Challenge

Tilgate Park, a natural leisure facility within the growing Borough of Crawley, attracts hundreds of thousands of visitors each year from South East England.

The Environment Agency identified the need to reduce the incidence of flooding along the River Mole in a plain extending as far as London Gatwick Airport. As well as being a natural amenity, Tilgate Park features a dam that serves to attenuate flow and, in doing so, mitigates the potential for downstream flooding.

With a fast-growing conurbation and corresponding increases in surface water run-off the dam’s capacity required re-evaluating. As a result, the need for more storage was identified, and a realisation that the boundaries of the existing reservoir could not be extended. To accommodate this an increase the depth of storage by raising the dam crest was decided upon.

Solution

Grasscrete was used as a paving layer at the site in a previous project to improve access to the park's tracks and car parks. This latest project highlighted Grasscrete's capabilities within a water environment.

As part of the works Grasscrete was selected to enforce the spillway slopes as well as the stilling bays around the outfall. Grasscrete GC2, with a thickness of 150mm, was chosen for its ability to accept flows of up to 8m per second, and for its flexibility to follow changing plan and contour profiles without compromise in performance.

Outcome

On completion the works quickly harmonised with the natural forest environment that surrounds the reservoir.