YELGIP Workshop, Maribor, January 18th 2011Making Cities Resilient, 26-28 May 2015

Landslide risks in the Göta River Valley in a changing climate

Exchange New Orleans - Gothenburg

Bo Lind, Swedish Geotechnical Institute

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Glaciated landscape with soft sediments (silt-clay)

Valleys andLow-lands

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Göta 1957

Tuve 1977

Vagnhärad 1997

Småröd 2006

Post-glacial rebound – Erosion and landslides

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Landslides and mudflows in Sweden

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Dynamic landscape of landslide scars

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The Göta river valley

• Large run-off area• Source of water supply for 8% of the population• Important infrastructure and settlements• Sensitive to landslides

Run-off area

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Catastrophic consequences of landslides

Foto: Thomas Samuelsson

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Landslide retrogression in areas with highly sensitive clay

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Relative change in precipitation for a period of 30-years i the Vänerns runoff area (moving average)

Vänern - Ändring av nederbörd

-5

0

5

10

15

20

25

30

35

40

1960 1970 1980 1990 2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100

År

Del

ta P

[%

]

SMHI-E5:1-50-A1B SMHI-E5:3-50-A1B KNMI-E5:3-25-A1B MPI-E5:3-25-A1B

CNRM-ARPEGE-25-A1B METNO-BCM-25-A1B C4I-HC:Q16-25-A1B C4I-E5:3-25-A2

HC-HC:Q0-25-A1B SMHI-CCSM3-50-A1B SMHI-CNRM-50-A1B SMHI-E5:1-50-B1

SMHI-E5:2-50-A1B SMHI-E5:3-25-A1B Medel

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“In order to address forthcoming climate changes and handle increased flow in the Göta River, greater understanding is required of the stability conditions along the entire Göta River. The funding is to be used for the improvement and production of landslide analyses and stability mapping along the Göta River.”

Mapping of landslide risks - The Government's commission

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Landslides in a changing climate

• Driving forces affected by: Increased groundwater pressure – climate related Flow and river erosion – climate related Loading by houses and infrastructure – development

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Field and laboratory investigations

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• Extension of quick clays• Geometry of the river• Groundwater modelling• Erosion• Consequences

Methodology

Bild: SjöfartsverketLifeBuildingsIndustryEnergy supplyWater supplyRoads and railroadsShippingContaminated sediments

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1.01

1.1

1.35

1.6

S4S3S2S1

LLW+9.31

3

10 kPa 5 kPaGC-v ägIndustriområde

Stability calculation

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probability

Statistical analysisStability factorAmount of dataUncertainty

consequence

Valuation/CalculationLifeBuildingsIndustryEnergy supplyWater supplyRoads and railroadsShippingContaminated sediments

Level of risk

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Current conditions: - Many areas with high risk (red)- High risk also in built-up areas- Large areas with poor stability closest to the river and conditions for large landslides

Future conditions:- Climate change means that the risks increase - The area with the highest risk level (red) increases 10%- The probability of landslides further increases in high-risk areas - unless action is taken

Conclusions

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Suggestions

• Necessary to take actions to reduce the current landslide risks which also provide opportunities for increased flows in the future

• The estimated cost for the entire Gota River and the Northern River:4-5 billion SEK at today's maximum flows5-6 billion SEK for increased maximum flows

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Example of what can be done

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GIS platform

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Thank you