Nature River Mel Restoration
In the last issue of the Melbourn Magazine we reflected on the early days of the Group. As we said, the planning stage was time consuming and frustrating for those members who so desperately wanted to start the in-river work. Initially we did not really know what we had taken on, and even now there is a lot of work behind the scenes that needs to be done to enable the practical in-river sessions. Our aim was to improve the biodiversity of the river from the ‘bottom up’, so that our project would benefit the whole food-chain. For this to happen it was crucial to speed the flow of the river so as to clear the silt and reveal more of the naturally chalky riverbed. This we planned to do by installing structures to narrow the river, called revetments, but these needed to be constructed from natural materials that were sympathetic to the needs of fish, small mammals (particularly water voles) and other wildlife. We also planned two riffles (shallow areas of gravel) to provide enhanced breeding grounds for the few remaining brown trout in the hope that they would colonise the river again. Before we could start, we needed to obtain Drainage Consent from the Environment Agency for our project. Drainage Consent is akin to obtaining Planning Permission if you want to build or alter a house, so we were just a little daunted. After consultation with Rob Mungovan, South Cambridgeshire District Council’s Ecology Officer, a detailed scale plan, incorporating each of the structures that we intended to build, was produced using electronic mapping templates from Ordnance Survey. This, along with the rest of the application documents, was then submitted to the Environment Agency for approval. This consent is by no means automatic, so the next stage, a site visit by one of their
Officers, was followed by a nail-biting wait on our part. In order for us to better understand what we were taking on, Rob also arranged for us to visit the RSPB nature reserve in Fowlmere to see the similar restoration works taking place there. This was followed by two of our committee members getting their feet wet for the first time when they joined Rob ‘in the river’ at Fowlmere to gain first hand experience of the techniques that we intended to use on the Mel. Rob had advised that we use traditional ‘soft’ engineering techniques that would have low impact on the environment and could be readily removed if necessary. The first of these was to use pre-planted coir roll to form the front edge of the new revetments that we used to narrow the width of the river in selected places. These were supported by 2-metrelong bundles of hazel rods, known as faggot bundles, which were staked and wired into position to stop them being washed away. The revetment was then back-filled with brashings (a collective term for tree pruning’s), which, in most cases were held in place by cross-logs that were wired into place to form a firm ‘mattress’. Coir is a coconut fibre that is densely packed into netting to make rolls of a similar size to the faggot bundles. The commercially produced coir rolls seemed like a really good idea at the time, providing both support to prevent erosion and enabling bankside planting of native species all in one go. Unfortunately, the best plans sometimes go awry; the coir washed out of the netting and the plants died! After further talks with the experts we decided to use extra faggot bundles, backfilled with brashings and silt, instead of the coir rolls. We then planted the revetments with native plants that we had grown in our own waterside nurseries. Fortunately, this technique has stood the test of time, proving, on this occasion at least, that simple methods are often the best. melbournmagazine
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