The Office of Public Works is defending its flood relief plans for Cork city as the only viable way to protect against flooding.
It comes amid mounting public concern that the €140m flood defences could cause huge disruption and increase the flood risk during its construction.
The Save Cork City group is urging the OPW to look at how countries like the Netherlands have moved away from the traditional approaches.
Ecologist Anja Murray, author of a report on natural flood management for Friends of the Earth, said: "What we need to be doing is holding flood waters back, higher up in the catchment.
"And that's looking at peatland restoration, woodland creation, managing agricultural land, looking at development in flood plains, and rehabilitating flood plains.
"It's about enhancing the capacity of the landscape to hold back floodwaters so we don't have to rely on hard engineering solutions."