Study: Cascading land surface hazards as a nexus in the Earth system (DOI: 10.1126/science.adp9559)
U-M is helping lead a collaboration to better forecast the chain reactions of downstream damages caused by wildfires, hurricanes, earthquakes and more
When the flames of January's Southern California wildfires were contained, residents knew the dangers weren't over.
The fires had primed some of L.A.'s hillsides for mudslides when February's rains came. Those mudslides, in turn, can reshape the landscape in ways that create new hazards, for instance, by blocking drainage paths and increasing future flood risks.
"These hazards don't exist as single, isolated phenomena," said Marin Clark, a University of Michigan professor of earth and environmental sciences. "That first event sets off a chain reaction of hazardous events that are related to one another."
Such chains exist across the spectrum of disasters, including California's fires, dams failing in Michigan and hurricanes penetrating into Appalachia. But how nature and our built environments have set up the dominoes usually only becomes obvious once they start falling.
That's why Clark and a cohort of colleagues from across the U.S. are working to build up our ability to understand and predict these linked, or cascading, hazards, as documented in a new report in the journal Science.
"It's really been work that's come forward in just the last 10 years, following some major events-fires, earthquakes, hurricanes," Clark said. "These events have given rise to data sets and the thinking about how we can piece together these processes to predict future hazard conditions."
Clark is also the lead investigator of the Center for Land Surface Hazards Catalyst, or CLaSH, a project supported by the National Science Foundation to accelerate this work. CLaSH began as what's known as an NSF Center Catalyst, a sort of prototype center that could crystallize a group of experts to lead transformative research in areas of pressing scientific needs for the country.
Reducing the impacts of surface hazards is a national priority, as evidenced by the National Landslide Preparedness Act of 2021, for example, which was renewed in 2024. Compared to the major events that reshape landscapes, the connected hazards left in their wake are understudied, leaving us more vulnerable to their risks, Clark said. Scientists can thus help the country meet its goals in this space by closing that gap.
"The federal government and state agencies are charged with reducing losses related to disasters, but we really lack an academic research community in the U.S. focused on primary basic research," Clark said. "That underpins disaster response and enables training a future workforce capable of meeting the urgent and growing need for resilience to natural hazards. This resilience is essential for both safety and economic growth."
That's why the CLaSH Catalyst was created and why its members, including Clark and lead author Brian Yanites of Indiana University, published the new Science report. And the group is laying the groundwork to develop the tools, techniques and workforce that can build resilience to the downstream impacts of disasters, saving lives and billions of dollars in damages.
A call to action
"It's a really vivid memory for me, the Tuesday before Hurricane Helene made landfall," said Yanites, IU assistant professor of earth and atmospheric sciences. "I emailed the research team that's been working on this new national center and said, 'This is going to be bad for southern Appalachia.'"
Yanites and his team had already been studying the area and knew the hurricane could trigger further events. But knowing what is possible is different from being able to predict what is likely to happen. That's what researchers are working toward, but the field simply isn't there yet.
"We started monitoring it Tuesday night, knowing that there was going to be lots of landslides and flooding," Yanites said. "But we don't really have the scientific tools to go and say, 'How many landslides? Where are they going to be? What are the sort of consequences for downstream processes and impacts?'"
Events like these can also have long tails, said Josh West, a professor of earth sciences and environmental studies at the University of Southern California and CLaSH co-investigator. The flooding and landslides caused by such an intense event push sediment and debris into river valleys, which clog the natural escape route for water from future rain. As a result, the flooding risk in these areas can remain elevated for years, if not decades.
Outside the research community, not many folks think about these linked hazards, West said. But a center like CLaSH can help raise awareness around these issues so residents and support agencies are more prepared.
"Helene is a really good example, but you have events like these around the world," West said. "There are these ramifications that last for years and years and years, and they knock on in ways that you wouldn't anticipate."
