Work has started on repairs to the Loyn Bridge in Gressingham, a scheduled Ancient Monument and Grade II listed building, damaged in the December floods.
The work, which will cost £600,000, is part of a £5m programme to repair transport infrastructure damaged in the floods, funded by the Department for Transport.
During the storms a large fir tree was carried down the river Lune and caught against the bridge piers which stand in the river.
The force of the floodwaters against the tree and the bridge itself gouged at the piers and damaged the stone.
Additional damage was caused to the bridge’s foundations, where the water scoured holes which need to be filled with stone.
This damage weakened the bridge to the point that it had to be closed for safety reasons, causing a long diversion route and inconvenience to local people.
County Coun John Fillis said: “The closure of the Loyn Bridge has been inconvenient for local people and I’m grateful for their patience and understanding during this period.
“Immediately after the bridge was damaged we put in temporary protection for the bridge’s damaged piers, which was necessary to prevent more damage from further flooding, which could have potentially swept the bridge away.
“We’re now able to remove that temporary protection and start work as we move into March and April, which historically have the lowest average rainfall.
“We have been working closely with Historic England and the Environment Agency about the repair work, and are hopeful that we will now be able to make good progress in repairing this historic structure, which still plays such an important role in the lives of local people.”
The bridge is expected to be re-opened to traffic in four weeks, depending on weather, although further work is necessary that will take an additional eight weeks, the county council said.
The first phase will see the reconstruction of the piers on which the bridge stands and the repair of its foundations.
A further piece of work will involve the removal of a gravel bank in front of the bridge which, if left untouched, would erode the river bank and the bridge foundations.
Work will also be carried out to protect the river bank from erosion.