Why Cruise Ships Are Ill-Equipped to Handle Sudden Tsunami Events
Landslides can cause sudden, powerful tsunamis—and no one really knows how to navigate them.
This article was originally published by Hakai Magazine.
In 2015, 76 million cubic meters of rock crashed from the rugged cliffs above a southeastern Alaska fjord and into the water below. The landslide sparked a nearly 200-meter-tall wave that roared down the narrow Taan Fiord and out into Icy Bay. No one witnessed the collapse, but a year later, the geologist Bretwood Higman was in the area taking detailed measurements of the tsunami’s effects. Looking up from his work, Higman saw a massive cruise ship crossing the fjord’s mouth. He was stunned.
“It’d never occurred to me that a cruise ship would go into Icy Bay,” Higman says. An image of tsunami-tossed ships trapped in the rocky passage filled his mind. “There are many ways in which that could work out really badly.” He couldn’t get the picture out of his head.
Landslide-generated tsunis are rare but potentially disastrous events. The warming climate contributes to glacier melt, rendering the steep slopes of southeastern Alaska’s fjords unstable. Previously supported by ice, several cliffs are now unsupported due to the rapid retreat of glaciers. Additional hazards are introduced by heavy rainfall and thawing permafrost. With an increase in tourism to Alaska’s rugged coastline, the concentrations of people in high-risk areas have also increased, heightening vulnerability to disasters. This issue is not unique to Alaska and is replicated in coastal areas worldwide including places like Greenland, Chile, Norway, and New Zealand.
Unlike tsunamis caused by distant offshore earthquakes, which provide a lead time before impacting coastal areas, tsunamis caused by coastal landslides occur abruptly and can generate much higher waves. This immediate threat poses significant danger to individuals in boats.
Read: The lifesaving potential of underwater earthquake monitors
The mounting threat profoundly concerns Amanda Bauer, who has been conducting day cruises around Alaska’s Prince William Sound for 17 years. Her route includes navigating through the tight channels of the Barry Arm fjord, beneath a massive, unstable 500-million-cubic-meter mass teetering above the withdrawing Barry Glacier. Bauer often contemplates the dangers while on these waters, particularly when surrounded by ice and unable to accelerate beyond two knots, unlike in open waters where rapid escape is feasible.
Exploring the best practices for maritime response to extreme tsunami threats, Higman delved into scientific research with a focus on tsunamis triggered by coastal landslides. Despite his efforts, Higman found little to rely on, encountering only a few case studies and historical accounts such as a disastrous wave in 1958 in Lituya Bay, Alaska, which was almost as tall as Toronto’s CN Tower and resulted in the capsize of two boats and the loss of five lives. Current scientific modeling of these tsunami events and their impact on ships is in its early stages, leaving significant gaps in effective guidance for ship captains.
Higman also reviewed guidance from the National Tsunami Hazard Mitigation Program in the United States, but found it insufficient. The existing protocols suggest that vessels at dock should evacuate to higher ground, those in deep waters should move to deeper waters, and those near the coast should either beach the vessel and escape on foot or head to deeper waters. These recommendations, designed to be universally applicable from small fishing boats to large passenger ships, do not account for the unique challenges posed by different vessel types and scenarios.
One critical challenge Higman identified is the unpredictable nature of landslide-generated tsunamis, which can occur suddenly, often without enough time for detection and adequate warning. This makes it impractical for captains to consider beaching their vessel as a viable emergency plan, especially given the rough terrain along parts of the Alaskan coast and the uncertainty around the timing and reach of the tsunami.
Furthermore, Higman suggests that current guidelines could be enhanced by better explaining the fundamental differences between tsunami waves and the wind-driven waves that mariners are accustomed to. Tsunami waves accelerate in deep water and increase in height in shallow waters. Given the varied depths of Alaska’s fjords, this can deceive captains into underestimating the speed of an approaching tsunami, potentially leading to dangerous situations where the wave overtakes the vessel unexpectedly.
Tsunamis confined to fjords also tend to slosh around like water in a bathtub, creating unpredictable currents in excess of 100 kilometers per hour. Those three bullet points of guidance don’t get into these nuances of tsunamis’ interactions with Alaska’s complex shoreline, Higman says. The current guidelines may also underestimate the expertise of vessel operators, he says, who are used to making quick decisions in hazardous conditions.
Elena Suleimani, a tsunami modeler for the Alaska Earthquake Center and co-author of the existing guidelines, admits that they’re imperfect. Although she’s created harbor-specific maps outlining where the water is deep enough for a ship to safely ride out a tsunami, Suleimani doesn’t feel comfortable giving advice to vessel operators: “I have no idea how to operate boats,” she says.
So, on a mission to give captains the best advice possible, Higman is running a workshop with the Prince William Sound Regional Citizens’ Advisory Council (RCAC) in Valdez, Alaska, this month. The event will bring together tsunami scientists and vessel operators to compile their knowledge and, hopefully, work out some more practicable recommendations.
At this point, Higman can’t say exactly what the proper guidance should be. But although the workshop will focus on improving advice for the captains of small craft, Chad Hults, a geologist with the National Park Service, says operators of larger vessels, such as cruise ships, need to consider the threat of landslide-generated tsunis as well. Hults says the NPS is keen to begin talks with the cruise lines that frequent Glacier Bay, where a dozen slabs of land seem ready to slide at any moment.
During tourism season, Hults says, “we have 260 cruise ships—two cruise ships a day—going into Glacier Bay. There’s no other place in the park system where we have 4,000 people on a boat and a pretty obvious hazard that could cause some harm.”
Similarly, says Alan Sorum, the maritime-operations project manager for the Prince William Sound RCAC, there are no official tsunami hazard guidelines for the oil tankers visiting Valdez, Alaska—the endpoint of the Trans-Alaska Pipeline. “If you capsize a big vessel like that,” Sorum says, “it would be a big problem cleaning that up.”
So far, Alaska’s mariners have managed to avoid the worst. A tsunami hasn’t caused an oil spill or killed anyone aboard a boat in Alaska in 60 years. “With all my effort on this, there’s this voice in the to the back of my head that’s like, ‘Maybe it’s not a big deal; maybe I’m wasting my time,’” Higman says.
But then he thinks about Barry Arm, Lituya Bay, and the cruise ship he saw sailing past the mouth of Taan Fiord. He tallies the dozens of unstable slopes known to be lurking across Alaska, all waiting to collapse into bays and fjords. “And,” he says, “I do think that, at some point, the situation is going to explode.”
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