A £50 million flood alleviation scheme in Leeds which uses movable weir technology – a first for flood risk reduction in the UK – was opened recently by Chair of the Environment Agency, Emma Howard Boyd.
Led by Leeds City Council in partnership with the Environment Agency, the Leeds Flood Alleviation Scheme will provide more than 3,000 homes, 500 businesses and 300 acres of development land with increased protection against flooding from the River Aire and Hol Beck.
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 center.
It is the first time that movable 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 defense wall heights to a minimum so as not to spoil views of the city center 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. 180,000 tonnes of material 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.
The earlier stages of the scheme included work at Woodlesford further downstream, which were completed in 2015 and proved effective during the December 2015 floods.
A consultation on the second phase of the Leeds Flood Alleviation Scheme is now open until 16 November, to provide increased flood protection to communities upstream of the city center. Proposals include measures further upstream including the Kirkstall corridor which was badly hit by the floods as well as Stourton, an industrial area that was badly affected on Boxing Day 2015.