Potential Impacts of Climate Change on Stormwater Management. Ed Watt, Mike Hulley & George Zukovs

Transcription

1 Potential Impacts of Climate Change on Stormwater Management Ed Watt, Mike Hulley & George Zukovs

2 Presentation Outline Plausible Scenarios of Climate Change Stormwater Management A Brief History Climate Change Potential Implications Key Climate Variables for SWM Planning & Design Approaches to Mitigate Adverse Impacts Conclusion

3 Plausible Scenarios of Climate Change - IPCC Climate change: natural vs. anthropogenic Changes atmospheric CO 2 Expected change: the IPCC results Basis for predictions Concept of uncertainty Temperature Precipitation

4 Natural Climate Change Ice age cycle (~100,000 years) 20,000 years ago

5 Atmospheric CO 2 Last 20,000 years Next 100 years

6 Intergovernmental Panel on Climate Change IPCC UN sponsored body formed about 20 years ago. Three working groups: WG1: Scientific Assessment WG2: Impacts on Natural Environment WG3: Mitigative and Adaptive Strategies

7 Temperature Projections The annual mean warming is likely to exceed the global mean warming. Seasonally, warming is likely to be largest in winter. Minimum winter temperatures are likely to increase. IPCC Likelihood Scale Very likely > 90% probability Likely > 66% probability

8 Temperature Projections +/- 5 o C

9 Temperature Projections

10 Temperature Projections Changes in March Snow Cover

11 Temperature Projections Changes in Ice Cover: Greenland

12 Precipitation Projections Annual mean precipitation is very likely to increase. In southern Canada, precipitation is likely to decrease in summer. Snow season length and snow depth are very likely to decrease. In the northernmost part of Canada maximum snow depth is likely to increase. IPCC Likelihood Scale Very likely > 90% probability Likely > 66% probability

13 Precipitation Projections Precipitation Intensity (Annual Precipitation/Number of Wet Days)

14 Precipitation Projections Average Number of Dry Days/Year

15 Basis of Projections?

16 Plausible Scenarios of Climate Change - IPCC Despite relatively large uncertainty for climate change projections: Large increases in atmospheric CO 2 will result (very likely) in an increase in mean annual temperature. More intense, less frequent, rainfall events are likely in the future. Lower snowpack depths (very likely) will impact seasonal availability of water.

17 SWM A Brief History Urban infrastructure & SWM today (& for foreseeable future) reflects approaches over past 100+ years Define 4 eras when the problem, solution and tools varied.

18 Storm Sewer Era (~ ) Newark Vancouver (~1900)

19 SWM Era (~ ) Cataraqui Pond, Kingston

20 Urban Stormwater BMP Era (~ )

21 Future Eras? Observation SWM has not been static & there is no reason to expect that we have reached the ultimate solution Emerging approaches Preservation of the pre-development water balance stormwater reuse

22 Climate Change Potential Implications Sensitivity of SW infrastructure to CC depends on i) magnitude of expected change & ii) type of infrastructure Types include Transmission structures Management structures for quantity control Storage structures for quality control CSO abatement structures

23 New SWM Infrastructure Design pipe diameter will increase with increased design rainfall Required live storage of quantity control structures will increase Required storage volume of quality control will increase, but design value may not increase (provincial guidelines) Size of CSO abatement structures

24 Maintenance of Existing SWM Infrastructure Increase in rainfall severity may force more frequent maintenance for storage structures But, maintenance may be relatively insensitive to modest impacts of CC

25 Retrofit of Existing SWM Infrastructure Unlikely that perceived CC alone will lead to significant retrofitting However, when retrofitting is planned for any reason, design criteria should be revised to account for the potential impacts of CC

26 Externalities Property owners & insurance companies incur damage costs Provincial governments fund flood & erosion control projects Environmental impacts are not considered a cost, but rather a fuzzy constraint All of these may become more severe

27 Impacts of Non-climatic Factors Deterioration of existing infrastructure Population growth New models for financing infrastructure New provincial standards for SW loadings New models for SW pricing Changing public expectation Evolving public attitudes

28 Impacts of Non-climatic Factors These factors may have impacts of similar or greater impact than climate change Need to consider their evolution their role in exacerbating or ameliorating the effects of CC

29 Planning & Design Approaches to Mitigate Adverse Impacts Examine design criteria &methodology View CC as an additional uncertainty Relate design criteria to uncertainty Consider adaptive planning & design

30 Critically Examine Design Criteria & Methodology Design return periods have not changed in many years & may not reflect current or future risk of damage In many cases, methodology does not reflect advances in science or best available technology

31 View Climate Change as an Additional Uncertainty Consider potential impacts of CC as one of several uncertainties Other uncertainties include future population growth, new standards, new financing models, changing public expectations, evolving attitudes towards the natural environment +/-

32 Explicitly Relate Design Criteria to Uncertainty/Risk In other civil engineering fields, design criteria are explicitly related to uncertainty, e.g. safety factors In stormwater management, design criteria are fixed regardless of uncertainty level Why? Is this appropriate?

33 Consider Adaptive Planning & Design Insofar as possible, maintain flexibility Facilitate revision of design criteria Revise plans as design criteria and methodology evolve Provide some overcapacity as a hedge against increased rainfall

34 Conclusion Accept a Non-stationary Climate Prioritize Relevant Infrastructure Issues Review Design Standards Conduct Risk Analyses