Artouste, France: Rock fall

The hazard at Artouste is caused by rockfall, sourced from both exposed rock ledges and loose blocks resting on the steep till-covered slope. The site is adjacent to the hydropower dam of Artouste, where the RD-934 road descends in sharp turns from the height of the reservoir level to the base of the dam. The forest has a protective effect for smaller blocks, but rocks often hit the road. In 2013, a fatal accident occurred when a passing car was hit by a falling rock.

The main problem to solve with the implemented NbS measures is to reduce rockfall on the road.

Through the H2020 project PHUSICOS wooden structures designed to prevent the release of rocks and to stop released rocks before they reach too high a velocity have been implemented. 

• Large upscaling potential
• Economic gain, through less need for repair of the road, and the less need for maintenance compared to traditional engineered measures
• Local jobs with construction of the measures, with more to come regarding potential for upscaling
• Reduced fear among the users of the road, and more secure transport of goods and people, also important for the tourist industry of the area

The implemented NbS interventions consist of different structures made by wood and/or local stones. The solutions rely on active measures (manual stabilization and/or timber structures) to stabilize the source areas and passive measures (mixed wood and/or stone structures) to slow down and/or divert rocks in their trajectories enhancing the protective role of the forest.

The logs used are taken from local forests (not in the Artouste slope, though). They are moisture-protected in the lower ends, anchored in the ground by long iron rods and either bolted or tied together in the top ends . Each structure is designed individually for the individual block or ledge they stabilize.

After the material was in place on the slope all structures are built by hand to avoid any use of heavy machinery on the ground.

Many mountain regions on the northern hemisphere, which were glaciated during the last glaciation expose large areas of steep slopes covered by glacial till. Hence, there are potentially numerous areas with conditions like those at Artouste, with surficial boulders, either glacial erratics or rockfall blocks, and exposed bedrock ledges from which blocks can be released. Consequently, the potential for using similar techniques is huge

 The wooden structures for rockfall protection have been implemented through the H2020 project PHUSICOS.

NbS actions in the Pyrenees demonstrator case site are organized through the Consorcio de la Comunidad de Trabajo de los Pirineos (CTP). However, the individual interventions are proposed and organized by different regional organizations, on both the Spanish and the French side