Work is underway on a floodbank upgrade to protect Dunedin Airport and thousands of hectares of highly productive farmland from flooding.

The $5 million upgrade is focused on the Contour Channel floodbank on the Taieri near Mosgiel, which was originally built in the early 1900s.

The Otago Regional Council said the upgrade was the biggest package of work within its climate resilience programme.

Project delivery team leader Brett Paterson said the floodbank would intercept runoffs from streams on the Maungatua Range and direct the water into the Waipori River.

Building is due to be completed in 2025.

The project was co-funded by the government after the council receiving funding as part of the 2020 Budget.

Otago has seven flood schemes that protect roughly 43,000 hectares with 218km of flood banks, 14 pumping stations, and 55 bridges.