EQC funds eyes in the sky on Auckland landslides

27 February 2018

EQC funds eyes in the sky on Auckland landslides

It can really rain in Auckland and that rain can set off landslides. Not always the big landslides with rocks and chaos that make it to YouTube, says University of Auckland researcher Dr Martin Brook, but “small and slow moving” landslides that will take away someone’s backyard, affecting their life at home, and the home’s value.

Dr Brook and his team have just been provided with funding through EQC’s Biennial Grants programme to use fast and economical new technology to see how land is moving on 10 slopes in different parts of Auckland.

“We know we have areas like Avondale, parts of the North Shore, East Coast Bays, Orakei Basin and others places where the water builds up under the soil.

“On these slopes, the water soaks into the soil, but it can hit a barrier layer (like clay or hard rock) and so can’t soak further down. As it rains, the water pressure within the spaces between individual soil particles keeps building up. Eventually, the soaked soil will start to move down the slope, creating a landslide and gradually taking anything built on it with it.

“What we’ll be doing is using drones to take very detailed photos of the slopes and putting the data through software to produce 3D models of the ground. We can then compare these to the laser (Lidar) generated data that has been done in the past to see how much the ground has shifted.

“Because our system of getting the data is so much cheaper, we can also take readings four times a year and get a good sense of how fast the ground on a slope is moving. And we can also cross check this by taking regular photos that compare the ground to a fixed point like a fence or lamp post.

“All of this gives us a really good idea of how a slope is moving, and this is important data for people wanting to use the land. It gives the Council, developers and homeowners the opportunity to take action to reduce the risk of a landslide on slopes with at-risk land types,” says Dr Brook.

Results from the survey will be used by Auckland Council’s Geotechnical team among others. “We have Auckland Council geotechnical scientists on the research team. They’ll be looking at the data itself, and also at the techniques we’ve used to get the data to see if it’s something they might want to use more widely around the city,” he says.

Dr Hugh Cowan, EQC General Manager Resilience, says research on landslides is very important for New Zealand.

“Most years, EQC gets more claims for landslide damage than any other natural hazard. Dr Brook and his team will not only get valuable data for Auckland Council on the specific research sites, but they are developing a cost-effective way for any council to map the stability of slopes. This is particularly important where land may be opened up for residential development in future,” says Dr Cowan.

EQC invests more than $16 million every year in research to reduce the impact of natural disaster on people and property.

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