Soil Information Working Group (SIWG) ESBN Plenary, London, 2005 Identifying Risk Areas for Landslides Florence Carre (JRC, Subgroup leader), D. Seebach,

Soil Information Working Group (SIWG) ESBN Plenary, London, 2005

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


LANDSLIDEMovement of a mass of rock, debris, earth down a slope (Cruden & Varnes, 1996)

LANDSLIDE CLASSIFICATION

TYPES OF MOVEMENT

TYPE OF MATERIAL

Bedrock

Soils

Coarse Grained Soil

Fine Grained Soil

Falls Rock fall Debris fall Earth fall

Topples Rock topple Debris topple Earth topple

SlidesRotational

Rock slide Debris slide Earth slideTranslational

Lateral spreadsRock

spreadDebris spread Earth spread

Flows Rock flow Debris flow Earth flow

Complex: Combination of two or more types of movement

(Cruden & Varnes, 1996)


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


MAIN SOIL VARIABLES AFFECTED BY LANDSLIDES

Affected soil physical properties:

- structure;

- bulk density;

- water permeability;

Loss of soil functions and increase of soil vulnerability to other threats

- erosion

- soil organic matter decline

- compaction (but also as a driving factor)


Tier ISource: EPSON (European Spatial Planning Observation Network) projecthttp://www.gtk.fi/projects/espon/Landslides.htm


Tier II approachTier II approach

• 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

Usually 3 scale maps (Van Westen, 1993)

• 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


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


Common criteria (2)Common criteria Data source/type of

informationData Quality /Resolution

Tier 1 Tier 2

occurrence/density of existing landslides

statistics NUTS IIIlarger-scale regional/local assessments

bedrock

nature of material + presence of fissures and poresSensitive bedrocks can be Gault Clay and Flish

Map of Geology 1:1,000,000

higher resolution maps

soil properties texture, structure, permeability

not required for in Tier 1

classification/grouping according to?

slope classes: 0-10°; 10°-30°; >30° 250m same or higher

land cover/land useinfrastructure; cultivation density/pressure, mining

Non relevant for Tier 1

100m

climatelikelihood of heavy rainfall events

daily events (e.g. < 10, 10-70, >70 mm/day)

same or higher

seismic risk threshold? threshold?


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)

Documents

Soil Information Working Group (SIWG) ESBN Plenary, London, 2005 Identifying Risk Areas for Landslides Florence Carre (JRC, Subgroup leader), D. Seebach,