Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Nat. Hazards Earth Syst. Sci., 3, 435-442, 2003
https://doi.org/10.5194/nhess-3-435-2003
© Author(s) 2003. This work is licensed under
the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.
 
31 Oct 2003
Rockfall hazard mapping along a mountainous road in Switzerland using a GIS-based parameter rating approach
F. Baillifard2,1, M. Jaboyedoff3,1, and M. Sartori4,1 1CREALP – Research Center on Alpine Environment, Industrie 45, 1951 Sion, Switzerland
2Institute of Geology and Paleontology, University of Lausanne, BFSH2, 1015 Lausanne, Switzerland
3Quanterra, Chemin Tour-Grise 28, 1007 Lausanne, Switzerland
4Department of Geology and Paleontology, University of Geneva, Maraîchers 13, 1211 Genève 4, Switzerland
Abstract. A posteriori studies of rock slope instabilities generally show that rockfalls do not occur at random locations: the failure zone can be classified as sensitive from geomorphological evidence. Zones susceptible to failure can there-fore be detected. Effects resulting from degrading and triggering factors, such as groundwater circulation and freeze and thaw cycles, must then be assessed in order to evaluate the probability of failure. A simple method to detect rock slope instabilities was tested in a study involving a 2000 m3 rockfall that obstructed a mountainous road near Sion (Switzerland) on 9 January 2001. In order to locate areas from which a rock-fall might originate, areas were assessed with respect to the presence or absence of five criteria: (1) a fault, (2) a scree slope within a short distance, (3) a rocky cliff, (4) a steep slope, and (5) a road. These criteria were integrated into a Geographic Information System (GIS) using existing topo-graphic, geomorphological, and geological vector and raster digital data. The proposed model yields a rating from 0 to 5, and gives a relative hazard map. Areas yielding a high relative hazard have to meet two additional criteria if they are to be considered as locations from which a rockfall might originate: (1) the local structural pattern has to be unfavourable, and (2) the morphology has to be susceptible to the effects of degrading and triggering factors. The rockfall of 9 January 2001, has a score of 5. Applied to the entire length of the road (4 km), the present method reveals two additional areas with a high relative hazard, and allows the detection of the main instabilities of the site.

Citation: Baillifard, F., Jaboyedoff, M., and Sartori, M.: Rockfall hazard mapping along a mountainous road in Switzerland using a GIS-based parameter rating approach, Nat. Hazards Earth Syst. Sci., 3, 435-442, https://doi.org/10.5194/nhess-3-435-2003, 2003.
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