by Hurricane Helene only lasted a few days in September 2024, but changed the landscape of the southeastern USA in a profound way that affect the dangers that the residents are far into the future.
Sludge conductors bury streets and converted river channels. Used trees left the floor on hills that were exposed to the elements. Sediments that washed into rivers changed the way water flows through the landscape and some areas more susceptible to floods and erosions.
Helene was a strong memory that natural hazards do not disappear when the sky is clear – they develop.
These transformations are part of what scientists call cascading dangers. They appear when a natural event changes the landscape in a way that leads to future dangers. A landslide triggered by a storm could clog a river, which leads to floods located months or years later. A forest fire can change the soil and vegetation and set the stage for rubble flows with the next rainstorm.
I study these disasters as a geomorphologist. In a new paper in the magazine Science, I and a team of scientists from 18 universities and the US Geological Survey are explaining why hazard models – to help communities in preparation for disasters – are not only dependent on the past. Instead, they have to be nimble enough to predict how dangers develop in real time.
The science behind the cascade dangers
Cascade dangers are not accidental. They arise from physical processes that continuously act about the landscape – sediment movement, weathering, erosion. Together, the atmosphere, biosphere and the earth constantly deform the conditions that cause natural disasters.
For example, earthquake fracture and shaking loose ground. Even if landslide does not occur during the quake itself, the ground can be weakened so that it is available on the failure during later rainstorms.
This was exactly what happened after the 2008 earthquake in the province of Sichuan in China, which led to an increase in ruins long after the initial seismic event.
The surface of the earth retains a “memory” of these events. In an earthquake, a running fire or a strong storm, the sediment moves over the years or even decades and converts the landscape as possible.
The Assam earthquake from 1950 in India is a striking example: it triggered thousands of landslides. The sediment of this landslide gradually moved through the river system and finally led to floods and changing river channels in Bangladesh about 20 years later.
An intensifying threat in a changing world
These risks face challenges for everything, from emergency planning to house insurance. After repeated forest fire mudlide combinations in California, some insurers cited completely from the state and cited the risks and increasing costs under the reasons.
Cascade dangers are not new, but their effects are increasing.
Climate change increases the frequency and severity of forest fires, storms and extreme rainfall. At the same time, urban development continues to expand into a steep, endangered terrain and exposes more people and infrastructures for the development of risks.
The increasing risk of interconnected climate disasters such as this consists of overwhelming systems for isolated events.
However, climate change is only part of the equation. Earth processes as earthquakes and volcanic eruptions, also cascade dangers, often with long-lasting effects.
Mount St. Helens is a strong example: More than four decades after its outbreak in 1980, the US Army Corps of Engineers continues to manage ashes and sediments from the outbreak to prevent river channels from filling in a way that could increase the flood risk in electricity -fitting communities.
Remember the risk and build up resistance
Traditionally, insurance companies and disaster managers have appreciated the risk of hazard by examining past events.
But if the landscape has changed, the past may no longer be a reliable guide for the future. To remedy this, computer models are needed on the basis of the physics of the work of these events to maintain the prediction of danger development in real time, similar to the weather models with new atmospheric data.
A landslide in March 2024 on the Oregon coast extinguished trees on the way. Brian Yaniten, June 2025
A drone image of the same landslide in March 2024 on the coast of Oregon shows where he temporarily thawed the river below. Brian Yaniten, June 2025
Thanks to the progress in straw observation technology such as satellite images, drones and lidar that resembles radar but uses light, scientists can now pursue how hills, rivers and vegetation change after disasters. These observations can insert themselves into geomorphic models that simulate how loosening sediment moves and where dangers probably appear next.
The researchers already have the weather forecasts with the processes after the wild fire. Other models simulate how to travel sediment impulses through river networks.
Cascadian dangers show that the earth’s surface is not a passive background, but an active, developed system. Each event redesigns the stage for the next.
Understanding these connections is crucial for the establishment of resistance so that the communities can withstand future storms, earthquakes and the problems through rubble currents. Better forecasts can inform building regulations, lead the design of the infrastructure and improve the prices and administration of the risk. You can help communities to anticipate long -term threats and adapt to the next disaster attacks.
The most important thing is that you challenge everyone to think beyond the immediate consequences of a disaster – and to recognize the slow, quiet transformations that build up to the next.
This article will be released from the conversation, a non -profit, independent news organization that brings you facts and trustworthy analyzes to help you understand our complex world. It was written by: Brian J. Yanites, Indiana University
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Brian J. Yanites receives funds from the National Science Foundation.
