Intensity-Duration-Frequency Curve Update for Newfoundland and Labrador

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1 Intensity-Duration-Frequency Curve Update for Newfoundland and Labrador Allyson Bingeman 1 Juraj Cunderlik 1 Gerald Crane 2 Amir Ali Khan 3 1 GHD Limited 2 Office of Climate Change and Energy Efficiency (CCEE), Government of Newfoundland and Labrador 3 Water Resources Management Division, Government of Newfoundland and Labrador

2 Intensity-Duration-Frequency (IDF) Curves Most recent Environment Canada IDF curves: V2.3 (released 2015) Based on annual precipitation maxima Multiple uses: Infrastructure design Stormwater systems Floodplain mapping Image source: Environment Canada (EC) IDF curves, V2.3, 2015

3 Climate Change Multiple effects Decreasing snow cover, earlier and more frequent snowmelt Increase in intensity and frequency of storms and cyclones Increase in frequency and magnitude of floods and storm surges GCM modeling for Newfoundland and Labrador: Newfoundland: mm/day (winter) Labrador: mm/day (summer) Return period of 24-hr events reduced by a factor of 2 by end of century Image source: CCEE

4 Image source: CCEE

5 Active/Inactive IDF curves Province/ Territory # of IDF Curves # of Active IDF Curves 1 Across Canada, numerous IDF stations are no longer recording precipitation Not capturing emerging effects of climate change IDF Curves are missing: Increasing trends Recent severe precipitation events Potential for underestimation Result: Safety implications Problem! BC AB 30 7 SK 35 4 MB 27 7 ON QC NB 14 6 PE 3 3 NS 15 7 NL 19 6 YT 9 2 NT 7 2 NU IDF Curve includes data for 2010 and later

6 IDF Update Newfoundland and Labrador identified climate change as a concern in the Province s 2011 Climate Change Action Plan 13 IDF stations are inactive Recent climate not captured for the Province Coarse monitoring network & inactive stations leads to IDF underestimation Perform IDF Update Purposes Update inactive IDF curves using other precipitation data sources Develop future climate IDF curves for the Province

7 Update Methodology Select stations QA/QC Multiple factors: topography, weather patterns, precipitation measurement methods, distance, temporal duration(s) Consistency with IDF data, nearby stations, other durations Remove snow events, raw data Test Check for homogeneity between IDF data and update data Mean, standard deviation, shape of distribution Update Combine data and test goodness of fit to Gumbel distribution Perform Gumbel analysis, produce EC IDF graphs and tables

8 Results of Update Most stations showed increases in IDF precipitation estimates Regional pattern Labrador Northeast Newfoundland Southwest Newfoundland Updated IDF curves matched recent precipitation patterns Many large increases in precipitation (>5%) Most increasing trends not statistically significant

9 Future Climate IDF Curves Observed Data IDF curves No conclusive evidence of statistically significant trends in observed data Precipitation is increasing in many locations (not all) Climate Modelling Global Climate Models (GCM) Consistent increase in precipitation extremes Magnitude and frequency of extreme events Problem Develop IDF curves based on GCM results Need to downscale GCM results Lack of regional climate model data; statistical methods often used Statistical downscaling methods depend on current precipitation information Image source: CCEE

10 IDF-CC Tool New tool for deriving future climate IDFs developed at University of Western Ontario in partnership with Institute for Catastrophic Loss Reduction and Insurance Bureau of Canada Uses the latest Intergovernmental Panel on Climate Change (IPCC) future climate scenarios (IPCC Annual Report 5, 2013) Representative Concentration Pathway (RCP) scenarios 2.6, 4.5, 8.5 Develops statistical model between GCMs and observed data that relates cumulative PDFs 22 GCMs available GCMs/scenarios/time horizons can be manually selected by user Ensemble and maximum/minimum projections can be constructed

11 IDF-CC Results RCP 4.5 Ensemble method : 12% : 20% : 24% Current 100-year event becomes the 25-year event by

12 IDF-CC Uncertainty Horizon Average (all durations and return periods) Minimum projection less than current IDF for some stations/ durations/ return periods Average range (all stations): %

13 Effect of Updated IDF Produced future IDF curve for both original and updated St. John s A IDF curve Current and future precipitation estimates Decreased for short durations Increased for long durations Future climate IDF curves may be underestimated if IDF curve is out-of-date Duration % Change in IDF 1 % Change in Future Climate IDF 1 5-min min min min hr hr hr hr hr Average percent change for all IDF return periods

14 Conclusions Performing an IDF curve update has multiple benefits Out-of-date IDF curves do not include recent changes in precipitation Even if trends in observed data are not statistically significant, can result in significant increases in precipitation estimates (>5%) Estimates of future climate precipitation are impacted by out-of-date IDF curves Source: Sample Flood Risk Map with Climate Change, Stephenville, 2009, CCEE Increased safety for municipal infrastructure design Increased safety for future climate precipitation estimates NL is one of the first jurisdictions in the world to incorporate climate change into flood risk mapping studies.

15 Presenter contact information Allyson Bingeman Juraj Cunderlik