Grange Paddocks Weir Removal Feasibility

Location: Grange Paddocks, Bishops Stortford, Hertfordshire                                                          Client: Hertfordshire County Council

The River Stort is a chalk river which is an important yet rare and threatened habitat in the UK. Chalk rivers are mostly fed from groundwater and so the water they contain is often clear. Such rivers are typically diverse and contain many different types of insects and aquatic plants, including water crowfoot and types of watercress. Learn how we worked on behalf of Hertfordshire County Council to identify measures to improve the ecology of the River Stort at Grange Paddocks, Bishops Stortford.

Challenge

The ecology of the River Stort running through the grounds of Grange Paddocks Leisure Centre in Bishops Stortford is not as diverse as it should be, due to the weir at the downstream end of the site. The weir prevents sediment from being carried downstream. This sediment clogs important gravel habitats in the river bed, stops fish and other river life from freely moving up the river channel, and reduces the variety of habitat upstream. Fortunately, the weir is the last structure on the River Stort causing such negative environmental impacts. As the weir is limiting the health of wildlife populations, any costs to repair and maintain it in the future would not be justifiable.

Solution

We mobilised a team of technical specialists to site, to develop an understanding of the condition of the existing weir structure. Our aim was to establish a robust baseline of the ecology and geomorphology of the river corridor, both upstream and downstream of the weir. We also carried out  a desk-based assessment of the history of land use of the immediate area and the catchment upstream, to supplement our understanding of the site. This environmental baseline was drawn together and used in development of the conclusion: that weir removal would be the most appropriate solution to deliver sustainable improvements to longitudinal connectivity and in-channel habitat.

Grange Paddocks weir, River Stort
Grange Paddocks weir, River Stort

Benefit

We made efficient use of an existing topographic survey to reduce the costs of such data gathering before feasibility was confirmed. Our heritage and contaminated land specialists worked closely together to identify historical land use constraints that could be avoided by taking the approach of weir removal. Our hydraulic modelling team identified that there were flood risk benefits within the boundaries of both residential and amenity landholdings, in removing the weir.

Want to know more?

Email Jon Whitmore for more information about our work on Grange Paddocks weir removal feasibility, on behalf of Hertfordshire County Council.

You can learn more about our Environmental Services on our webpages.



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