River works planned to protect Northumerland road from erosion
Plans have been lodged for works on a stretch of a north Northumberland river in a bid to protect the nearby road.
The application, which has recently been submitted to Northumberland County Council, relates to two sites on the River Breamish to the west of Brandon.
The proposals are by the River Till Restoration Strategy (RTRS), a partnership project between the Tweed Forum, the Environment Agency and Natural England which ‘aims to protect and improve the Till river system in areas not achieving their potential conservation value’.
A design document states: ‘In the upper part of the Till catchment, the River Breamish between Brandon and Ingram has a history of riverbank erosion that threatens to undermine the public highway on the left bank.
‘This reach of the river is a high-energy, dynamic gravel-bed system and as such, the river is prone to lateral movement, particularly during flood events.’
It goes on to explain that in its current position, the river is sandwiched between the high ground of East Hill to the south and the highway to the north, with a possible long-term solution being to re-route the road and allow the river to move within the floodplain.
In the past, short-term solutions such as boulder riprap (rocks placed to protect the riverbank) have been used, but ‘in many places the boulders have been undermined and washed out’.
What is being proposed now is a medium-term solution, using what are described as soft engineering approaches; the strategy says that ‘these methods are less likely to increase energy and erosion downstream, are less prone to being undermined (as they are held into the riverbank laterally), and provide morphological and ecological diversity due to the rough texture’.
At the westernmost site, where the riverbank is seven metres from the road, a technique called root-wad, which involves inserting felled trees on their side into the bank with the intact roots sticking out into the water and riverbed, would be used.
At the site nearer to Brandon, the bank is just five metres from the road, which ‘could be undermined in the next large flood event’ following significant ‘erosion, deposition and associated channel migration’ in the last decade.
Here, it is proposed to install a log-matrix design that uses posts arranged to mimic the protection provided by a natural dense stand of trees.
At both sites, there will be planting of native tree species on the reinstated banks to help bind them together and increase the stability.