Auckland Council says managed retreat is "on the table" for the highest-risk parts of Tāmaki Makaurau in the future.

Auckland Council's head of planning for healthy waters Nick Vigar told media this afternoon that "a whole bunch of people for the first time ever are finding out that they live in a flood plain or...an overland flow path".

Overland flow paths are the routes taken by water when the man-made drainage network is overloaded, the council website explains.

Warning "there will be more events this big or bigger", Vigar said: "You can never design a pipe network to cope with every rainfall event that will fall, that's just a fact of life."

He said that, when new developments are being built, those overland flow paths can be engineered away from critical infrastructure.

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"Contrary to that is the case of already existing urban development," Vigar said.

"Just to give you some broad numbers...somewhere around 50,000 properties in the region sit in a 100-year flood plain and something like 55,000 sit in an overland flow path."

Vigar said the key thing for property owners to understand is whether they are in an overland flow path, so they can plan effectively by removing fences that block the path, removing debris from the path and potentially recontouring the path around the property.

For flood plains, the scenario is more difficult, Vigar said: "A flood plain is going to flood."

People who live on flood plains are advised to raise buildings if possible, ensure safe exits are available and plan for future rain.

For people on flood plains who are rebuilding, Vigar advised not using basement levels as habitable floors, not carpeting basement levels, using resilient internal linings, raising power points and not storing things on the floor on basement levels.

"People have to understand that this event will happen again," Vigar said.

Auckland Council's head of healthy water strategy Andrew Chin added that the council "haven't considered red-zoning areas exposed to flood risk at the moment" but "we're getting into the zone of considering, should managed retreat happen" from the highest-risk areas.

"It does need to be considered...that for those very high-risk areas, it needs to be an option on the table."