Flood prevention schemes for London parks

Case study Flood prevention schemes for London parks

At Metis, our environmental and civil engineering team work closely with councils across the UK to help them improve natural environments and mitigate flood risk in the most sustainable way possible.

The London Borough of Hillingdon approached us for design work on a series of flood risk management projects in local parks. This led to us eventually managing the construction of these designs.

Having worked with them before on highways and water projects, we already had a great working relationship with them, so getting started was easy.

If you’d like to learn more about our flood risk management schemes for Hillingdon Court Park and Elephant Park, just keep reading!

The challenge

Hillingdon Council tasked Metis with correcting surface water flooding issues in local parks. The two parks experiencing major problems with flooding were Elephant Park and Hillingdon Court Park, two popular green areas for local communities.

The flooding was caused by capacity issues in sewers downstream of the parks. The sewers couldn’t handle the amount of water passing through them, especially during significant rain events, leading to excess water spilling into the parks and people’s gardens.

These floods were not only causing property damage to local residences, but they were also impacting local communities as they couldn’t use the parks as normal. The floods meant that sports teams had to cancel matches, and walking through certain areas was unsafe.

The solution

Metis designed and worked with a contractor to manage the construction of sustainable drainage systems, including a large open drainage channel scheme, basins, and embankments in these parks. These sustainable systems were used instead of traditional hard-engineered concrete pipes (bad for the local environment) with new sustainable open drainage channels.

Elephant Park

In Elephant Park, this scheme took water out of the surface sewer system and built a long meandering swale (an open drainage channel) ending in an existing pond. The meandering shape allowed water to spend more time in the channel, alleviating stress on the sewer and creating capacity outside the sewer system.

We also built several wildflower mounds using excavated soil, before organising a local community planting day, which would see flora and foliage grow on the banks along the pond.

Hillingdon Court Park

In Hillingdon Court Park, we built concrete steps (or weirs) within the channels to slow water flow, relieving pressure on the sewer downstream. This means water stays in the channel longer, adding to aesthetics.

In this park, we also constructed ponds, channels, and embankments to hold back water long before it goes back into the sewage system.

Instead of taking the excavated dirt off-site, which would have carbon emission and cost implications, we built wildflower mounds from several hundred cubic metres of soil, making the perfect environment for planting with the local community.

The results

Getting the local community involved in the planting schemes gave them a sense of ownership over the parks and helped us to secure community buy-in for the flood prevention schemes.

Ducks are already enjoying the new ponds in Hillingdon Court Park, landing in only two weeks of the ponds being filled with water. Other wildlife and organisms are benefiting from the newly planted banks.

The primary aim of this project was to reduce flooding to surrounding residential properties.
We were able to introduce a sustainable solution to this issue while enabling all the benefits listed: enhanced biodiversity, protected local ecology, improved green spaces, and a more sustainable flood prevention system for these local communities, all without impacting the use of the park.

Overall, the client was pleased with both schemes, as we achieved them within the expected deadline and under budget and had excellent feedback from the local community.

Explore more work by the Metis team

Want to learn more about our work? Check out some other Metis case studies.

If you’re looking for an experienced, passionate, and innovative civil and environmental engineering team to partner with you on your next project, please get in touch with us today.

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