The Arup & Nuttall for the Environment Agency: Wakefield Flood Defence Works

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Wakefield has suffered from over a century of severe flooding from the River Calder, causing widespread damage to the area. In response, the Environment Agency commissioned a £7 million contract as the first phase of a flood alleviation scheme, with emphasis on measures that would be sympathetic to the town’s local environment. The Wakefield design and build scheme protects more than 1,000 properties and major infrastructure in the city centre. It is one of five projects awarded to Arup, in collaboration with Edmund Nuttall Limited, as part of the Combined Capital Works Project 2.

The works comprise 10 kilometres of flood defences through Wakefield and the creation of upstream flood storage reservoirs or ‘washlands’. The washlands create recreational and habitat improvements, and by storing water, reduce the flow downstream, meaning the new defences can be built to a smaller, less intrusive scale. ‘Soft Engineering’ and innovative design were encouraged. The scheme incorporated ‘green’ erosion protection; use of reinforced earth embankments instead of walls; and altered alignments and design solutions to preserve habitat. Environmental enhancements included a floating tern island, an otter holt, washland shallows, and the planting of native trees.

Historic buildings were integrated into the defence: Fall Ings Lock was raised to flood defence standard and internal improvements were made to Hirst’s Mill to ensure it was better protected from flooding. In both cases existing copings were retained and/or reused. The defences are designed to aesthetically interact with existing buildings and structures and included public art to reflect the heritage of the city.

The Environment Agency set sustainability targets including 20% waste reduction, energy saving, recycling, and use of FSC (Forest Stewardship Council certified) timber. By incorporating 'lean' design methods the team cut waste by nearly 90%. Additional energy saving measures included engineers and site visitors using bikes instead of cars to travel around the construction sites.

At all stages, the team consulted with stakeholders through public meetings, flyers, notice boards, and a website. The local community was also addressed: access tracks, footpaths and bridleways were preserved or enhanced; visits were made to local schools to lecture on the dangers of construction sites, and the team competed and sponsored fund raising events to raise money for Wakefield Hospice.