An avalanche evacuation advisory remains in effect for one neighborhood that sits beneath Mount Juneau in Alaska’s capital city. And now, for the first time, the city is using a radar detection system to track avalanches that rumble down the mountain, thanks to state money freed up by the city and tribe’s disaster declaration last week.
Severin Staehly works for an avalanche technology start-up called Gravimon in Zurich, Switzerland. On Sunday, he installed the Doppler radar system at the Alaska Electric Light & Power substation on Douglas Island. It’s called an Avymonster, and it points at Mount Juneau continuously to scan for avalanches.
“We can really see where it happens and where it starts, where it ends, measure the speed and give all this information to the forecasters,” he said in an interview at City Hall.
Staehly said the Avymonster is popular in other places with high avalanche risk like Norway, Canada and the European Alps. He said he installed one in Alaska last week near Portage Lake, south of Anchorage.
John Bressette, the city’s avalanche advisor, said it works just like boat radar, so it can scan through the night and in poor weather. Now, the team won’t have to wait for clear weather to see whether avalanches occurred. The radar system notifies staff instantaneously.
“It allows us to detect avalanches when we can’t visually see them, which in Juneau is often with the darkness and with the weather,” he said.
Using drone flights and binoculars when the clouds rose a bit on Sunday, Bressette said he was able to see where avalanches released some snow down the Behrends path to the end of Judy Lane. But he said the avalanche didn’t start from high up the mountain.
“There’s a lot of undisturbed snow at the top of the Behrends pass still that hasn’t been affected yet,” he said. “We feel that there’s still potential for — if that were to go — to potentially reach homes.”
That’s where the city is still advising residents to keep clear. An evacuation advisory was issued Friday for residents living in avalanche hazard zones for all slide paths in downtown Juneau, and for part of Thane Road south of downtown. The advisory was lifted Sunday for everywhere but Behrends.
North of downtown, Bressette said he confirmed a loud avalanche reported on Thunder Mountain this morning around 9:00 a.m., but that it didn’t threaten homes.
Bressette said his next step is to work with the Alaska Department of Transportation and Public Facilities to fly a helicopter-mounted LIDAR sensor over the mountain to measure the snow. He also wants to dig snow pits to look at layers in the snowpack. He said that will help forecasters better estimate the risk to those who live in the Behrends path.
Ryan O’Shaughnessy, the city’s emergency programs manager, estimates the radar system and installation costs about $200,000 or less. Since Gov. Mike Dunleavy approved the city and tribe’s disaster declaration, he said the state is likely to pay for it.
“We’re very confident that this will be part of our public assistance reimbursement,” he said.
At the top of the White avalanche path on Mount Juneau, weather sensors track air temperature and snow depth. But avalanche experts say adding other sensors that measure wind, solar radiation and snowpack temperatures could also help refine avalanche risk assessments for downtown Juneau neighborhoods.