The Importance of Rockfall and Landslide Risks on Swiss National Roads

To obtain standardized information on the type, frequency, intensity and location of natural hazards that threaten national roads, the federal roads office FEDRO initiate a Swiss-wide project in 2008. This paper presents the methodology used in this project and presents a summary of the monetarised risks of the evaluated road sections. The natural hazards that need to be assessed are snow avalanches, rock- and icefall, flooding, debris flows, landslides (permanent, spontaneous and slope type debris flows) and collapse dolines. Risk hot spots mainly occur due to road closure related to rockfall or bank erosion. Damage to infrastructure represents generally only up to 20 % of the total calculated risk; person risks (casualties) add up to 8 % of the total risk. Rockfall is responsible for 35 % of the total calculated risk, rock avalanches for 8 %, permanent landslides for 5 %, spontaneous landslides for 3 % and slope-type debris flows for 1 %.