How Does Vegetation Prevent Erosion?
When told that water conservation is crucial, we save. Reduce, reuse and recycle have become common in households to battle pollution, but when it comes to erosion control, most of us are baffled as to how to combat it. The deterioration of soil by water, wind and other natural forces can be a major ecological problem if not handled correctly. Here at Spray Grass Australia, we believe that vegetation is the best form of erosion control.
What is Soil Erosion?
Soil erosion refers to the wearing away of nutrient-rich topsoil in fields and slopes by natural forces such as water and wind. Erosion occurs in three distinct actions – soil detachment, movement and deposition. The topsoil, which is high in organic matter and fertility, is displaced and relocated either on site or is carried off site, filling drains or contaminating waterways. Soil erosion is capable of crippling the productivity of farmlands and destabilizing slopes causing potential harm for human life, property and animals.
Runoff water after a heavy rain fall is partially to blame for soil erosion. Runoff refers to water that flows over the soils surface resulting from over saturation and can no longer absorb more water. There are four main types of water erosion; sheet erosion, rill erosion, gully erosion and bank erosion. The higher the intensity and duration of the rain fall, the higher the erosion potential is. Raindrops can break down the soil aggregates and disperse of it. In areas where there are lighter aggregate materials, such as sand or clay, it is easier to remove soil by either raindrop splash or runoff.
In terms of slopes, the steeper and longer it is, the greater potential of erosion. This is due to the increased velocity of water, which permits a greater degree of scouring.
Wind erosion generates mostly in flat, bare areas or areas that soil is loose, dry and/or granulated. The process of wind erosion works to detach soil particles from the surface and carries them away to displace them elsewhere. This results in soil loss, dryness, deterioration of soil structure, nutrient and productivity losses and can cause air pollution. Soil particles move in three different ways depending on their size and wind strength – suspension, saltation and surface creep.
How Vegetation Helps
The probability of soil erosion increases if the soil has little or no vegetative cover (plants, grasses, crop residue or trees). Plants and residue cover aid by protecting the soil from the effects of raindrops and splash, slowing down the movement of runoff and allowing any excess surface water to infiltrate the soil. Plants have extensive root systems assist to “grab onto” soil and keep it bound together, reducing displacement. These roots also help to stabilise embankments and slopes, limiting the risk of landslides. You can see this when you pulled plants such as weeds, vegetables or even grass out of the ground as the soil clumps to the roots. Vegetation that completely covers the soil and intercepts all falling raindrops on or close to the surface are the most effective in controlling soil erosion.
Mulch adds further assists in protection from erosion, especially in newly seeded areas. Mulch protects the ground from rain and wind while seeds germinate. It reduces the loss of soil moisture during extended dry periods leaving the soil susceptible to wind erosion. In areas exposed to severe conditions, mulching is necessary to establish vegetation and stop erosion. In these, hydromulching is the preferred method.
A lack of wind breakers, such as trees, shrubs, crop residue, allows the wind to further displace soil particles for longer distances, increasing abrasion and erosion. It is important to make note that the type of grass or plant species will alter effectiveness.