Glenorchy residents have received a raft of reports on the hazards from natural disasters and possible interventions. File photo. Photo: RNZ / Tess Brunton
Otago communities are getting closer to deciding how they want to adapt to hazards like flooding, earthquakes and liquefaction.
Glenorchy and Kinloch residents met with the Otago Regional Council to discuss the final two technical reports at a meeting on Tuesday night.
It has been two years since residents at the head of Lake Whakatipu were told about the extent of the risks they face from natural disasters.
Since then, there has been a raft of reports investigating the hazards and possible interventions, all working towards an adaptation strategy.
The two latest studies are some of the final pieces in the puzzle - one analysed the risks to life and property and the other about stopping flooding and erosion.
Otago Regional Council natural hazards manager Jean-Luc Payan said there were some promising results to share with the community.
"For the risk for life, the results were quite reassuring because they were indicating that the risk for life is acceptable," Payan said.
The picture was not so good for people's property, with the study finding a significant risk of damage from flooding and earthquakes.
Marcus Gibson from Beca said widespread liquefaction was predicted in Glenorchy, posing a risk to water supply, power, roading and telecommunications.
"We do get that it's all significant risk based on that criteria and a lot of that is because you only need a small amount of land damage to actually sustain quite a large amount of damage to a building," he said.
Dr Jean-Luc Payan said some of the property risks were localised, particularly for flooding in Glenorchy, and they were figuring out solutions.
"However, this is really assessing the risk as if nothing is done and the aim of the natural hazard adaptation programme is considering what can be done to reduce the risk."
The other study investigated options to help mitigate the flooding and erosion risks from the Dart and Rees rivers.
Bill Veale from Damwatch Engineering said the most viable option they found to protect Glenorchy from the Lower Rees was to raise existing floodbanks.
The estimated cost was between $1.6 million and $2.3 million for the design, consent and build.
It was a different story for the upper Rees River as the existing floodbanks were outflanked and overtopped during large floods, he said.
"There's really no silver bullet. We didn't look at options to raise existing floodbanks. The length of those floodbanks makes them quite expensive to implement. But also the long term resilience is very difficult to maintain due to those river bank erosion processes."
Payan said they had a wealth of information that has been gathered over recent years to help current and future decision making.
"We also want to work with the community to understand what people value, what people enjoy doing and how they want to be ready for the future," Payan said.
"We know things are going to change but the response to that is really something that needs to come from the community."
A community drop in session to discuss the report findings is being held on Wednesday afternoon at Glenorchy Hall.
A draft strategy to help the area adapt to natural hazards is expected to be released later this year with the final adaptation strategy due mid next year.