Do you know why we are experiencing about four times as many floods a year – and why the cost to consumers and the country has skyrocketed?
More to the point, do you know there are steps you can take that may help you assess the risk of flooding coming to your door?
After looking at modelling and speaking to the experts, here are the top five facts not commonly known about flooding in Aotearoa:
1. Floods are becoming more common…
Any national or regional history will tell you that floods – from the catastrophic to the mildly inconvenient – have long been an unavoidable condition of life here. Science suggests they'll have an inevitable impact on our country in the future too.
Floods are one of New Zealand's most frequent natural disasters. The number of floods that hit Aotearoa in a year has been steadily increasing since the mid-1970s. It used to be common to have one or two floods a year. Now, it's around four to seven, according to the Insurance Council of New Zealand.
That's partly because of more dumps of heavy rain and gnarly storms. The number of floods is set to go up even more in future, thanks to ol' mate climate change. A warmer atmosphere can hold more water – dumping it into rivers that then overflow or onto streets where it collects.
2.…and more extreme
We're not just experiencing more floods; they're worse – think more extreme rain and storms and bigger, stronger, faster floods.
One of the culprits behind intense flooding is atmospheric rivers – long, thin-shaped storms that bucket two to three times more rain than a regular storm. It was an atmospheric river that hit the West Coast in 2019, causing a flood that took out the Waiho bridge near Franz Joseph glacier.
Some experts have said big floods are becoming the new norm – not only because of climate change but also because of changes in the ways we use land.
3.The cost of floods is up
It all adds up. The cost of flood and storm events has increased at least four-fold from the 1970s, taking into account inflation.
The New Zealand Insurance Council has said 2021 might have been one of the worst and most expensive years when it comes to flood claims on record. The May Canterbury flooding cost around $44 million, the September Auckland floods around $57m and the July West Coast floods a staggering $85m.
4.Flood risk is actually super-specific
Flood risk is usually calculated across a town, city or region. Different district or regional councils offer flood maps that help people figure out how at risk they are, depending on where they live.
But as flood modelling gets better, insurers have tools that give people a sense of flood risk for an individual address. These newer models take into account factors like how close a house is to a river, how elevated the land is, where on the land the building sits, what the house is made out of, any flood walls in the city or how water flows in rivers nearby.
That means houses right next door to each other can actually have very different flood risk ratings.
5.Predicting flood risk takes tonnes of data
To get that level of precision, these models need a lot of data. Tower insurance invested in modelling, developed by analytics company Risk Management Solutions, that uses 5 million data points to simulate more than 350,000 flooding events over some 50,000 years. That information is then backed up by comparing it to 60 years' worth of insurance claims.
While we may not ever get weather predictions down to an exact, precise science, the result of all of that work is a model which can more effectively than ever predict a property's risk – and help you to prepare for what could happen.