The 2024 floods highlighted the vulnerability of the Hrubý Jeseník Mountains
Researchers from the University of Ostrava have confirmed that even medium-altitude mountain areas are exposed to significant natural hazards. Based on field research and data analysis conducted after the 2024 floods, they identified the main patterns of debris flows in the Hrubý Jeseník Mountains. At the same time, they highlight the need for more systematic prevention in mountain regions that have so far been largely overlooked.
During the September 2024 floods, Storm Boris triggered dozens of debris flows in the Hrubý Jeseník Mountains, transporting large amounts of rocks, soil and wood from the slopes into mountain streams. This shows that such hazardous events also affect medium-altitude mountain ranges, which have not been a primary focus of debris-flow research.
“The exceptional impact of Storm Boris on the landscape was caused by a combination of prolonged rainfall followed by very intense precipitation, reaching up to 20 millimetres per hour. The slopes gradually became saturated with water, and the final intensification of rainfall acted as the direct trigger for debris-flow initiation. Slope stability was also reduced by poorly designed drainage from forest roads, which concentrated water in sensitive locations,” says Associate Professor Radek Tichavský from the Department of Physical Geography and Geoecology on behalf of the research team.
Available data show that the debris flows in the Hrubý Jeseník Mountains in 2024 were not significantly larger than those recorded in the past.
“It was not only the rainfall itself that played a decisive role, but above all the shape and characteristics of the terrain. Approximately 80 percent of both old and newly formed debris flows occurred on very steep slopes that function as natural funnels — during heavy rainfall, water is rapidly concentrated into narrow pathways and has little opportunity to disperse. These are precisely the locations where slope instability is greatest,” Radek Tichavský explains.
Based on an analysis of extreme rainfall events between 1900 and 2024, researchers note that while such events occurred in relatively regular cycles during the first half of the 20th century, they have become increasingly irregular and difficult to predict in recent decades. In combination with terrain characteristics, the proximity of inhabited valleys and human interventions, this significantly increases the risk of slope instability. The experts therefore recommend regular monitoring of hazardous slopes, improving drainage in mountain areas, especially along forest roads, and taking these risks into account in the long-term planning of mountain-region development.
The research findings were published in the journal Natural Hazards.
Updated: 18. 03. 2026
