Fire investigators say an electrical short circuit caused the scrub fire which destroyed 54 homes and buildings in Lake Ōhau village in October last year.
This morning, Fire and Emergency New Zealand (FENZ) released the Lake Ōhau Wildfire Investigation Report and Lake Ōhau Operational Review, detailing how the fire happened and how effective the FENZ response was.
Just after 3am on 4 October 2020, Twizel and Omarama Volunteer Fire Brigades were the first crews on the scene of the blaze.
At the peak of the fire, there were 11 helicopters and more than 100 people deployed to support the response.
FENZ Te Kei Region manager Mike Grant said specialist fire investigators determined the cause of the fire was accidental.
It was caused by an electrical short circuit on a power pole several kilometres upwind of the village, which then ignited dry vegetation below the powerline.
"Vegetation, terrain, high temperatures and, in particular, severe winds contributed to the rapid spread of this fire towards the Lake Ōhau village and surrounding countryside," Grant said.
The investigation report noted the wind was some of the most intense experienced at Lake Ōhau, with the weather station at Pukaki Downs recording a wind gust of 127km/h at 3.30am at the time of the fire.
Strong winds continued for many days, making fire management difficult.
"[On] 6 October strong wind gusts of 163.5km/h at 04.29 am and 167.2 km/h at 05.44am were also recorded."
The report describes the fire as "one of New Zealand's most significant wildfires in recent history".
More than 5000 hectares of farmland, private property and Department of Conservation land was burnt, with the fire's perimeter being 54 kilometres at its height.
Grant said no lives were lost thanks to the quick actions of residents of the Lake Ōhau Alpine Village who enacted the community's wildfire plan.
"Recognising the wildfire risk, we have been working with the Lake Ōhau community for more than 20 years to develop a wildfire plan - and providing wildfire equipment and training," he said.
Grant also commended the work of the fire crews.
"The review praised the fire crews and residents for their fast actions in the face of fire conditions rarely seen in New Zealand. I commend their bravery. Their actions undoubtedly saved lives and several properties that would otherwise have been destroyed," he said.
The FENZ investigation has been carried out since the day of the fire, with fire personnel having regular contact with the Lake Ōhau and local farming communities over the past year.
Insurance costs for the fire have reached more than $35 million.