Rising waters on Juneau’s Mendenhall River, stemming from the release of a glacial ice dam on a nearby lake, were threatening homes in the state capital’s most populous residential district Thursday morning, but the waters have begun to recede.
"It appears that most of the water has been squished out of that lake basin and it appears that the inflow to the lake has slowed and it appears that the lake has started to drop so things could change but we assume all trends are heading the safe direction," said Tom Mattice, Juneau's emergency programs manager.
According to a flood warning issued by the National Weather Service in Juneau at 9:25 a.m., a lake above Mendenhall Glacier, which had been choked by ice, flooded the river, with water levels on Mendenhall Lake adjacent to the glacier and the river in moderate flood stage at 10.61 feet and 12.78 feet respectively.
The river reached its peak height Thursday at about 11 a.m., at 13 feet high. It wasn't a record, but came close.
Juneau NBC affiliate KATH-TV says the river’s flow contains 10,000 cubic feet of water per second, versus normal flow rates of about 2,400 cubic feet per second. The river's rise is estimated at a couple of inches per hour, although waters are expected to drain when the lake empties.
Parts of the Mendenhall Campground have been evacuated due to flooding, and access to the West Mendenhall Glacier Trail has been cut off with water filling paths outside Skater's Cabin. View Drive was expected to be cut off by the flooding and completely flooded Thursday afternoon.
The NWS flood warning has been extended to 10 p.m. Thursday. The weather service advises people watching the flood to stay clear of potentially unstable riverbanks, and warns against crossing floodwaters on foot or in vehicles since even a foot of rushing water can sweep away a car.
"If you encounter a flooded roadway, turn around -- don’t drown," forecasters wrote.
The city also warned people to be cautious if they planned on heading to the river to see the damage. It said the banks are damaged and weakened by the flooding.
Officials planned to visit the lake above the glacier by helicopter to assess the possibility of further flooding later Thursday.
Editor's note: This story has been edited to clarify that the source of the flood is a lake above Mendenhall Glacier, not Mendenhall Lake.