We were asked if we could help Irvine Angling Club by showing them how to stabilise erosion using green engineering techniques, or did we offer? I can’t quite remember how this came about but as ever, the Trust is willing to help any clubs that are willing to take our advice or ask for our assistance.
We visited the area a month or so ago to see what may work. There’s no shortage of willow around this area of the Irvine that could be used to install stabilisation techniques and cut erosion however, we thought we should provide a trailer load of fresh cut willow and brash faggots and we seized the opportunity of harvesting willow from the Galston site where contractors have been felling trees ahead of the main contract to realign the river. The realignment is going to utilise a combination of hard and soft engineering techniques but when it will be delivered is as yet unknown.
We arrived at the lower Irvine this morning with materials and equipment and met a handful of club members keen to hear what we had to suggest and to help with the work. First off we showed them how to make faggots and bundles of materials for use on the banks. Once the trailer was empty, we moved onto the installation.
Typically when green engineering is mentioned for river restoration , people automatically think of willow spiling and there’s certainly a place for that but here in Scotland, unless you have an unlimited supply of the perfect raw materials, it can be expensive to purchase ready cut whips from south of the border. We typically employ a variety of methods using willow rather than focussing on spiling (weaving) alone. Much depends on the banks and habitat you are working in and we’ve developed other techniques that we find every bit as useful for trapping sediment and (re) building banks. Major benefits over spiling are the speed of installation and the ease with which this technique can be installed.
Willow rods, branches, whips, cuttings, call them what you like, are laid on a saw horse then compressed firmly into bundles and secured with bailing twine or sisal. We tend to make these in 7- 8′ lengths. The same process is used to make brash faggots although they are much broader and more firmly bound but effectively the process is the same. As we use varying species and thickness in our bundles, you end up with diversity in the results and that’s got to be better than creating vast monocultures of willow.
These bundles are fixed to the toe of the bank or riverbed and staked in place using willow stakes. Effectively you create a mass of cuttings that will root into the substrates and send shoots along their 8′ length into the air. The results is a stand of willow plants rooted into the bed or bank. Within a season or two, the shoots form a dense cluster that slows the flow of the river causing sediment to drop out of suspension. The result is the bank height increases as more sediment builds. The roots bind the banks together preventing further erosion. An additional benefit is that you create a wildlife habitat that offers birds and invertebrates shelter and the plants provide shade over the river and cover for fish.
We installed several metres of willow bundles this morning supplemented by brash faggots to add robustness and trap further sediment. The area we worked was the inside of a bend where it has started eroding during spates. This is probably due to the rock armour that’s installed on the outside of the bend. Anyway the rock armour won’t be going anywhere so rather than allow the erosion to continue unchecked, we attempted to improve bank stability on the inner bend and hopefully this will prevent further bank loss.
Now that members of the club have seen what is required, they will be able to continue with these techniques themselves. Hopefully club anglers will help them as the more that get involved, the more chance they will have to succeed and achieve improvements. It’s really not fair that anyone expects committees to do everything for them as the committees are unpaid and anglers too.
It was great to see a couple of youngsters turned up to help too. Struan took time to show one young man the drone and how to fly it. It think this will be at the top of his Christmas list next year.