Erosion control and remediation
On many waters we visit, erosion of banks and islands is a significant problem and in turn leads to many other problems that can have direct effects on water quality and the dependent ecosystem. Erosion is commonly caused simply by the actions of water moving naturally, whether flowing in a stream or river or by wind and wave action on exposed banks of ponds, lakes and reservoirs. There are, however, many other causes including erosion from inlets, livestock drinking, waterfowl moving in and out of the water, crayfish burrowing and in one unusual case for us the use of bumper boats on a lake!
Bankside erosion often releases nutrients into the water which are utilised by algae, contributing to algal blooms. In many cases, especially where the banks are clay, erosion contributes to turbidity (cloudy water). There are many other aspects of water quality that can be affected by erosion and our consultants are well placed to identify the problems and advise the client of the best and most sustainable solutions.
Initially, in cases where erosion is a problem, we recommend that the cause is investigated and remedied before work is completed to control future erosion. This can be as simple as changing the way water flows in a stream, to trapping non-native crayfish where burrowing is a problem. Where livestock and waterfowl are the root cause of erosion, we can design and install dedicated, engineered areas where they can enter and exit the water body without ruining the banks.
There are several ways to remedy erosion problems although in the vast majority of cases the installation of a specialised geo-textile, called Nicospan, supported by timber posts, is used to rebuild banks. This technique is well recognised within the industry as being the most environmentally sound method available and soft engineering such as this has largely replaced the methods of old, such as sheet piling and concrete revetments.
Geo-textile engineering with Nicospan can easily be incorporated into most environments and when completed is barely noticeable. This technique can be used to create load-bearing banks and even islands in an already established water. On completion the geo-textile banks are planted with a mix of UK-native plants to provide structure and stability to the remodelled banks. A further advantage to the use of geo-textile bank stabilisation is the flexibility: banks can be modelled to virtually any shape and height, either to match with the existing banks or in some cases to create a very different bank line.
A further method where conditions allow, is the use of coir logs or mats. Coir provides an excellent medium in which to grow plants. The roots of these plants then grow through the coir to provide stability and structure to the weak banks. After a number of years the coir logs/mats decompose completely and the plants take over the job of protecting the banks.
In many cases bank stabilisation work is completed using a combination of geo-textiles and coir products. This gives the best aesthetic finish as well as massive structural integrity once the aquatic plants have established fully.
We can of course employ other methods and are currently involved in projects as diverse as rebuilding an island, without de-watering, using rock-rolls (a type of flexible gabion), to the use of deciduous timber boarding for a small spate stream. We can find solutions for almost any water and have a firm understanding of the Environment Agency mandatory requirements for works to river and stream banks, this ensures you get a high quality service tailored to your individual water.
To show our capabilities here are some previous projects completed by our consultants:
- Major restoration and creation of banks on a National Trust lake in West Sussex
- Rebuilt banks following extensive de-silting on a Cotswold farm pond
- Rebuilt banks where water erosion had occurred on a private estate in the Black Mountains
- Rebuilt the banks of a Cambridgeshire village pond