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Data published by Earth Sciences New Zealand last year shows there are already 750,000 people at risk from a major rainfall or river flooding event. That number will rise steadily to more than 900,000 with 3°C of additional warming.
Allow water to move around property
What it is possible to do in many cases, though, is encourage the water to move around, rather than through your house.
“People are quite tempted to try and stop the water coming onto their property,” Brown says.
“[But] it’s going to keep trying to find the lowest point in the terrain to flow down, and so you must allow the water onto your property where it’s entering, and it’s got to allow it to exit when it’s exiting.
“Your job, as a homeowner, is to try and help the water get from one side of your property to the other without causing you damage.”
Although people are quite tempted to try and stop the water coming onto their property, it’s going to keep trying to find the lowest point in the terrain to flow down. (file image)
Unsplash / Wes Warren
Brown and his colleague, Nancy Baines, told RNZ gutters should be clear of leaves and downpipes need to be securely connected to gutters at the top and drains at the bottom, to stop water pooling or back-flowing into the roof cavity.
Where you store precious things and assets
There may be no way to stop water coming inside a house, Baines says.
That’s where preparing well in advance can help limit the damage.
“[There are] really easy things that anybody can do – it doesn’t matter if you’re renting, doesn’t matter if you’re on a budget – and that is where you’re storing things.
“All of your like precious things, high up, not just your electronics and your expensive things, but your family photos – what is the stuff you’re going to really miss if it’s damaged?”
Another easy thing that anyone can do, if bad weather is forecast, is to move cars parked in low-lying garages or dips in the street uphill beforehand.
Move cars parked in low-lying garages or dips in the street uphill beforehand. (file image)
Unsplash / Wes Warren
“For many of us and many renters, your car is your biggest asset – it’s what gets you to work, it’s what helps drop the kids, and losing that is huge.”
The Building Research Association (BRANZ), together with councils and universities, has been researching how people can limit flood damage inside their homes.
Senior materials scientist Katy Stokes, advocates lifting up what you can – appliances, cabinetry, and even electrical outlets.
“Things like kitchens and bathrooms are notoriously expensive when you do a renovation, and the same happens if you’re flooded and those need to be replaced,” she says.
What might obstruct water in your yard
Flood hazard maps published by many councils, including Auckland, can now help people spot overland flow paths, Brown says.
It’s also possible to just look for the high and low points, and avoid placing any obstacles in that path, he says.
“If you build, if you put a structure, any kind of landscaping that can obstruct the water, it can then either direct the water into your house or it can stop the water flowing past your house and it can build up.”
Look for the high and low points, and avoid placing any obstacles in that path. (file image)
Unsplash / Wes Warren
Raised garden beds, sheds, decks and even large pot plants can all be culprits.
“There’s some properties that are always going to flood, and others that might flood depending on your decisions.”
Brown points out a fence running across the bottom of the garden.
“If it was a solid fence it would impound water, and so water would build up behind it – and if it builds up high enough, then it can flood back through a home.”
That was something both of them witnessed after the January 2023 floods, Baines says.
“We had properties that flooded inside that wouldn’t have flooded if they hadn’t had a solid obstruction on the downstream side.
“Something else that we observed was those solid fences, the water building up so high behind them that the fence then catastrophically failed and collapsed, and caused a really big wave over the property below with all that extra energy, which was really damaging.”
It might not be necessary to replace an entire fence, Brown says.
“You can do something pretty easily – you just want an opening at the bottom of your fence. Some people find that difficult with dogs and trying to contain them, but something like having chicken wire along the bottom to keep your dogs in that lets the water through is a great start.”
