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‘No similarities between what happened in Nepal and the flooding from Suicide Basin,’ local scientist says
- Mark Sabbatini
- 7 hours ago
- 4 min read
Glacial collapse that killed hundreds in Nepal prompts widespread look at other areas threatened by glacial-related flood hazards
By Mark Sabbatini
Juneau Independent
The catastrophic glacial collapse in Nepal that created a massive wall of floodwater and killed hundreds of people this week is not a situation that could happen with Suicide Basin and the Mendenhall River, according to a local expert.
Mendenhall Glacier’s ice dam has a different structure that cannot collapse in the same way as the glacier in Nepal, according to University of Alaska Southeast hydrologist Eran Hood. Also, Suicide Basin is a closely watched site where a flood can be predicted and water releases comparatively slowly. In contrast, the Nepal flood was a sudden event with an immediate, enormous outflow.
"We can watch (Suicide Basin) fill on the camera when it starts to drain," he said in an interview Friday. "We know it's starting to drain. We measure it with drones. We know how much water is stored there. That's really on the end of the spectrum of a glacier outburst flood that's eminently modelable."
"On the other end of the spectrum is what's going on in Nepal where you have these catastrophic releases of some combination of glacier ice collapse, and mountainside and landslide collapse that's liquefying. That's very difficult to predict where it's going to occur or when it's going to occur."
Hood provided a more succinct summary after questions posed by members of the citizen group Juneau Flood Solution Advocates, which shared his observations in a social media post Thursday evening.
"The short answer is that there are no similarities between what happened in Nepal and the flooding from Suicide Basin," Hood told the group.
A more comparable situation in Southeast Alaska is a megatsunami in Tracy Arm last year in which a receding glacier helped trigger a landslide, Hood told the Juneau Independent on Friday.
"There's a much closer comparison to what happened there to Nepal, because essentially…it was some combination of glacier collapse and bedrock failure and landslide," he said.
The Nepal flood occurred when a massive ice section about 2,000 feet wide snapped off a Himalayan glacier and fell thousands of feet to the valley floor in Langtang National Park, located about 35 miles north of the capital city of Kathmandu. News reports stated a river downstream rose 30 feet in 30 minutes, and peak floodwaters may have reached 160 feet high with the water moving up to 44 miles per hour.
In comparison, the level of the Mendenhall River rose from a pre-flood level of just over four feet to a peak of 14.7 feet over 45 hours during a glacial flood this month.
"The flood that we have has to drain under the Mendenhall Glacier and so there are physical constraints to the rate at which the water can drain under the glacier," Hood said. "A lot of people talk about Mendenhall like it's a dam burst, but it's not. It's a controlled release, which ends up as a flood because there's 16 billion gallons of water. But it's not like the Mendenhall Glacier is breaking apart and the water's flowing out."
The tsunami in Tracy Arm triggered an initial wave of 328 feet that rose 1,580 feet against a slope on the opposite side of the fjord, making it the second-highest ever recorded. It was triggered when a rock wall destabilized by glacier melt collapsed, with the water flow boosted by rainfall. While cruise ships travel in the fjord, there are no nearby towns and no injuries were reported.
But the question about whether Juneau and other communities near glaciers are facing risks on a Nepal-like scale is now being asked worldwide.
Newsweek, in an article Thursday headlined "Map Shows US Glaciers at Risk After Nepal Disaster," focuses first on Juneau because of its unusual combination of a recurring threat to a populated community.
"While many glacier-related floods occur in remote mountain regions, Suicide Basin has produced annual releases since 2011 and repeatedly affected homes, roads and infrastructure in the Mendenhall Valley," the article notes. "As a result, researchers and emergency managers often regard Juneau as one of the continent's clearest examples of an active urban glacier-flood threat."
National Geographic and Fox News referenced the Tracy Arm tsunami in reports about global locations exposed to large-scale glacial flooding risks.
"It was only because the megatsunami happened in the early hours that the fjord was mercifully empty at the time," National Geographic reported in its article Thursday, headlined "Nepal’s Glaciers Will Flood Again. Can Scientists Predict the Next One?" The magazine also examined other large-scale and increasingly unpredictable glacial flooding threats worldwide.
"Although this specific catastrophe (in Nepal) was unanticipated, this type of hazard — the rapid, violent collapse of a glacier — is becoming par for the course in a rapidly warming world," the magazine’s report states. "Anthropogenic climate change is thawing glaciers at an unparalleled pace. Melt them enough, and those dangling precariously atop mountains will smash into whatever resides below."
The Fox News report provides a similar summary, noting, "While early warning systems can help communities prepare, experts say the remote locations can make detecting and responding to sudden collapses challenging."
There has also been misinformation on social media, including a video of a helicopter flying above Suicide Basin during a water release that was depicted as the Nepal flood (the inaccuracy is noted in a Meta.ai fact check attached to the post).
• Contact Mark Sabbatini at editor@juneauindependent.com or (907) 957-2306.
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