Our Projects

Environmental

London Borough of Southwark

Herne Hill Flood Alleviation Scheme

After many homes and businesses in the Herne Hill area of London suffered millions of pounds of damage in the 2004 and 2007 floods, the London Borough of Southwark appointed Mouchel as lead consultant to carry out a feasibility study, scheme appraisal and detailed design services to better understand the area’s flooding conditions and implement a solution to enhance future protection.

The £4.28m project involved teams from across Mouchel and was jointly developed as a partnership between Southwark Council, The Environment Agency (EA), Thames Water and its contractor MGJV. Initially seeking to understand the current flooding mechanisms, we looked to devise and implement an innovative solution which would enhance future flood protection for the area, providing protection for some 400 homes.

A sustainable solution

Starting out as a feasibility study involving 2D hydraulic modelling – mapping and validating the results of the previous risk assessment studies – our teams were able to replicate known storm events, and predict future events and volumes of water. Responding to the client’s request to have a Sustainable Urban Drainage System (SUDS)-based approach, we then developed a solution which focused on potential flood risk in two Grade II listed historic parks and a local sports ground, based on topography and climate change.

The principles of the scheme involved gentle contouring within the parks to form earth bunds to temporarily store flows above ground with a total flood water volume of up to 45,000m3. This was combined with underground geo-cellular tanks and filter drains that provided effective drainage to the parks under all conditions – removing the need for expensive sewerage infrastructure improvements located within the road network.

Engaging the community

Working in two historic parks inevitably caught the interest of the community, with a need for an open and ongoing engagement process to be established from the outset. Our in-house landscape, consultation and engagement skills, as well as the engineering, modelling and other supporting services were key to this.

“Here is a project that has been bold in its conception that has literally walked the community through the issues; listening, learning and acting upon what has been learned as it went along. The legacy is a physical monument to what people can do to mould a sustainable urban environment and also a mental legacy in the form of a more educated and engaged urban community and we are very proud to have been part of it.”

Louise Wood, Chairman, The Burbage Road Residents’ Association

Completed in December 2015, we successfully used open spaces in areas such as Dulwich Park to store water in the event of an extreme flood (a one-in-seventy-five-year event) and provide protection for some 400 properties.

In addition, the scheme won this year’s Environment Agency (EA) award for Partnership Project Excellence demonstrating our award winning approach taken to deliver an innovative flood alleviation scheme in a complex urban environment with considerable local support.

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£4.28m

Cost of project

“This scheme has been a fantastic example of how strong partnership working and communication can deliver a vital flood risk scheme that not only benefits flood risk but also the wider community and environment.”

Mark Douch, Environment Agency Flood Risk Manager