![]() ![]() Wobbly idea 2: ‘Density means more disaster!’ It’s cheaper to build, easier to maintain and, perhaps most valuably, it doesn’t have the same capacity constraint. In a new subdivision in a big rain event, says Healthy Waters’ head of planning Nicholas Vigar, they plan for perhaps 40-50 per cent of the water to go down the drains, while 50-60 per cent will spill along an overland flow path. But choosing the best solutions for each area is complex and, these days, it doesn’t always rely on expensive pipes underground. There are some flood-prone areas we probably shouldn’t build on and some sections of coastline we should retreat from too. The same thing happened with new developments in Drury, Northcote and elsewhere. On the night of January 27-28, water ran down the streets and the suburb’s Freeland Reserve flooded, and over the next three days the water seeped away into the ground. In Mt Roskill, where Kainga Ora and others are building 10,000 new homes, the drains have been upgraded and, more importantly, “overland flow paths” and flood catchments have been established. But in the newer developments, the news tends to be much better. ![]() Most of them have been there a long time and some of them flood quite frequently. Its boss Craig McIlroy told me yesterday the city has 100,000 homes “on a flood plain”. Managing stormwater in Auckland is the job of Healthy Waters, a division of the council. In Auckland itself, the suburb of Sandringham used to be a swamp – what we now call a wetland – before it was drained and turned into a suburb. In many cities in Asia, there are houses on stilts above the water. In the Netherlands, most people live below sea level, protected by dykes. The history of cities is a history of how to manage the risks posed by water. Almost every city in the world is built on a river or a coastline, or both, and therefore is on or near flood plains. Wobbly idea 1: ‘Don’t build on a flood plain!’ Sadly, misleading numbers aren’t the only wobbly ideas getting in the way. He’s right, but despite the new-found consensus that Something Has To Be Done Now, the ferocity of these storms has revealed that we do not know enough about where and how we can live safely. We look ahead, to what the world might be like in 2050, and to if, or when, the temperature warms by 2 degrees above pre-industrial times, or 3 degrees, or more. The whole debate about climate change has been compromised by numbers like this. Some meteorologists prefer the term “1 per cent chance”, which means the same as “1 in 100″, but carries the message that, however small, there is a real chance it can happen.īut that’s not good enough, partly because it’s obviously out of date and partly because it still carries the message that we shouldn’t worry too much. And we will surely experience this awful record-breaking again. It was the same for the people of Hawkes Bay and Tairāwhiti. No one thought it could be that bad, and yet it was. The rains that fell on Auckland over January 27-28 were 60 per cent greater than those expected in a “1-in-100-year” rainstorm. One of the many brutal lessons of Cyclone Gabrielle and the Auckland Anniversary Weekend storm is that if extreme weather can happen this year, it can happen again next year.Īnother lesson: If the storm was unprecedented this time, that can also happen again. “We will be dealing with them regularly.” “There is no point talking about 1-in-100-year events anymore,” Finance Minister Grant Robertson told the Auckland Business Chamber last week.
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