This is somewhat in contrast to California's wildfires and their subsequent hazards, which West also studies. The fires are frequent enough that residents know, almost intuitively, that the risk of mudslides will be heightened the following winter when the rains come.
But even here there is room for improvement and new knowledge that can be delivered by an initiative like CLaSH. Recent research has revealed that how soil in burnt areas repels or absorbs water isn't as cut and dried as once thought.
"On the one hand, you can say that's just a detail," West said. "On the other hand, it's really important to get such details right if we want to understand and forecast these chains of hazards in the future."
In its catalyst phase, CLaSH started bringing together experts from a range of backgrounds to add new perspectives to how researchers discover and analyze these details-and how they add up to form the long-lasting hazard cascade. By continuing to foster this forum, the CLaSH team aims to bridge the fundamental and applied research communities to bolster the nation's resilience to cascading hazards.
"We've already seen this in the catalyst phase, that the whole is greater than the sum of its parts," West said. "The research community hasn't really had anything like this before and there's a lot of excitement for it."
Impact at the community scale
Another thing that makes this research challenging is that the scales of different hazards and their downstream impacts don't fit neatly into one realm of research, said Dimitrios Zekkos, co-author of the Science study and CLaSH co-investigator. In his discipline of civil and environmental engineering, for example, people are very good at making individual structures safe against specific threats.
"We can safely design a building during an earthquake, but what about the broader community? What about the roads, energy, water and everything that goes with living? Will there be other cascade events such as fires and landslides?" said Zekkos, a professor at the University of California Berkeley. "Being safe in my own building isn't enough. The community resilience isn't there."
Bringing together a wide range of experts who study hazards and their interdependencies at different scales is a key way to address that challenge. To date, CLaSH has engaged with more than 600 researchers.
Technological advances have also been a huge asset for researchers working to address cascading hazards at the community scale. With the emergence of drones and other robotics, as well as improvements in remote sensing with satellites, researchers can observe more places in greater detail. They can more easily investigate areas immediately following a disaster, but the technology is also making it possible to understand what conditions existed beforehand.
"What we're seeing now with drones and satellites and related technologies was inconceivable even five years ago," Zekkos said.
The tools are generating massive amounts of new data, which in turn help experts build better computer models. These models can address entire regions to help people predict and prepare for cascading hazards.
Making the benefits of those tools, data and models more accessible to more communities across the U.S. is a long-term goal for CLaSH, but one that is already well underway. The work of Josh Roering, professor of earth sciences at the University of Oregon and co-investigator of CLaSH, provides an example of that.
His team studies, among other things, the debris flows that are a concern in very steep mountainous areas, such as Klukwan in southeastern Alaska, where his group does field work. Here, rocks and soil frequently fall down steep inclines into catchments, where they accumulate until freed by rain and meltwater. The resulting flows can be devastating.
"Debris flows are like floods, but rather than just water, they have boulders, trees and other materials that can make them really destructive," said Roering, who is also a co-author of the Science report.
The Alaska Native residents of Klukwan have been living with these flows for time immemorial. In fact, they've built their community on land constructed from the accumulation of these flows. But conditions are changing.
There's been the adoption of Western building and infrastructure practices that Klukwan now relies on. And atmospheric rivers are driving more intense rains, while rising temperatures are affecting the permafrost layers that bind the rocks where the debris flows are generated.
Roering and his team have been working with the Indigenous community in Klukwan to better prepare for the changing threat of the flows with monitoring tools and mitigation measures, like berm building.
"So we're doing a fair amount together already, but continuing to work with CLaSH would let us take the next steps and ramp everything up," he said. "It would take our work to the next level."
The CLaSH Catalyst has brought together a community of researchers to work collectively on these problems more effectively and efficiently than they could in isolation. Now, sustaining and building on that effort and collaboration could more quickly deliver actionable results to real-world communities.
"I think that's what makes our work unique and important," Clark said. "This isn't something that one researcher is going to be able to do. We really need the talents and perspectives of a broad range of scientists across the discipline."
