Officials are urging Aucklanders to take advantage of the calm before the next storm to check drains on their street for any blockages.
Despite record-breaking rainfall at the weekend leaving much of the city underwater, there is still more to come later on Tuesday - with a red warning from MetService for northern regions, and orange for everything south of Orewa.
"It is going to be widespread heavy rain," meteorologist Lewis Ferris told Morning Report. "We might see hourly totals around that 40mm mark. If that is falling on top of what might have been six or seven hours of persistent rain, that's when we really see those impacts come about."
With much of the city still soaked from the weekend's downpour, it wouldn't take much to trigger more flooding, experts have advised.
"Our biggest area of concern is the fact that we are already water-soaked, as a region, and we are about to get more," Auckland deputy mayor Desley Simpson told Morning Report.
"That in itself means that it's not just a one-off - it comes on top of the water we had at the weekend. That's our biggest concern."
Desley Simpson, second from left, attends a flood briefing two days ago with mayor Wayne Brown. Photo: Supplied
Parks become temporary lakes
Many parts of Auckland performed better than expected thanks to what planners call "invisible infrastructure" - wetlands, grassy areas and streams which are intentionally designed to flood in ways that keep water away from houses.
Auckland councillor for Albert-Eden-Puketapapa ward Julie Fairey said in her part of the city, Keith Hay Park "turned into a lake" - as it was designed to do to prevent nearby houses and businesses taking on water instead.
"As we build more impermeable surfaces like concrete in our city, we actually need to balance that with more permeable surfaces, which in the urban area look like berms, look like rain gardens, look like parks.
"A lot of our sports fields are actually designed to be flood plains in extreme events, and we saw that happen in the last few days."
To give the city's waterlogged infrastructure a hand, Simpson said people should pop outside sometime today to check leaves, twigs and other debris aren't blocking stormwater drains.
Longer-term, Fairey said the Central Interceptor - a massive $1.2 billion wastewater tunnel currently being constructed under the city - will also help.
"Although it's a wastewater programme, not a stormwater programme, if we can have fewer wastewater overflows - which the central interceptor will help with - then we'll have less wastewater getting into the stormwater in these bad flows.
"And people absolutely have to stay out of the water - there's poo in it. It's flooding to our rivers and harbours and bringing poo through the stormwater into those places as well."
Wind a worry
Simpson said emergency services are ready for the upcoming rain, having had "a bit of practice" in the past few days. An added worry this time around though will be strong winds, with MetService warning of potential gale-force winds in the city.
Simpson said she is concerned trees will be blown over onto powerlines and homes.
"We have all emergency services on standby, we have our evacuation centres open and more are planned if needed. The mayor has also asked the government to make sure the army is ready if we need them…
"So I think yes, we're as ready as we can be. Schools are closed, people are urged to stay home. Be vigilant, be prepared."
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