill erosion ― loss of soil in small channels (<30cm deep) across surface of the soil
Gully erosion ― loss of soil in deep and wide channels, usually along areas of water drainage
Tunnel erosion ― sub-surface erosion, where water moves through the soil and causes soil to be lost as a tunnel below the surface
Bank erosion ― loss of soil on the banks of waterways, including streams or rivers (see photo)
Wind erosion ― loss of soil into the air
Here in the Victorian Goldfields, just like around much of Australia, we have a range of soil erosion problems. This includes examples of all of the types of erosion listed above!
In an earlier blog, I talked about the loss of soil from mining and deforestation. Much of this would have been sheet, rill and gully erosion. The skeletal soils we see now, full of rocks, are a legacy of the soil that was washed away after it was exposed from gold mining. If you are walking out in the bush, you will often come across gully erosion – some has stabilised as our forests recover, whilst some gullies are still actively eroding during rainfall events. What can we do about the erosion that is still occurring? And what can you do about erosion you find on your property?
For all erosion the key is to a) identify the type of erosion, b) identify the source of erosion, and c) reduce the energy of wind or water on soil surfaces, and to protect soils by making them less exposed to the elements. There are some types of erosion where this is easy, and others where this can be hard! If you have identified you have sheet and/or rill erosion, then there are some easy things you can do:
Ask yourself — What is causing the erosion? The key to fixing erosion is fixing the cause. This may be clear (i.e. erosion is from goldmining or lack of vegetation) or harder to understand (i.e. the start of the gully erosion is on my neighbours property). Is it from wind or water?
Plants — Get plants and vegetation into your soil to protect it from water and wind, and to help hold the soil in place.
Mulch and organic material — spread out weed-free mulch to protect the surface of your soil, or use other organic matter to slow down water, such as fallen branches across slopes. If you are undertaking agriculture, maintaining cover crops, stubble and organic matter can reduce wind, rill and sheet erosion.
Fence out animals ― keep out any animals that may use this site, as best as you can, whilst you are undertaking stabilisation activities.
Slow down the water using the landform — if erosion is occurring down a slope, then you can put in breaks in that slope to help slow the water whilst also capturing the water for plant use. This may be in the form of laying branches or hay bales across a slope, or even building small soil banks (see photo below).
Reconsider land management activities ― ask yourself, is something I am doing causing the soil to be exposed? How can I change what I do to protect the soil?
I actually have sheet erosion at my place (see photos below). This erosion is caused by three things: poor storm water management, poor vegetation cover, and water repellent soils. To manage the erosion, I built some small soil banks across the slope. I protected these with logs, mostly so they didn’t get destroyed by my active dog! The banks have mulch in between, and I plan to revegetate between the banks with native plants. We are also taking actions to improve the storm water management, including better capture and reuse of water.
Maggie the dog inspects the soil and timber banks that follow the contour of the slope. These were installed to help slow the energy of water causing sheet erosion down the slope (Photos: J.Drake).
If you have identified that you have gully, tunnel or bank erosion ― make sure you really understand what you are doing before trying to remediate the erosion itself! Like rill and sheet erosion, you can implement the same management practices to reduce the energy of water or wind and protect the soil. These management practices alone, however, are often not sufficient to reduce or stop the erosion. This is because the cause of gully, tunnel or bank erosion is usually harder to identify, and there will be multiple-interconnected causes. For example, gully erosion may be the result of drainage off a road, along with the loss of vegetation and animal activity. Or tunnel erosion could be because water is being concentrated onto soil that has chemical and physical properties that make it more susceptible to erode. This means you will need multiple strategies to combat the erosion, and this may be when seek some professional advice.
Erosion control activities that focus on physical interventions within the gully, tunnel or bank erosion can exacerbate the erosion if it isn’t done properly. I have seen lots of cases where gully erosion control has focused on symptoms rather than the problem, and the techniques used (i.e. engineering structures, diversion etc) resulted in increased widening of the gully or the shifting of the erosion problem to another area. Care should be taken in understanding the complexity of the erosion issue and in implementing targeted options for managing the cause of the erosion.
Soil erosion is complicated!! There are a lot of interplaying and interconnected factors that cause soil erosion. This includes land management, vegetation, chemical, physical and biological properties of soil, types of disturbance, engineering etc. If you are unsure about what may be causing your erosion, if you have severe erosion problems, or you are unsure how to fix it, we suggest seeking a qualified person to help identify the cause of erosion and help you develop a management plan.
There is lots of information about erosion, including how to evaluate and manage. Some of my favourite resources include: