Officials have closed a few local trails in the vicinity of the Mendenhall Glacier today as a result of rising water levels on Mendenhall Lake due to a glacial outburst flood.
Wendy Zirngibl, public affairs specialist for the Tongass National Forest, said West Glacier Trail is closed as rangers are “anticipating some water breaching that trail.”
Nugget Falls Trail closed around 4:30 p.m.
“The water has been rising a little more slowly than we anticipated,” said Zirngibl about an hour before the decision was made to close the trail. “... If it starts to look like the waters are coming in a little faster and it could be hazardous to travel on there, then we will close the trail.”
“We have not yet closed the Mendenhall Lake Campground,” Zirngibl said.
“Certainly, the campground is one of the most vulnerable of our facilities,” said Ed Grossman, recreation program manager at the Ranger District. “Right now, we have closed off the most vulnerable sites (at the campground), but we have not closed the campground yet.”
Grossman said flooding is not expected to be as severe as last July’s event, meaning the Mendenhall Lake Campground could potentially remain open.
Tom Mattice, Juneau’s emergency programs manager, said the Mendenhall Glacier’s Suicide Basin does not appear to be holding as much water as it was last year, but cautioned that the situation could change rapidly.
“The rate of discharge could totally change, and the amount of water that’s in that basin could totally change,” Mattice said. “We’re making some educated guesses, but they’re still guesses.”
At this time, Mattice said, the city is not expecting the flooding will force any evacuations.
National Weather Service forecaster Rick Fritsch said flooding is expected to peak between 9 and 10 a.m. Friday.
Water levels for Mendenhall River are forecast to crest at 12.08 feet, while Mendenhall Lake will reach water levels of 9.54 feet, Fritsch said, based on estimates as of noon Thursday.
That would make this July’s flood significantly less pronounced than last July’s flood, when the river crested to 13.07 feet and the lake reached 10.92 feet, Fritsch added.
“One foot makes a difference between people on View Drive being fully inundated, and a little water in the yard … (and) up to a foot of water in some people’s garages,” Fritsch said.
At noon Thursday, the National Weather Service replaced its Flood Watch for the City and Borough of Juneau with a Flood Advisory. Fritsch said that reflected forecasters’ confidence that there would be flooding, but also their expectation that flooding will not be severe.
“Watch is a maybe,” Fritsch explained. “A Flood Advisory is what we call minor or nuisance flooding. … A moderate flood is when we would escalate, take that Flood Advisory and make that a Flood Warning.”
Fritsch said the situation remains “very unpredictable.” While Suicide Basin remains under surveillance, he said, it is difficult to ascertain exactly how much water is in the basin, how quickly it is draining and precisely where the water is going.
“Last year, there was a huge geyser of water emanating from the right side of the glacier,” Fritsch said. So far, he added, he has not seen that happening this time.