Ed Clayton: Thoughts on Auckland flooding. Is there a Way Forward?

Forwards or backwards

A guest post from Ed Clayton who has written for the blog before coving Green Infrastructure especially around Storm Water.

I’m writing a few days after Tāmaki Makarau received more rain in one day than it usually does all
summer. The Fire Service reported that every single vehicle was mobilised in response to the
flooding. MetService has just issued another warning for rain over the next 24 hours and NIWA has
predicted more moisture-laden tropical air making its way to us for the next 5 days. It’s just started
raining again outside.

Flooding has been so widespread that it’s likely this will be the costliest natural disaster for
Auckland. Climate change has exacerbated the floods, as warmer air can hold more moisture. I’m
certain that insurance companies will be taking a long hard look at how extreme house prices will be
affecting claims, along with a new affection for Auckland Council overland flow paths.
The flooding was so bad because Auckland has built over far too many of the small streams in the
city. We’ve removed the ability of streams to cope with large volumes of water by building on
floodplains and removing the hydraulic connectivity that is crucial for managing flood flows. Hard,
impervious surfaces remove the ability for water to soak in, instead funnelling it straight into our
stormwater system. And this carries with it the detritus of our urban spaces, resulting in pollution
and closed beaches.

Rain Gardens slow down runoff and flooding!

Wairau Valley is a perfect example of this mistreatment, concrete-lined channels and pipes cannot
cope with extreme deluges and so roads flooded, houses were swamped, cars swept away and
tragically, people died. However, where newer developments have been designed around more
water-sensitive designs, flooding was minimal. A perfect example is how Hobsonville Point coped
with the rain.

What can be learnt from this storm? A lot, if we want to, but as evidenced by Alec Tang, we haven’t
learned much from the last one. It’s great that our new subdivisions get raingardens, swales and
biofiltration devices, but for the already-built parts of our city, more is needed.
This post then, is a call for a new perspective on what water means for Aotearoa. We’ve just learnt
the hard way that all infrastructure is water infrastructure, and this means we need to re-evaluate
how and what we build. I’m advocating for all infrastructure to be assessed through a water-lens;
how does this apartment building improve water quality in the local stream? How can we increase
transport links and community connectivity while removing flood risk?

I’ve had thoughts about this for a long time, and I’m subscribing to ideas of ecological net-gain. If we
build something, it must improve water quality. No more offsetting or mitigation of effects. What
this looks like in practice means that, over time, we gradually improve all of our infrastructure. This
could be designing light rail to have green tracking, purposefully built to infiltrate and treat adjacent
land use runoff. It could be creating ecological build zones that grant bonus development rights to
buildings that incorporate green roofs.
It most definitely needs to be catchment-oriented planning, so that as we increase our urban
housing density, we increase our urban green spaces. Think pocket parks designed as stormwater
detention, but that are social spaces when dry.

Stormwater pocket park, Philadelphia

Identifying where our overland flow paths are and buying properties to create linear wetland parks
designed to flood and store water. Utilising concepts such as the Sponge City. Daylighting our buried
creeks like Waihorotiu to create more spaces like Te Auaunga. Reducing and redesigning roads for
private vehicles so that as we reduce our impervious cover, we also change the function of roads,
encouraging them to become ecological links.

The ultimate goal of this should be to reintroduce quality green and blue spaces back into our
neighbourhoods. We need to change our perception of stormwater away from one of nuisance, to
one of resource. This is the 15-minute city, but reimagined as access to local swimming holes with
great water quality. Sources of mahinga kai. Wetlands, native bush and streams that are biodiversity
hotspots in our city. We know the mental wellbeing benefits of being close to nature, by placing
water outcomes first we can start to create a city that improves wellbeing, is climate resilient and

None of these changes will be easy, and I’m sure there will be many detractors (“Kiwi’s love their
cars”). Much investment will be needed too, but as we find out more about the cost of this event in
the coming weeks and months, can we afford not to?

One thought on “Ed Clayton: Thoughts on Auckland flooding. Is there a Way Forward?

  1. Hi Ben and Ed.. A good article.. but where do I start to reply on this article… Friday night was 3 hours of 70mm to 78 mm rain . 25mm or 1 inches equals 100 tons of water per acre in old measurements I believe. I stand to be corrected o this. So unprecedented. Your ideas are good, correct and sound. But do we design for 1 in 200 year flood events now ? Or 1 in 500 year events. If so who pays…ultimately the end user.

    Is this just a fact of life of living on a flood plain, close to a river or stream on an Isthmus with 1 in 50 year designed flooding storm water systems and 53 dormant volcanic cones on an island subject to earthquakes ?

    So do we do a storm water retrofit for the City?

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