1. 1 Dilumie Abeysirigunawardena Climate Impact Researcher BC Ministry of Environment Ph.D. Candidate University of Victoria dilumie@uvic.ca or Dilumie.Abeysirigunawardena@gov.bc.ca Extreme Storm Surge and Wind-storm Climatology in the South coast of British Columbia RESULTS SUMMARY CIG Seminar Series, 29 th May 2008, University of Washington, USA

2. 2 The Objective Study the response of Extreme Sea levels and Windstorms to Natural Climate Variability

3. 3 Data (1) Pacific Region tide gauge stations Total Water level data (TWL) = Tide + Residuals List of Tide Gauge Stations (1) 7120-Victoria Harbour (2) 7277- Patricia Bay (3) 7735-Vancouver (4) 7795-Point Atkinson (5) 8074-Campbell River (6) 8408-Port Hardy (7) 8545-Bamfield (8) 8615-Tofino (9) 8735-Winter Harbour (10) 8976-Bella Bella (11) 9354-Prince Rupert (12) 9850-Queen Charlotte City

4. 4 Data A typical Tidal constituent table & Residual Time-series

5. 5 Directional Wind Data:  YVR - (1953-2006) (53-Years)  Sandhead - (1993-2006) (14-Years)  Saturna- (1993-2006) (14-Years) Data. Total Water level Data: al Pt. Atkinson - (1949-2006) (51yrs)

6. 6 Extreme Value Analysis Statistical Technique (Coles, 2001). Methodology.. TWL Extremes (i) Annual Maxima (GEV) Wind Extremes (ii) Peak over Threshold (GPD) μ = Location σ = Scale ξ = Shape Parameter Estimation For a given set of maxima the parameters are estimated via the Maximum Likelihood Estimation (MLE) method. The Extremes Toolkit (Gilleland and Katz (2005)

7. 7 Methodology Step 1 : Application of GEV to project Return Levels without Climate considerations: Project Return Levels based on the Annual Maxima Residuals. Generalised Extreme Value Distribution (GEV).

8. 8 Extreme Value Analysis in the presence of Climate Variability Covariates (X). Methodology. (μ, σ, ξ ) = f( X = MEI, PDO, NOI, ALPI, PNA) Location ParameterScale ParameterShape Parameter Effect of Natural Climate Variability on Extremes. Step 1: Identify the CV indices that shows significant improvement in the model fit with respect to the no-covariate case. Add each CV variable as Covariates in the Location(µ), Scale (σ) and shape ( ξ) parameter and test for significant model improvements through a Likelihood ratio test.

9. 9 Methodology Generalised Extreme Value Distribution (GEV). Step 2 : Investigate the influence of Cyclic Climate Variability Phenomena on return level projections: Station 7120 : Victoria Harbour

10. 10 Effect of Natural Climate Variability on Extremes. Most climate indices are closely related Redundancy test was performed Step 2: Systematically add each variable isolated in step (1) in to the model and eliminate the ones that does not improve the model fit significantly with respect to the former. Methodology

11. 11 Effect of Natural Climate Variability on Storm surge recurrences. Redundancy test Methodology NOI NOI + PNA Station 7120 : Victoria Harbour

12. 12 Effect of Natural Climate Variability on Storm surge recurrences. Final Model Consideration with CV effects after the redundancy test Methodology Station 7120 : Victoria Harbour μ (x) = 57.5 + 7.04(PNA)-2.28(NOI) σ (x) = 10.5 ξ(x) = -0.368

13. 13 Methodology. The definitions are based on the Environment Canada classification scheme. Step 3: Climate Indices Conditional on 3-dominant Climate State (i) Warm ENSO (ii) Neutral (iii) Cold ENSO Effect of Natural Climate Variability on Extremes.

14. 14 Results

15. 15 Climatic patterns governed by PNA, NOI and MEI has a significant influence on storm surge occurrences in the region. Results Sensitivity of Storm Surges to Climate Covariates

16. 16 Results Effect of Natural Climate Variability on Storm surge recurrences. Estimated return levels and 95% confidence intervals under ENSO conditions. Results for no climate consideration are included for comparison purposes Station 7120 : Victoria Harbour

17. 17 All stations indicate higher residual water- levels during warm ENSO episodes. Results Storm Surges with 1% exceedance in each year with CV effects 1 2 3 4 5 6 7 8 9 10 11

18. 18 Extreme Directional Wind recurrences with climate Covariates. Results.

19. 19 Directional Wind Recurrences at YVR with climate covariates. Results.

20. 20 Case Studies (i) December 16 th 1982 Extreme Event (ii) February 4 th 2006 Extreme Event

21. 21 December 16 th 1982 Storm Event examples of impacts… Damage to Mud Bay during 1982 flooding Damage to Westham Island Serpentine Dike Damage Damage along King George HWY in Surrey

22. 22 December 16 th 1982 Storm Event

23. 23 Results. Extreme TWL Recurrences With CV effects at Pt. Atkinson (1)(2)(3)(4)(5)(6)

24. 24 February 4 th 2006 Storm Event examples of impacts…

25. 25 February 4 th 2006 Storm Event : TWL Event

26. 26 February 4th 2006 Storm Event : Wind Direction

27. 27 February 4 th 2006 Storm Event : Wind Speed

28. 28 2006 event Recurrences viewed under Climate Variability Extreme TWL Recurrences and Extreme Storm Recurrences are not in phase Warm ENSO phase favors extreme TWL & Residuals Cold ENSO phase favors extreme windstorms

29. 29 Conclusions.. Climate Variability has significant effects on extreme sea levels and windstorm recurrences in Southern BC.  All stations in coastal BC indicate an increase in the Residuals during warm ENSO episodes.  Climatic patterns represented by PNA, NOI and MEI climate indices has a significant influence on storm surge occurrences in the region A Cold ENSO phase could result in more frequent windstorms in the study region Extreme TWL Recurrences and Extreme Wind-Storm Recurrences are not in phase in Southern BC.

30. 30 photo courtesy of Michael Brown Policy decisions are mainly driven by potential societal impacts resulting from climate variability and change, and not the climate change itself Changing extremes due to CC and CV effects are the most damaging Therefore it is strongly recommended to account for the effects of CC and CV in the analysis of Extremes leading to new policy decision for adaptation and design criteria. “ February 04 th 2006 Storm Impact at Boundary bay “ Picture provided by the Fraser Delta’s Engineering Department

31. 31 Acknowledgements Ben Kangasniemi, BC Ministry of Environment. Rick Thompson, Bill Crawford, Scott Tinis, IOS Sidney BC Eric Gilleland NCAR,Boulder CO, USA Bill Taylor and Mark Barton Environment Canada Trevor Murdock & Pacific Climate Impact Consortium Research Support & Contributions BC Ministry of Environment Environment Canada DFO & IOS Sidney BC Pacific Climate Impact Consortium (PCIC) National Center for Atmospheric Research (NCAR), USA Co-op Social Science University of Victoria BC Ministry of Labour and Citizens’ Services

32. 32 Thank you… feedback?