Landslide susceptibility mapping along pipeline corridors in Canada. Andrée Blais-Stevens Réjean Couture

Transcription

1 Landslide susceptibility mapping along pipeline corridors in Canada Andrée Blais-Stevens Réjean Couture

2 2 Outline Pipelines in Canada Two regional studies: Northwest Territories & British Columbia Future activity: Yukon Alaska Highway Pipeline Present activity: Sea to Sky Highway, BC (road to the next winter Olympics in 2010) Conclusion

3 Oil Pipelines in Canada 3 Source: CEPA ~ km pipeline in Canada

4 Gas Pipelines in Canada 4 Source: CEPA Safe and efficient means of transporting oil & gas

5 Proposed new pipelines 5 Yukon NWT Source: CEPA National Energy Board of Canada allows implementation only after Environmental Assessment

6 6 Regional landslide susceptibility mapping studies Yukon Alaska Pipeline Project Literature review (2) One for existing pipeline in British Columbia (Terasen Gas) and the other for a proposed pipeline (Mackenzie Valley Gas Pipeline)

7 7 Landslide susceptibility for an existing pipeline, (Terasen Ltd.), British Columbia BGC semi-quantitative regional study based on expert judgement; Leir et al, 2004 Purpose: identify slow progressive subsurface deformation for buried gas pipeline that could cause leakage and affect 88 communities Area: 54k km 2 ; 17, 1:250k map areas; 86 M pixels Landslide types: earth and debris slides, earth and rock flows, and earth and rock creep Parameters: bedrock type, surficial geology, slope angle, proximity to water bodies, and proximity to faults

8 8 Terasen gas pipeline Methodology: Parameters classified by experts British Columbia Map area Community Semi-quantitative using fuzzy logic= probabilistic without direct use of inventory Landslide inventory used to calibrate GIS model

9 9 Vancouver ~66% of landslides fall >0.54 threshold =successful (Guzzetti et al. 1999)

10 10 Landslide susceptibility for a proposed pipeline Mackenzie Valley Pipeline Study area 540 km X 40 km corridor; =24k km 2 area Area of widespread landsliding 99% vegetation cover permafrost ubiquitous Low relief; max elevation 402 m Couture & Riopel 2008

11 11 Mackenzie Valley Pipeline Methodology Landslide inventory >1800 landslide events Landslide types: Mainly retrogressive thaw flows, active layer detachments; Some rock falls, earth slides, and retrogressive thaw slides Qualitative parametric method based on expert judgement

12 12 MVP Methodology Parameters: land cover (L1), slope angle (S1), slope aspect (S2), surficial geology (G), permafrost type (P1), permafrost content (P2) Each layer re-classified Ranks assigned to re-classified units 1-10 Susceptibility Index (SI)= 0.3S1+ 0.5S2+0.3G+ 0.05P1+ 0.2P2+0.1L Results: Landslides 20%H 56%M 8%L; somewhat successful Conclusion: Should likely separate landslide types for better validation

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14 14 Comparison Both studies relied on expert judgement to give weights to the parameters One method more quantitative; more successful likely because fewer types of landslides involved Both mentioned that better quality of initial data would have improved their results Better choice of parameters could improve their results

15 15 Yukon Alaska Highway pipeline Future work Inventory & development of methodology for landslide susceptibility Alaska Highway

16 16 Sea to Sky Highway transportation corridor Landslide Inventory and surficial geology maps completed Developing landslide susceptibility methodology Applying two parametric equations separating the two most common types of landslides; rock falls and debris flows

17 17 Sea to Sky Highway road to 2010 winter Olympics

18 18 Landslide distribution 155 landslides in last 150 yrs Highest concentration between Horseshoe Bay and Porteau Cove

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20 20 Conclusion Massive growing network of pipelines in Canada NEB implements and regulates pipelines only after Environmental assessment(s) which include slope stability analyses Very few regional landslide susceptibility studies are available; Terasen pipeline and Mackenzie Valley pipeline Semi-quantitative to qualitative likely because the parameters need to be broad in such a large area where detailed data are scarce Present (Sea to Sky Hwy) and future work Yukon Alaska Hwy pipeline= development of landslide susceptibility studies

21 21 Khyex River landslide Sutherland River landslide