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Lost Rivers & Urban Flooding, Media, Myths & Smart Mitigation - Toronto Wards 13 / 14 - Presentation to Green 13

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Presentation to Toronto Ward 13's Green 13 on urban flooding and risk factors including lost rivers, urbanization and intensification, and critical review of extreme rainfall intensity trends that are decreasing in Toronto and southern Ontario based on Environment and Climate Change Canada's Engineering Climate Datasets (version 2.3). Media myths regarding flooding are exposed including the GO Train flood of July 8, 2013 that was not unprecedented but was rather a low risk flood event that has occurred frequently in the past and the insurance industry discredited claims in "Telling the Weather Story" that weather that used to happen every 40 years is happening every 6 years. The economics of green infrastructure, low impact development measures, are evaluated including representative project costs and are shown to be unaffordable for widespread implementation in Wards 13 / 14. 3D Arc Scene images of Toronto lost rivers are illustrated across the city and within the historical Wendigo Creek and Spring Creeks in Ward 12 (aka lost rivers). Variations in reported basement flood density show lower flood risk in the Ward 13 combined sewer catchment (consistent with Toronto wide trends), and show higher reported flood density in partially separated sewer catchments.

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Lost Rivers & Urban Flooding, Media, Myths & Smart Mitigation - Toronto Wards 13 / 14 - Presentation to Green 13

