Dunsbury Park Riverbank Flex MSE Retaining Wall – 2016

Case Study: Riverbank/Retaining Wall, Dunsbury Park, Havant, Hampshire, PO9 4EE, UK

Client: Portsmouth City Council

Designers: Peter Brett Associates

Contractor: VolkerFitzpatrick

As part of a commercial highway scheme to redevelop land on Dunsbury Hill Farm, Havant, consulting engineers Peter Brett Associates designed a permanent, green solution to create a riverbank alongside a new link road between the B2150 and the new Dunsbury Park site. Flex MSE® Vegetated Wall System was specified to preserve native habitats and ecological features, as well as diverting an existing stream to provide wetland for wildlife and increased flood alleviation capacity.

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VolkerFitzpatrick, the winner of the tender, installed Flex MSE® GTX Bags & Interlocking plates, reinforced with geogrid, alongside rock-rolls & gabion baskets.

Flex MSE® Units, prefilled with a free draining granular material (first two courses) and a proprietary mixture of sand & compost (remaining courses) were installed up to 2m high, with geogrid laid every three rows tying up to 1m into the bank. Some of the Units were filled with a pre-seeded mix. Posts and a safety rail were installed alongside a public footpath that was created at the crest of the bank.

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The Units were then hydroseeded using a native seed mix, and within 12 weeks were fully covered in vegetation.

The project was completed in a matter of weeks, required very little machinery to install as the Flex MSE® Units were delivered prefilled to site, and installed by hand, without any heavy machinery required. Twelve months post-installation, the system was completely covered in vegetation, and had blended into the natural environment.

The Flex MSE® GTX bags are both water & root permeable and UV-stabilised, acting as a scour protection at the face, withstanding high flow-rates during flood events.

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