Work to replace a bridge on the route of a planned artificial river in Oxford has begun.
Last year, inspections revealed repairs to the A423 Kennington Railway Bridge were no longer viable.
Oxfordshire County Council said work had begun to prop up the underside of the bridge, which is on the route of the Oxford Flood Alleviation Scheme.
The authority said the new £40m bridge and £150m flood scheme were now being designed and built together.
Archaeological survey trenches are also being dug in a field close to the A34 at South Hinksey, where workers on the scheme could be based.
The project, which has been delayed due to the bridge works, will eventually see a stream created to the west of Oxford, with the aim of taking rainwater off the fields and preventing flooding.
By designing and building both the bridge and flood alleviation scheme together, the county council said it would enable it to "reduce disruption" and "ensure the best use of public money".
The updated design will use open channels instead of culverts to allow the flow of floodwater under the bridge, the authority added.
The council hopes to replace the bridge in the autumn, with some road closures planned, including on junctions which leave the bypass.
Significant floods in recent decades have caused damage to homes and businesses and closed the main railway line and major roads.
The scheme is being created by the Environment Agency, Oxfordshire County Council, Oxford City Council, Vale of White Horse District Council, Thames Water, Thames Regional Flood and Coastal Committee, Oxford Flood Alliance, Oxfordshire Local Enterprise Partnership, University of Oxford and Highways England.