Nature River Mel
Our last article concerned the planning and permissions process that we have to follow before we can start work in the river, but what happens next? What can one do to ‘restore’ a river? The problem with the Mel is that it has become over-wide and its naturally stony bed has become covered with a deep layer of silt. Here we explain some of the restoration techniques that we have used to enhance the river and its flow. We have used the following traditional ‘soft’ engineering techniques:
Revetments edged with faggot bundles We managed to source a supply of pre-made bundles of hazel faggots approximately 2 metre in length. We initially used these to support the coir rolls as described above, but we also tried using these alone to create the front edge of the revetments. As it has turned out, this last method has proved the most easily installed and the most cost effective method for us. Another method that we have used in places in Meldreth, but not in Melbourn, is that of woven edged revetments or ‘spilings’. Here stakes are hammered at intervals into the riverbed and then the front edge is woven with locally freshly cut willow witheys or hazel poles. The revetments are then back-filled with brashings and silt in similar manner to those edged with faggot bundles. Riffles The riffles were constructed using gravel that had been sourced with the help of the Rob Mungovan, the Ecology Officer, and it was chosen to so as to match as closely as possible the naturally occurring stone found on the riverbed. We are grateful to Dr Ian Hirst and Rob Mungovan for the help and advice they provided with regard to the installation of the riffles. Filling & Planting We have trialled a number of methods of filling and planting the new revetments • To do nothing, and wait to see what happens • To fill with a specially sourced gravel/hoggin mix & plant • To fill with silt and plant
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