Some red-zoned areas of Christchurch along the Avon River could end up being turned into wetlands.
Several sections next to the river in the eastern suburbs have sunk and flood every time there is a high tide since a devastating earthquake in February.
The Christchurch City Council has built stopbanks and put out sandbags to prevent severe flooding in the short term.
In the long term, it says the plan is to fix the pipes and drainage issues in the green zone where people will still be living.
In the residential red zone the council is proposing to relocate the roads away from the Avon and let it rise into a natural wetland.
Meanwhile, the Avon flooded around some of the worst quake-affected areas of the city again overnight on Thursday, forcing some road closures.
The council says the river is expected to flood several more times over the next few days due to high tides and a low atmospheric pressure over the country.