Lahars, or mudflows from the eruptions of glacier-covered volcanoes, are a threat that the communities of Skagit Valley in northwest Washington live with. These destructive mudflows can be triggered during volcanic eruptions when hot water and debris rush downslope from the volcano and mix with glacial water. A recent study from the Journal of Applied Volcanology by Corwin et al., identifies ways to improve hazard management and community preparedness in Washington’s Skagit Valley, home to Mount Baker, the second most glaciated volcano in the Cascade Range, and Glacier Peak, the second most explosive. The highly populated communities within Skagit Valley remain especially at risk for dangerous mudflows since both Mount Baker and Glacier Peak are considered active lahar hazard zones.
All five of Washington’s Cascade Range volcanoes are active. These volcanoes are especially dangerous because in addition to flowing molten lava and spewed ash that can destroy everything downhill, volcanoes with snow and ice at their peaks can create additional perils. Heat from the eruption can melt the snow or ice that has accumulated, create mud, and pour down narrow mountain valleys. This mixture of water and rock fragments that flows downslope of a volcano into a river valley has dangerous repercussions for communities like those in the Skagit Valley.
While lahars can be visually stunning when the volcanic material interacts with glaciers — see the remarkable images in GlacierHub’s recent article on these events in the Kamchatka Peninsula in Far East Russia — lahars can cause extensive damage to the built environment as boulders destroy structures and mud buries entire communities. Moving lahars appear as a roiling slurry of wet concrete and can grow in volume as they incorporate everything in their path — rocks, soil, vegetation, and even buildings and bridges.
Corwin et al. determined that a crucial disaster risk management strategy for lahar events is “whole community” training programs, which emphasize household preparedness and help disaster responders better perform their duties. Since lahars can cause widespread damage to the surrounding environment, it is important for community members to understand how to address the hazard before it occurs.
The focus of the research was on the ascription of responsibility on preparedness and the influence of professional participation in hazard management on household preparedness and risk perception. Disaster response professionals know the best household preparedness measures, yet they sometimes fail to implement these measures in their own households. The study found that this may be a result of professional disaster responders being out in the field during a disaster, instead of in their homes.
Even more surprising, response professionals failed to interpret local volcanic hazard maps more accurately than laypeople. There could be several reasons for this that need to be explored in a subsequent study, but as Kimberley Corwin, a geoscientist and the leading author of the study, explains, it could be because “people in both groups drew on outside information such as what they remembered or learned about the 1980 Mount St. Helens eruption.”
When asked by GlacierHub about her familiarity with lahars, Corwin described her closest experience with an active volcano in Chile’s March 2015 Villarrica volcano eruption. Corwin was in Pucón, Chile, for a volcanology course with Boise State University. The group of academics arrived two weeks after the main fire fountain event, which triggered a lahar. There was still active ash venting in the area.
“While we were there, the alert levels in the town were elevated and a 5-kilometer exclusion zone was set up around the vent,” Corwin explained. “It offered a great opportunity to observe the reactions of locals, tourists, and officials.”
Corwin’s further research found that preparedness measures are crucial in areas that are prone to natural disasters, as they can help professional responders and other community members protect themselves and their families.
A video of a 2003 lahar event in East Java, Indonesia, at the Semeru volcano (Source: adripicou/YouTube).
In the Skagit Valley, nearly all the community members correctly identified that lahars pose a risk to the region. However, when questioned about their confidence level on how to respond to a lahar, the participants demonstrated decreased self-assurance. They answered by saying that they have higher confidence when responding to floods, as these natural events occur more frequently than lahars.
Some recommendations for implementing “whole community” training programs involve increasing community participation in hazard management, identifying where community members can access hazard information, and providing instructions on how to interpret this information. Overall, these recommendations would increase household preparedness and allow professional responders to successfully complete their tasks without worrying about the safety of their families back home. In this way, community members would reclaim responsibility for their personal safety, and professional responders could feel more comfortable responding during a hazardous lahar event.