The aim of this project was to create salmonid spawning riffles, improve floodplain connectivity, raise local groundwater levels and enhance the bio-diversity at the confluence of the River Gwash and Welland. This was achieved by creating a more naturally functioning river and floodplain.
Access to the site was through a public sports field and across a historic, former canal, track matting, a piped temporary gravel crossing and Heras fencing were utilised to minimise impact and ensure safe segregation from the public.
Simplistic, high level designs were developed onsite in close partnership with Chris French (Project Manager for Welland Rivers Trust), to maximise environmental gain.
The requirements of this project were to raise water levels and create a more naturally functioning river and floodplain, as cost effectively as possible. The two 20m long riffles required a total of 600t of imported stone to raise the dredged riverbed to its former level. The budget was not available to raise the bed for the entire length of the site, so a creative solution was required to deliver outcomes to the budget available.
Working closely with the client enabled us to harness local knowledge, experience and industry best practice to deliver a cost effective solution.
Site won hawthorn trees were hinged into the River Welland, the dense, entwined brushwood created a appropriate mattress ‘foundation’ in the 2m deep river. The steep, perched banks were re-graded down onto the brushwood, Excess bank material was transported away from the river and landscaped outside of the floodplain for tree planting. The gently sloping banks were covered with woven coir to minimise soil loss and are to be planted by volunteers in due course .
Appropriately installed riffles raised the river bed effectively, 600 tonnes of imported stone delivering similar results to the estimated 10,000 tonnes required to raise the entire river bed.
The project has been a massive success with lots of positive feedback from local residence and the client. The aims of the project have been achieved with a more natural floodplain and riverbed cross section. Following restoration, the site is now to be incorporated within an innovative Carbon Plus offsetting, wet woodland tree planting scheme.