South Australia has launched a $140 million flood mitigation plan for Adelaide.

The State Government has signed a deal with five local councils for a 20-year project to flood-proof Adelaide's inner-south and south-west.

The government says the flood mitigation works in the Brownhill and Keswick Creek catchments will reduce the effects of a one-in-100-year flood event by 98 per cent.

Floodwaters inundated several properties in Mitcham and further downstream in Adelaide's inner-southern suburbs late last year, after more than a decade of warnings that the area was susceptible to flooding.

“We have been working for the best part of 10 years to mitigate these issues, and put the plan in place,” Water Minister Ian Hunter said.

“Work has been ongoing in infrastructure in this area for 20 years or so. Bringing it altogether under one management plan in the Stormwater Management Authority, this is a breakthrough.”

The plans involve the councils of West Torrens, Unley, Burnside, Mitcham and Adelaide City.

Mitcham Mayor Glenn Spear hopes the Federal Government will get involved in the project.

“I have some concerns about the 20-year timeframe for implementation,” he said.

“We have residents in Mitcham, in Hawthorn, that have been subjected to major flood events two or three times over the last year or so.”

The State Government is funding 50 per cent of the required works, which will not include a previously proposed detention dam on upper Brownhill Creek.