South Dunedin as we know it may be about to change.
City and regional councillors will have to make tough decisions on how to protect south Dunedin and its 10,000 residents from future flooding.
The decision-makers are being guided by scientists who have painted the most accurate geological picture they've ever had.
Wedged between Otago Harbour and the St Clair, St Kilda coasts is south Dunedin.
It's flat and built on reclaimed wetland. Drillcores, some as deep as 60 metres below the surface, reveal just what the foundation is made of.
"We've got some beach sand and then we're going down into some muds," said GNS engineering geologist Phil Glassey.
"Twenty-six-and-a-half metres and we've got some gravel. There's a lot of these muds beneath south Dunedin."
Funding from the regional council has allowed dozens of samples to be pulled from different drill sites over the past three years.
"It's swampy and it's also a little bit wet which has some health implications for houses."
South Dunedin sits largely right on sea level. A LIDAR scan, the first in more than a decade, paints the landscape in the most accurate picture. The area in green sits less than a metre above the sea. Forecast sea rises of 30cm put the area at even more risk.
"We expect that the sea will come up and push against the groundwater, we expect the rain will come down more and lift the groundwater," said Simon Cox, GNS principal scientist.
For the first time, pressure transducers scattered around south Dunedin give us an ultrasound-like look of how groundwater behaves.
One model shows the month of August 2019 after persistent heavy rain with red and orange pulses indicating above-average groundwater elevation pushing the underground water up and down.
For the more than 10,000 people who call south Dunedin home, the problem is the groundwater level sits just centimetres below the streets they live on.
Nearly 30 bores spread across the plain give the most accurate piezometer measurements.
Above the gutter sits entire neighbourhoods, businesses, schools and key roads - including the only land access to the peninsula.
"Shallow groundwater causes all sorts of problems. As it rises and comes into the foundations it can damage buildings, it can cause dampness in houses," said Cox.
South Dunedin is no stranger to floods. Homes were washed out in 2015 when infrastructure failed to cope with the deluge
"It may be that we have to eventually retreat from this land but in the meantime there's an awful lot of living to do," said Cox.
The fate of south Dunedin could be decided by the end of the month. An area with a long history and an uncertain future.
