£50M flood-defence scheme opens in Leeds

£50M flood-defence scheme opens in Leeds

A £50 million state-of-the-art flood alleviation scheme in Leeds, which uses moveable weir technology for the first time in the UK, has now opened.

The first phase of the Leeds flood alleviation scheme, delivered by BMMjv (BAM Nuttall and Mott MacDonald), uses state-of-the-art flood defence engineering techniques to create one of the largest river flood alleviation schemes in the country.

The scheme comprises three main elements: state-of-the-art mechanical weirs, the merging of the river and canal, and flood walls and embankments stretching 4.5km through the city centre.

It is the first time that moveable weirs have been used in the UK for flood alleviation purposes.

The new weir gates are supported by giant inflatable neoprene bladders that can be lowered when high river flows are expected.

It takes around two hours for the gates to lower and, thanks to the installation of these weir gates, it has been possible to keep flood defence wall heights to a minimum so as not to spoil views of the city centre waterfront.

The weirs have been installed at Crown Point in the city centre and further downstream at Knostrop, where a new locally manufactured bridge has been installed across the weir connecting the diverted Trans Pennine Trail with the north bank of the river.

In addition to these measures, the removal of a manmade island, known locally at Knostrop Cut, which separated the canal and river, has been removed to improve a bottleneck for flows.

Over 180,000 tonnes of material that has been excavated from the site has been reused on a local development site and also on diverting the Trans Pennine Trail which previously went across the manmade island.

Reusing this material has saved the project in the region of £6 million.

Project Manager for BAM Nuttall, Andy Judson said: “We’ve constructed two moveable weirs, one at Knostrop and one at Crown Point. We’ve provided 36 separate zones of the linear works up through the city centre.

“The projects main innovation are the moveable weirs, controlled by air bladders. This is the first time this has been used for flood alleviation in the country.”

“We’ve had a really strong ‘one team’ ethos on this project. We’ve all been co-located and understood that by working together, we would get the job finished on time and on budget.”

“We estimated that there are around 125,000 people who have live or work within sight of the project, so there are an awful lot of stakeholders and an awful lot of careful management that has gone into looking after people.”

Led by Leeds City Council in partnership with the Environment Agency, the scheme will provide more than 3000 homes, 500 businesses and 300 acres of development land with increased protection against flooding from the River Aire and Holbeck.

More than 22,000 jobs will be safeguarded over the next 10 years due to the increased level of protection and through the scheme’s development and construction, 150 jobs and apprenticeships have been created.

Leader of Leeds City Council Judith Blake CBE said: “We are delighted to see this much-needed first phase of the Leeds Flood Alleviation Scheme opened.

“As could be seen by the devastation at Christmas 2015, providing increased flood protection in Leeds is essential in terms of reassuring our residents and businesses, and this fantastic state-of-the-art scheme provides it for the city centre and downstream at Woodlesford.

“The clever use of the mechanical weirs is a brilliant idea, and they have also brought about environmental benefits with the improved river quality bringing salmon and otters, while the new bridge looks stunning offering great views of the river and beyond as part of the Trans Pennine Trail.

“We’d like to thank everyone involved in this phase of the scheme and look forward to developing the plans for phase two and beyond, as only through an entire catchment and citywide approach can we protect all communities in Leeds from the threat of flooding.”