  1. 1. WENDIGO WHERE’D IT GO ? LOST RIVERS AND URBAN FLOODING: MEDIA, MYTHS & SMART MITIGATION Robert Muir, M.A.SC., P.Eng. Green 13 – January 17, 2018
  2. 2. OUTLINE •Lost Rivers and Urban Flooding •Ward 13 and 14 Flood Risks •Extreme Rainfall Trends – Media Myths •Urbanization & Intensification Stresses 2
  3. 3. WHO AM I ? •Manager, Stormwater @ City of Markham •Previously a Partner at Dillon Consulting •Blogger: www.cityfloodmap.com •Podcast: Open During Construction •Hobbies: flood mapping, extreme
  4. 4. SEVERE FLOOD EVENTS - TORONTO MAY 12, 2000 3162 REPORTS AUGUST 19, 2005 3640 REPORTS JULY 8, 2013 1934 REPORTS(sample of 4700 total) 4
  5. 5. TORONTO
  6. 6. Valleys & Flood Hazards
  7. 7. Overland Flow beyond the Valleys
  8. 8. Even More Overland Flow
  9. 9. FLOOD LOCATION - VALLEY vs TABLE LAND 3162 REPORTS 2.0 % 98 % 3640 REPORTS 0.6 % 99 % 1934 REPORTS* 2.8 % 97 % Flooded Properties within Regulated Valley Area : 5.1 – 7.3 % (includes River Flood Vulnerable Areas) Properties in River Flood Vulnerable Areas : Properties On Table Land (beyond vulnerable areas) : MAY 12, 2000 AUGUST 19, 2005 JULY 8, 2013 9
  10. 10. Wards 13 & 14
  11. 11. Regulated Valley Features
  12. 12. Overland Flow Paths
  13. 13. Overland Flow Spread (Estimated)
  14. 14. Flood Reports Ward 13 & 14 (approx.)
  15. 15. Flood Reports Other Areas (higher risks)
  16. 16. Wendigo Creek Spring Creek
  17. 17. • “…the Insurance Bureau of Canada estimates that extreme storms of a magnitude expected to happen every 40 years are now predicted to occur every six years.” • This statement has been: ▫ Refuted by Environment and Climate Change Canada ▫ Advertising Standards Canada has resolved 3 complaint cases resulting in the removal of this statement from prominent insurer web sites and marketing materials since 2015 Media and marketing myths on extreme weather Origin (2012; video on next slide) 17
  18. 18. Environment and Climate Change Canada Refutation of Claim: 18
  19. 19. 19 A: “If this is used as the basis for statements about actual changes in extreme rainfall in Canada, then I would have concerns. Alex J. Cannon, Ph.D. Research Scientist, Climate Data and Analysis Section, Science and Technology Branch Environment and Climate Change Canada / Government of Canada Q: “Can you comment on one last thing which is the statement by ICLR/IBC that ECCC data already shows a 1-standard deviation shift in extreme weather, with 40 year storms happening every 6 years, assuming weather follows a standard normal probability density function?” Robert J. Muir, M.A.Sc., P.Eng. Manager, Stormwater Environmental Services Department City of Markham 04 January 2018 Exchange with Environment Canada
  20. 20. • Maximum rainfall intensities decreasing in certain areas • Decreasing trends in Toronto are statistically significant over 6 to 24 hour rainfall durations • Same trends in Southern Ontario … rain stresses not increasing. The Data 20
  21. 21. • Toronto Future Climate Drivers Study predicted changes in rainfall extremes that are contradicted by observed stable values in extreme rainfall Extreme Rainfall Volumes (mm) SENES Baseline Predicted Environment Canada Data 2000-2009 2040-2049 1940-1990 1940-2007 1940-2017* • 100 year Max. Daily 81 204 95.9 94.7 96.8 • 10 year Max. Daily 62 135 68.8 67.6 68.9 • 10 year Max. Hourly 20 39 39.8 38.5 39.5 * Update by City of Markham using ECCC raw data to Sept 15, 2017 Predicted Extremes vs. Observed Trends 21 Rain extremes predicted to ‘go up’ are actually ‘flat’
  22. 22. www.cityfloodmap.com Less Extreme Rain at Many Ontario Stations • Stations with 45+ years of record and recent data. • More rain decreases than rain increases. • S. Ont. twice as many significant decreases. http://www.cityfloodmap.com/2016/01/climate-change-ontario-short-duration.html Significant Decr. Decrease Increase Significant Incr. Source: Environment Canada Engineering Climate Dataset ftp://ftp.tor.ec.gc.ca/Pub/Engineering_Climate_Dataset/IDF/ Idf_v2-3_2014_12_21_trends.txt in IDF_Additional_Additionnel_v2.30.zip 22
  23. 23. Media “Root Cause” Data Gaps • Operational issues mis-characterized as a climate change-induced event. • Reported “unprecedented” conditions contradict past data & reports. 23http://www.cityfloodmap.com/2015/12/stranded-metrolinx-go-train-avoidable.html July 8, 2013 Stranded GO Train Toronto’s Don River May 28, 2013 Greater Flood Weeks Before Operational Risk Overlooked Less than 5 Year Flow =
  24. 24. We’ve seen this before… 24http://www.cityfloodmap.com/2017/05/go-train-flooded-in-1981-too-media.html =
  25. 25. 25 25
  26. 26. SO WHAT IS CAUSING MORE FLOODING? •Urbanization and intensification •Only Milli Vanilli Blame it on the Rain 26
  27. 27. 50 YEARS OF URBANIZATION 27
  28. 28. Urban ‘Pink Splat’… like Cat in the Hat … don’t think we’ll get old hydrology back. 28
  29. 29. INTENSIFICATION ON MY STREET •45 yrs adding hard surfaces = more runoff for the same rain Example intensification, just the 8 addresses north of me since the late 1970's ... add it 29
  30. 30. WHAT IS INCREASING RIVER FLOW ? •University of Guelph research says urbanization and not changing climate 30
  31. 31. Upper Decile of 𝐑𝐮𝐧𝐨𝐟𝐟 𝐂𝐨𝐞𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐭𝐬 Moira River at Foxboro (02HL001): 1921-30, 1963-72, 2006-15 Don River at Todmorden (02HC024): 1963-72 Don River at Todmorden (02HC024): 2006-15 0.0 0.2 0.4 0.6 0.8 1.0 Mar Apr May Jun Jul Aug Sep Oct Nov RunoffCoefficient Month Rural condition 0.0 0.2 0.4 0.6 0.8 1.0 Early urbanization 0.0 0.2 0.4 0.6 0.8 1.0 Significant urbanization
  32. 32. GREEN INFRASTRUCTURE•Helps mimic natural hydrologic cycle, reduce runoff •2017 WWFMP implementation update, Toronto Water states implementation issues: “Design and implementation issues concerning the installation of green infrastructure in an urban municipality can impact the construction of green infrastructure projects.” 32
  33. 33. Completed Project Costs – Typically Very High 33 City / Town LID Type (Project Name) Capital + Soft Cost ($) Service Area (ha) Cost / Hectare * Markham Bioswale & Infiltration Trench (Green Road) $ 783,602 1.90 $412,422 + Markham Rain Garden (Glencrest Park) $216,000 1.6 ** $135,000 Brampton Bioswale (County Court SNAP) $130, 514 0.2 $652,570 + Whitchurch- Stouffville Various Measures (Coultic Park & CC Parking Lot) $103,026 0.11 $936,600 Ottawa Bioretention (Sunnyside / Road) $282,887 0.464 $609,670 Ottawa Bioswale (Stewart / Road) $363,452 2.010 $180,821 Ajax Rain Garden (Lake Driveway) $350,000 0.14 $2,500,000 Mississauga Bioswale & Pavers (Elm Drive) $226,000 0.633 $357,030 Mississauga Bioswale (Lakeview) $420,900 1.6 $363,063 Median Unit Cost = $412,000 / ha * Range similar to TRIECA 2017 examples ** No impervious hectares
  34. 34. reen Infrastructure Cost for 1050 ha = $420,000,000 1050 hectares
  35. 35. CONCLUSIONS • Bad News: Lost Rivers often have concentrated flooding risks • Good News: Wards 13 and 14 have relatively low risks • Bad News: Urbanization & intensification have increased runoff • Good News: Rain extremes have not changed • Green infrastructure would be expensive mitigation and not cost effective … perhaps consider in only as isolated amenities where funding is available. • Residents/businesses can focus on plumbing protection (Toronto subsidies for backwater valves etc.) for the 35

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