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When an extreme weather event occurs, the probability or risk of other events can often increase, leading to what researchers call "cascading" hazards.

For example, the danger of landslides or debris flows following wildfires in California, recent flash floods in West Virginia or when historic flooding occurred in North Carolina as Hurricane Helene made its way inland. Such occurrences leave lasting imprints on the landscape that can prime Earth's surface for subsequent events.

As part of a collaboration by dozens of researchers across the country, a new paper in Science, titled "Cascading land surface hazards as a nexus in the Earth's system," outlines a framework to better predict, understand and forecast the cascade (or chain reaction) of these hazards across the landscape.

"There is a scientific need for improving our understanding of these cascading hazards," said Brian Yanites, lead author and associate professor of earth and atmospheric sciences in the College of Arts and Sciences at Indiana University. "If we want to better prepare for events like hurricanes, we need to also understand a hurricane's connection to other hazards.

"How does a hurricane or an earthquake impact the landscape and change the risk for future landslides or floods? How do landslides change river systems' flooding potential downstream because they suddenly have extra sediment? And how does Earth's biosphere, including the microbes converting rock to movable sediment and tree roots holding soil in place, impact these cascades?"

The paper comes from researchers at the Center for Land Surface Hazards Catalyst (CLaSH). Led by Marin Clark of the University of Michigan, the Center Catalyst brought together experts from across the country to analyze existing research gaps to better understand connections between Earth systems and processes that change as a consequence of Earth's shifting surface.

"It's really been work that's come forward in just the last 10 years, following some major events—fires, earthquakes, hurricanes," said Clark, co-author and professor of earth and environmental science at the University of Michigan. "These have given rise to data sets and the thinking about how we can piece together these processes to predict future hazard conditions."

In real time

"It's a vivid memory for me—the Tuesday before Hurricane Helene," said Yanites. "I emailed the research team that's been working on this new National Center, and I said, 'This is going to be bad for southern Appalachia.' We started monitoring it that night, knowing that there were going to be landslides and flooding. 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 consequences for downstream processes and impacts?'"

Researchers say this new framework could also help with disaster response to build societal resilience after natural hazards.

"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," said Clark. "That underpins disaster response and enables training of 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."

Yanites added that this could also help the insurance industry better understand potential hazards.

"In California, we're seeing a number of major insurance companies that aren't offering new homeowner insurance in areas because of cascading hazards, such as a debris flow that happens five years after a wildfire," said Yanites. "They don't understand how to price cascading hazards into their models."

Researchers hope to use this future framework to provide a path toward developing actionable plans for communities to prepare for cascading hazards. They also hope to create a "cascading hazards index" to give local communities context for potential cascading events.