Managing soil erosion and water run-off on a construction site is vital work which can be achieved by mixing both nature and nurture.
Installing geotechnical products in the ground on developments will allow vegetation to establish, as the former actively encourages the latter to grow to create long-lasting erosion control.
Soil erosion is cause for concern on construction sites as the ensuing silt contamination it creates is one of the largest causes of pollution in water courses. Erosion occurs as rainfall displaces soil, carrying soil particles, sediment and silt away, and can also be exacerbated by vehicle movements and works on-site.
Without methods for erosion control, bare earth left exposed to the elements will move, risking polluting water courses and surrounding areas such as access routes. As well as causing pollution, which could incur fines from the EA or SEPA, this erosion has the potential to delay a project.
Where soil erosion by water run-off is taking place, vegetation will slow down the velocity of water and provide stability to the surface, particularly on slopes – with roots slowing and absorbing the flow of water. Planting and encouraging vegetation growth is vital, but as this takes time to establish, installing geotechnical products will slow down water and nurture the growth of grass or plants.
Which products are right for a project will depend on a number of factors, including soil type, ground and weather conditions, the size of disturbed areas, vehicles movements across site and the levels of filtration or drainage required.
On slopes or embankments, installing biodegradable mats, made from coir or jute, will immediately minimize soil erosion while also encouraging vegetation to establish.
Biodegradable mats provide reinforcement by anchoring topsoils and sediments, as well as seeds, before strengthening and supporting roots as vegetation establishes and plants grow. Both types of matting can have seeds sewn in so planting is part of the installation process. With a variety of weights and weaves available, degradation of the product then takes place at whatever pace suits the project – short, medium or long-term.
Coir matting provides medium- to long-term reinforcement on all gradients of slope and is best suited to wet areas or river embankments where more water erosion is expected. The fibre is highly absorbent, catching water and silt, allowing it to slow water run-off while its open weave allows grass, shrubs and plants to establish and grow through as it gradually breaks down.
Jute matting provides short- to medium-term reinforcement on all gradients of slopes and is best suited to relatively dry areas where grass or turf will grow. It is lightweight so easy to install and an economical product for use on large areas, providing immediate soil reinforcement.
Figure 1 – Erosion blanket on embankment
For steep slopes or areas with poor soil, permanent erosion control matting, made from non-degradable synthetic materials, can offer long-lasting protection to stabilise the ground while also promoting vegetation growth by binding with roots.
At the base of slopes, installing a silt fence will capture any silt or sediment which finds its way through the matting, containing the silt and preventing it from contaminating nearby water courses. These geoproducts, also woven but made from synthetic materials, will provide short- to medium-term protection on a site.
Figure 2 – Silt fencing
For long-term protection, promoting the growth of vegetation is key to managing the velocity of water run-off and controlling erosion. Installing products which support prevention will always be more effective and more economical than cure – particularly as the EA, NRW, NIEA and SEPA all have powers to impose heavy fines if pollution impacts water courses surrounding a construction.
Making informed choices about which geotechnical products are installed – whether biodegradable or permanent, and at the base or within slopes – will ensure effective measures that last long after a development is completed. Working with experts, with knowledge and understanding of erosion control to design optimum solutions, will support this.
