Whether you rent or own, knowing your property’s flood risk is a smart way to stay safe. But how can you find out before it’s too late?
Historically, much of Wairau Valley has been a swamp. It wasn’t until the 20th century that the area – a natural valley with the Wairau Stream running through it – started to attract development amid the North Shore’s rapid urbanisation. Much of the valley’s waterways and farmland were converted into roads and lined with concrete. By the 1970s, Wairau Valley had transformed into a fully fledged industrial hub.
Since then, the area has become more of a commercial district filled with big box stores and car dealerships. But for a brief moment in January 2023, a stormy deluge saw Wairau Valley seemingly revert to its swampy roots. Businesses throughout the area were inundated with knee-deep flood water, while entire roads and parking lots disappeared under an ocean of rainfall. Suddenly, Wairau Valley (meaning “enclosed waters in a net” in te reo Māori) was living a bit too closely up to its name.
Today’s planning rules are shaped by a much better understanding of flood risk. Many older parts of Auckland, including Wairau Valley, were developed before we had this insight. As a result, many Aucklanders now find themselves – often unknowingly – living and working in vulnerable locations. Thousands of renters and homeowners were caught completely off guard by the January 2023 flash floods. Across the region, more than 10,000 properties flooded and many were forced into emergency accommodation by the devastating storms.
While Aucklanders are more flood aware than ever before, many still don’t know how to assess their risk. One of the easiest ways to find out if your current or future home is at risk of flooding is to search for the property on Flood Viewer – a free online tool developed by Auckland Council that highlights the different kinds of flood hazards that exist across the region. Nick Vigar, head of network planning for Healthy Waters, says that although the information powering Flood Viewer has been publicly available for a while now, it was important Auckland Council present that data in a format that was accessible and easy to understand.
“Unless you’re quite technical or somehow involved in the construction industry, most people won’t know how to find or interpret this information,” Vigar says. “That’s why we developed the Flood Viewer to not only help everyday people access that information more readily, but also [to help them] go further and take practical steps to prepare for these floods as well.”
Many properties across Tāmaki Makaurau are exposed to one or multiple flooding hazards – the Flood Viewer map uses several layers to show these and help users understand which hazards are present at their address. In flood plains and flood prone areas (which can occur on both natural and artificial terrain) the damage caused by intense rainfall can be significant as water pools and becomes trapped, often in normally dry areas. Huge swathes of the city are also exposed to overland flow paths – temporary fast flowing streams which activate when stormwater networks reach capacity or don’t exist. And for properties close to the shore, coastal inundation (when land becomes covered by sea water during large storms) is another flooding hazard. This is predicted to become more frequent as sea levels continue to rise as a result of climate change.
“Around 14% of our land is a flood plain, with around 20% of buildings in the region exposed to some kind of flood risk,” says Nancy Baines, senior flood risk specialist at Auckland Council. “A lot of people think if you’re not near a stream, you’re going to be okay. But so much of the flooding we see here in Tāmaki Makarau is in those short, sharp, steep catchments where the water is running across the surface of the land. So just because you’re far from a stream doesn’t mean you’re not at risk.”
According to Vigar, there are various reasons why some parts of the city are more likely to flood than others. “West Auckland, for example, is always a high risk region, and that’s really driven by high rainfall in the Waitakeres,” he says. Meanwhile in other parts of Auckland, bigger and longer weather events are more common due to the size of the catchment – a relative anomaly in Auckland where “short, sharp, flashy floods” tend to dominate.
Different parts of Tāmaki Makaurau have different kinds of flood risks – shaped by rainfall, geology and historical development. For example, West Auckland sees more intense rainfall from the Waitākere Ranges, while volcanic suburbs like Sandringham and Mt Eden have underground lava flows that create natural dips in the terrain. Flood Viewer helps you spot these kinds of risks in your area so you can prepare accordingly.
“In suburbs like Sandringham, Mt Eden, and Epsom where it’s a volcanic area, we don’t have much of a stormwater network in place at all. So instead, the water goes to the rock (the ground underneath) which is lava flow that’s solidified and is now full of holes and pockets. So if you go and look over those suburbs on Flood Viewer, you’ll see there are a lot of flood hazard areas caused by lava having cooled with a depression.”
