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Identifying Risk Areas for Landslides

This study identifies risk areas for landslides and categorizes main causes, driving factors, triggering mechanisms, and affected soil variables. It discusses landslide classifications, main soil variables impacted by landslides, and different tiers of assessment approaches. Recommendations include intensifying collaboration with EuroGeoSurveys and emphasizing qualitative approaches. Current challenges in harmonization due to lack of standardized methodologies and incomplete inventories are also highlighted.

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Identifying Risk Areas for Landslides

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  1. Identifying Risk Areas for Landslides Florence Carre (JRC, Subgroup leader), D. Seebach, N. Filippi, M. Pizziolo, G. Bertolini, A. Poschinger, J. Fortuny-Guasch, M. Gemmer

  2. LANDSLIDE Movement of a mass of rock, debris, earth down a slope (Cruden & Varnes, 1996) LANDSLIDE CLASSIFICATION (Cruden & Varnes, 1996)

  3. MAIN CAUSES Snow melt and heavy rainfall events  water saturation DRIVING FACTORS RELATED TO VULNERABILITY OF SOIL • Geology/bedrock material • Slope • Land cover • Soil permeability TRIGGERING MECHANISMS • Rapid snowmelt • Intense rainfall • Water level change • Human activities • Changes in landuse/land cover • Earthquakes / volcanic eruption

  4. Loss of soil functions and increase of soil vulnerability to other threats MAIN SOIL VARIABLES AFFECTED BY LANDSLIDES Affected soil physical properties: - structure; - bulk density; - water permeability; - erosion - soil organic matter decline - compaction (but also as a driving factor)

  5. Tier I Source: EPSON (European Spatial Planning Observation Network) project http://www.gtk.fi/projects/espon/Landslides.htm

  6. Tier II approach Usually 3 scale maps (Van Westen, 1993) • Synoptic or territorial scale maps (> 1:50,000): inventories maps used by planning agencies to direct allocation of funds, develop emergency preparedness plans and similar tasks • Medium scale maps (> 1:20,000 to 1: 1:50,000): used for preliminary or regional landslide hazard assessments and feasibility studies followed by more detailed work • Detailed scale maps (> 1:5,000 to 1: 1:500): Prepared as part of a landslide hazard assessment of a specific site and should be accurate enough to guide layout of individual structures or specific operations or to plan mitigation

  7. Common criteria (1) Common criteria to delineate landslide risks - Spatial probability of occurrence of landslides (like density of landslide/km²) - For tier I approach, landslides have to be defined in a common way by all the MS in order to compare the density - For tier II approach, the 3 scale maps can be produced according to the purpose

  8. Common criteria (2)

  9. Conclusions • Intensify collaboration with EuroGeoSurveys (EGS) • Elaborate on qualitative approach, since no operational approach has been presented Today’s problems • Improvements in harmonisation are necessary because: - inventories do not follow any commonly agreed standards or methodologies until now - authorities in charge of inventories are either local, regional or national and can be civil engineers, soil scientists or geologists • Only landslides related to civil damages are listed, others can exist and not be listed (above all in unpopulated areas)

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