Water wheel barrage concept could solve River Severn flood challenge

The proposal involves building a 800m long barrage across the Severn at Sharpness – the ideal location, according to the project’s inventors – to prevent tidal flow upstream in a bid to allow flood water time to dissipate.

The concept is the brainchild of former Atkins head of technology for floating structures Rod Rainey and Severn River flood expert Simon Hopkins who say using the barrage to generate electricity could make it self-funding.

“The End to Higher Flooding scheme is a modern version of a water wheel which can be used to generate electricity and pump flood water away,” said Hopkins. “On the River Severn the tide pushes water upstream which does not have time to return before the next incoming tide. This is repeated with rising tide cycles and prevents floodwater from dissipating.

“There is a 38km long channel in the river between Gloucester and Sharpness, so what if that area, which covers 26km² was empty of water ahead of a flood event? Our analysis shows that that capacity would allow flood flows to dissipate three times faster and would break the cycle of economic damage from flooding upstream.”

The steel water wheels would be 30m in diameter on the River Severn and be built in 50m sections on land that would then be floated out into position and rock anchored into place. The wheels would rotate slowly – 1 revolution per minute – which Hopkins says would be slow enough for fish to pass unhindered.

“The sections could be taken out and floated to land for maintenance,” he explains. “The design uses 30% less steel than conventional water wheels and no concrete, which make it an environmentally sound solution.”

The 50m wide wheels would be floated out into position and rock anchored in place

Hopkins estimates that the project would cost £100M to £200M to build and using the wheels to generate electricity when pumping out floodwater means that it could pay for itself in three to five years. He estimates that the project could be built within a year.

“We believe that the barrage would need to pump out flood water for 36 days a year,” said Hopkins. “Currently flooding issues affect towns upstream for up to six months because the water simply can’t get away.”

Hopkins said that details of the concept have been sent to the Environment Agency, local authorities and MP in affected areas and is hopeful that they will help drive the project forward. He describes the solution as a “no brainer” and said the reception to the innovation had been positive so far.

“The beauty of this design over a convention barrage is that it can pump out, as well as hold back water,” he said. “I think this is a game changer.”

According to Hopkins, a similar system could be used in other tidal rivers such as the River Parratt to protect the town of Bridgwater and the Somerset levels, and could also be scaled up to provide a replacement for the Thames Barrier.

Like what you've read? To receive New Civil Engineer's daily and weekly newsletters click here.