The scheme, which will see the construction of a new flood storage basin and a pumping station at Keswick, will begin on Monday.
Cumbria County Council said contractors were determined to keep disruption to a minimum.
Keswick Flood Action Group said it was relieved the scheme was going ahead.
The county council said the Penrith Road area "forms one of the greatest areas of surface water flood risk in the county in terms of scale, frequency and impact on the local community".
Councillor Keith Little, cabinet member for highways and transport, described the scheme, which will cost about £2m, as a "significant investment".
He said: "A lot of detailed background work has been carried out behind the scenes to understand how and why flooding tends to be more devastating in the Penrith Road area than other parts of the county."
Mr Little said the work "will protect hundreds of properties from future flooding events, and stop the extent of surface water from disrupting the surrounding highways and local businesses".
Penrith Road will be closed for 14 weeks while the work takes place