Martin Brook: why you wouldn't build on much of Auckland's land if you started from scratch knowing what we know today

Of Interest

If we were building Auckland from a blank canvas with the knowledge we have today there are lots of places where you wouldn't build, says Martin Brook, Associate Professor of Applied Geology at the University of Auckland.

Speaking in the Of Interest podcast, Brook says this year's spate of extreme weather events means we are talking more about the dangers of floods, slips and landslides, but there's a lot of work to do to better prepare ourselves for future such events.

"Generally if we were planning we'd avoid slopes and flood plains and obviously that includes a lot of Auckland. In fact GNS reports in 2009 stated that most of Auckland is at moderate or high risk of landslides...That encompasses a lot of the landscape of Auckland and it would mean that we wouldn't build in a lot of Auckland," says Brook.

"If you look at the Auckland Unitary Plan it doesn't encompass the geomorphology [the study of landforms and landform evolution], if you like, which is the land forms and the earth's surface processes that are currently shaping our landscape."

"I think we build too close to slopes. We love doing that, we cut trees down, we love building mansions on slopes so we have wonderful views. We have a history in New Zealand of building on unstable land, and part of that is the 1981 Local Government Amendment Act which absolved councils of civil liability if they permitted building on unstable land," Brook says.

He says landslides have killed more people in NZ over the last 150 years than earthquakes.

In parts of Auckland Brook says there's a lack of adequate building set-back distances, being the distance between a dwelling and slope or cliff, with set-backs from the bottom of slopes also very important.

Ideally, Brook says, a house on a 30-metre high North Shore cliff should be set-back about 100 metres from the cliff edge.

Brook suggests we have a general issue of politicians not liking to make difficult decisions, but is encouraged by Finance Minister Grant Robertson recently providing risk categories and definitions for properties affected by flooding and cyclones.

"People are talking more about hazards other than earthquakes and volcanic eruptions. Storms do cause floods and landslides and we seem to get them rather often unfortunately. So people are talking about this which I think is great. So let's hope some good does come out of it," says Brook.

In the podcast Brook also talks about managed retreat, places becoming uninsurable, the idea for a national geotechnical control office perhaps within the Earthquake Commission, warning systems and monitoring of moisture levels in slopes, and why he'd prefer "a more holistic storm based approach" than Auckland Council's Making Space for Water initiative.
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