What is the main issue with Continuous Erosion? The clue is in the name – it is continuous. On bare soil just one drop of rain will dislodge soil particles. If you consider this in terms of a normal rain shower then there can be significant movement in these natural slopes.
If you consider this in terms of a rainstorm a significant change can occur in slopes – and the worst case scenario of this is a significant land slide. But it’s not just rain – wind and foot traffic can also attribute to erosion of slopes.
So, it is important to protect all natural, mud based slopes from erosion to protect from this significant movement of soil.
Natural solutions
The natural solution to the prevention of slope erosion is plants and vegetation. By creating a natural covering for the soil, less water and wind can move the soil on the slope, and the slope will be less affected by footfall. The roots of a plant play a part too, helping to bind the soil underground making erosion a more lengthy process.
The type of plant that is used makes a big difference to it’s effectiveness preventing soil erosion. Choosing a ground cover plant will allow for the greatest coverage of the slope to prevent surface erosion, where a creeping shrub will prevent surface and subsurface erosion with it’s extensive network of roots under the surface of the slope.
Although plant coverage on slopes is often highly effective, and preferable as a natural and sustainable solution, it is not always enough to ensure that erosion of slopes is prevented. Plants are susceptible to disease and will die and mature in changing seasons, leaving parts of the slope vulnerable to damage.
Engineering Solutions
Developed in the early 1970s, the process of using soil nails in natural slopes has been been widely accepted as a method of providing support to a natural slope. Typically a structural concrete facing will be applied to the slope in order to connect the nails to the earth, then the nails are inserted into the earth using a drill or auger.
Applying an impermeable concrete facing to the slope completely covers the slope, preventing all types of erosion, but it is especially effective in areas where erosion due to water is a significant issue.
Eco-Engineering
Combining engineering solutions and vegetation as a way of controlling slope erosion is commonly termed ‘eco engineering’. Eco-engineering is often the preferable method of stabilising slopes, as it is both environmentally friendly and a reliable method to prevent land slipping. Many eco-engineering solutions involve the introduction of compost to a slope. For example:
A Compost Blanket can be used to cover a surface which has show to hold to many slopes without slipping and provides a protective layer to the natural slope beneath. These often help to retain moisture on the slope which will encourage the growth of vegetation forming a natural protection for erosion.
A Compost Sock is a tubular geotextile mesh filled with compost and are particularly used for the prevention of erosion from flood waters, and will also encourage growth of vegetation.
A Compost Geosystem is designed to protect from a variety of natural erosions, including slope reinforcement, drainage and erosion control, and they are formed of a variety of geotechnical cellular confinement systems.
Although compost is often the preferable method of preventing erosion on slopes, it has it’s limitations. Depending on how steep the slope is will significantly affect which solution you need for your slope. Compost blankets can be used on some 2:1 slopes – however in some cases a compost sock may be more suitable here to prevent slipping of the compost itself.
AUTHOR BIO
This article is by Maccaferri UK. Renowned as the world leader in gabion retaining structures for over 130 years, Maccaferri provides innovative solutions and products to the construction industry.