AvaForCE

Avalanche Mitigation and Forest Dynamics under Climate Change in the Mountains of Southeastern Europe and the Alps

Every winter, snow avalanches claim more than 100 lives across Europe’s mountains. They damage roads, buildings and ski infrastructure, and they reshape entire mountain forests. Climate change is altering how and when they happen. Warmer winters and shifting precipitation are changing the snowpack, bringing more wet-snow avalanches and new, less familiar avalanche situations.

AvaForCE is a joint research project by Switzerland, Bulgaria and Romania. It investigates the largest and most destructive avalanches: how often they happened in the past, what weather and climate conditions trigger them, how they interact with mountain forests, and how the risk may change in the future.

Why this project matters

Switzerland has one of the world’s best avalanche records, with documentation going back to the 19th century, detailed hazard maps and advanced simulation tools. In the mountains of Bulgaria and Romania, such information is still largely missing. Few long-term avalanche records exist there, and large-scale hazard maps are lacking for most regions.

Winter tourism is growing fast in places like Pirin, Rila, Bucegi and Făgăraș, and new ski areas, roads and huts are being built in avalanche terrain. Many avalanche paths show clear evidence of large past events, but skiers, hikers and even land managers often do not recognize them, because these events may happen only once every few decades.

AvaForCE brings Swiss expertise and Southeast European field knowledge together. Swiss methods and tools are tested and adapted in Southeast Europe, and the new data from Bulgaria and Romania improves models used everywhere.

What we want to find out

 The project has four main objectives:

1. Reconstruct the history of large avalanches in selected sites in Bulgaria and Romania, filling gaps where written records do not exist.

2. Identify the climate and weather patterns behind large-magnitude avalanches in Switzerland, Bulgaria and Romania, and check whether these drivers are the same across regions.

3. Detect changes over time. We want to see whether large avalanches have become more or less frequent as the climate and forest cover changed.

4. Simulate avalanches and map hazards. We will run numerical avalanche simulations, check them against real past events, and use them to produce local and large-scale hazard indication maps for Bulgaria and Romania.

How we study avalanches

Reading the history in tree rings. Trees remember avalanches. When an avalanche hits a tree, it can break, tilt, scar or bury it, and these injuries leave lasting marks in the annual growth rings: scars, sudden growth suppression, reaction wood and rows of resin ducts. By coring damaged trees and recording the exact location of each one, we can date past avalanches year by year and reconstruct how far they reached. This works even centuries back, in places where nobody kept records. This method is called dendrogeomorphology.

Old maps, aerial photos and satellite images. Large avalanches clear swaths of forest that remain visible for decades. We compare historical maps, old photographs, chronicles and aerial images with modern satellite data. In Switzerland, this includes Johann Coaz’s historic avalanche maps from 1910, which document more than 10,000 avalanche tracks. Together, these sources reveal past avalanche paths, including those now overgrown with forest, and show how forest cover has changed.

Computer simulations. Using RAMMS, an avalanche dynamics software developed at the WSL Institute for Snow and Avalanche Research SLF in Davos, and complementary tools, we simulate how large avalanches move, how fast and how far they travel, and what forces they exert. We check the simulations against reconstructed real events, then use them to model different scenarios, including future climate conditions with more wet snow at high elevations.

Hazard mapping. Once verified for local conditions, these methods allow automated, large-scale hazard indication mapping for whole mountain regions. We will also compare the results with simpler, widely used terrain classification approaches such as ATES, which many skiers and mountaineers already know.

Sensors on trees. At selected sites we install tree movement sensors. They record how trees sway and respond when an avalanche hits them, and how impacts spread to neighboring trees. This helps improve how forests are represented in avalanche models.

Where we work