In Wairau Valley, a complex mix of natural and artificial barriers have made the area particularly vulnerable to flooding. Currently, Auckland Council is looking to make significant infrastructural changes to prevent a repeat of 2023, including the option to repurpose the nearby Takapuna Golf Course into a multi-use recreational flood storage wetland. The development is part of the broader Making Space for Water programme co-funded by local council and central government, and has already greenlit flood prevention initiatives in suburbs like Rānui and Māngere.
Unfortunately, for the majority of Auckland’s flood hazard areas, infrastructure won’t provide a sufficient long-term solution. “For 95% of people with flooding, there aren’t really any viable infrastructural solutions that won’t cost more than the property itself. Often, it’ll turn out that a project will cost $10-15 million to complete but will only benefit a couple homes. So for the majority, we can’t really do anything for them which is a pretty horrendous position to be in,” says Vigar.
“What we can do though is give advice through tools like the Flood Viewer on what they can do to prevent or mitigate the effects of flooding. Right now, it’s the most practical thing we can do to help.”
While the layers on Flood Viewer are based on computer models that use verified science on rainfall as well as established modelling methods, it’s important to note the maps shouldn’t be taken as a perfect predictor of future flooding. “The predictions and layers on Flood Viewer are based on a number of things like rainfall, the topography, and the hydrology of past events,” Baines explains. “The tool is modelled after a designed storm so we can be consistent across the region. But in real life, rain falls in all sorts of different ways – it could be a 24 hour long event across all of Auckland, or just a 30 minute one limited to a small part of the city. That’s why areas that might not have flooded in 2023 are still being identified as potential flood hazard areas on the map.”
Another thing to consider is that Flood Viewer doesn’t factor in things like the number of floors in your home or how raised up off the ground it is. “In some suburbs and even on some streets, it’s possible for two houses virtually right next to each other to have completely different experiences,” says Baines. “For example, one person could be quite deep underwater while their neighbour could be totally fine.”
For this reason, Vigar adds it’s important for those looking to purchase property to do another, more in-depth layer of assessment. “That’s where things like LIM reports and property files come in, which will have a lot more detailed information about the property. And for those wanting to build their own homes, we recommend they approach us directly because we have all sorts of extra information we can provide for people like developers and engineers.”
For renters, however, Flood Viewer is a great way to understand your property’s risk without having to dig too deep into the finer details. And depending on where you are and the type of hazards you face, there are a number of simple yet effective things you can do to protect yourself and your home.
“It’s really important to have a plan ahead of time,” says Baines. That includes having a grab bag and knowing where to go if your home is inundated with flood water. For those at less severe risk, it means knowing what to do to reduce the odds of flood damage, like keeping gutters and drains around the property clear. “It also means making sure things like plant boxes and bins aren’t blocking the flow of water or, worse, accidentally directing water towards your property.”
The events of January 2023 have often been described as a “one-in-100-year event”, meaning such an event has a 1% chance of occurring in any given year. And while that might seem like a relatively low probability, it’s worth noting that extreme weather events are forecast to become “increasingly frequent and severe” in the coming years.
“In the future, the effects of things like climate change could mean that a one-in-100-year event might soon become a one-in-50-year or even a one-in-20-year event,” says Vigar. He cites one part of Auckland where the risk of flooding has changed considerably: ”What we previously thought was an event that had a 1% chance of occurring in any given year has now happened every year for the past three years. So there’s nothing to say that now you can’t get several 100-year events in a very short space of time.”
One silver lining from these devastating events is that now more than ever, we’re aware of the dangers of flooding and are willing to take action to combat a very real threat. The floods of 2023 left behind a trail of devastation, but that doesn’t mean we can’t take steps to make sure it doesn’t happen again.
“I’ve talked to a lot of flood-affected people over the last couple of years and there’s definitely a trauma associated with feeling powerless,” says Vigar. “The sheer power of flood water can be pretty humbling and scary, so hopefully this information and practical advice we’re sharing can help empower our residents to be prepared.”
