The project in Morpeth will work alongside other flood protection measures to help protect around 1,000 properties in the town.
The scheme to build Cotting Burn dam was completed in May. It forms the last piece of construction on the joint Environment Agency and Northumberland County Council project.
Work to reduce the risk of flooding from the River Wansbeck in town defences were completed first, followed by the large upstream storage area at Mitford. This year, tree poles were installed into the river near to Lowford Bridge to prevent large debris from reaching the town centre.
-- Advertisement --
A separate £1m scheme by the county council to address surface water flooding at several locations in the town is underway and scheduled for completion by March 2018.
The Environment Agency's Alan Cadas, Operations Manager in the North East, said: "The Morpeth flood scheme is the biggest in the North East and boasts one of the largest flood storage areas the Environment Agency has ever built.
"But this work on the Cotting Burn is equally important and works together with the other features to ensure Morpeth is protected from both the burn and the River Wansbeck.
"This has been a great partnership involving local residents, who have played, and continue to play, a vital role in the success of the scheme. It shows that by working together with others we can create long term solutions to reduce the risk of flooding in our communities."
Cllr Glen Sanderson said: "We're delighted this major joint scheme to protect the people of Morpeth is now complete.
"This was a great example of agencies working together on a hugely ambitious engineering project and the fact it has already been used more than proves its worth."
(LM)
