The BART team have been busy working away to improve the habitat for wildlife along the River Marden and Abberd Brook in Calne.
Following the small weir removal at Castlefields Park last winter, our delivery team has been working in partnership with Friends of the Marden Valley and Calne Town Council to install two flow deflectors in the River Marden back in September.
BART, alongside a team of enthusiastic volunteers, created two brushwood berms that were tightly bound and secured to the riverbed to create ‘pinch points’ in the channel. These where strategically placed to narrow the channel and input small meanders into the river where the channel was previously over wide because of the weir. The brushwood berms will help to restore natural processes to the river system, creating areas of scour and deposition, allowing the river to ‘look after’ itself. They will clean gravels (very important for trout spawning) and increase biodiversity by creating different microhabitats within the river, with each supporting a different assemblage of wildlife. The flow deflectors are set at summer flow levels and designed to overtop in high flow conditions, and eventually will fill with sediment as river levels subside.
In October the BART team was back to complete a small river restoration project along the Abberd Brook in Calne, adjacent to the riverside footpath popular with dog walkers, joggers and local residents. The brook has been artificially straightened and in places over-widened, causing slow flows which has resulted in the riverbed becoming a silty and unsuitable for many invertebrates and aquatic life.
BART and volunteers from the Friends of the Marden Valley installed 4 brushwood berms constructed from wooden logs and brushwood to help improve flow and water quality conditions. These brushwood berms will help to create a more diverse river cross section and material that is scoured will be naturally deposited downstream to create shallow riffles. This material will form valuable habitat for marginal plants to colonise as well as providing habitat for fish and invertebrates. The enhanced flow diversity will also improve the river’s ability to deal with low-flow conditions.
Thank you to Calne Town Council, Wiltshire County Council and Bowood Estate for providing permission to undertake the work and to The Halpin Trust and the Friends of the Marden Valley for funding this project. A big thank you to volunteers of the Friends of the Marden Valley for their valuable support with both projects.
For further information on this project, please contact Nick@bristolavonriverstrust.org