Salix was approached to find an ecologically sensitive design approach to replacing tradional gabions and blockstone along a stretch of the River Exe.
Salix’s pre-filled Rock Mattresses fit the bill perfectly.
This approach was found to be cheap and quick to install and resulted in robust slopes and a natural profile. This was required as the tidal nature of the river reduced the working time to one week in every four.
The Rock Mattresses also provide valuable habitat for invertebrates. This encouraged wildlife to thrive without losing the mattresses proven ability to stop erosion in this very dynamic environment. Mullets were found feeding off the banks within a month of installation, a crucial factor as this stretch of river is important for fishing.
The Flood Protection project
As part of the second phase of the Exeter Flood Protection works BAM Nuttall installed a new flood compensation area. The original design was modified, reducing the quantity of block stone along the waterline by installing Salix’s 250mm deep pre-filled Rock Mattress.
There was a site visit by the Environment Agency and the client’s engineer to inspect the work which they found very impressive. They were all full of praise for the fantastic result and the fisheries officer was ecstatic at the sight of the mullet.
BAM Nuttall worked with Salix to achieve savings in time and money to install the system and for the client it also delivered habitat and environmental value. The impressive results have been widely acclaimed. You can read more about the work on the Exeter Flood Defence Works.
Dr Ruth Callaway of Swansea University talks about the wildlife benefits of Rock Mattresses.