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.

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. OUTLINE
•Lost Rivers and Urban Flooding
•Ward 13 and 14 Flood Risks
•Extreme Rainfall Trends – Media
Myths
•Urbanization & Intensification
Stresses
2

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. 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. TORONTO

6. Valleys &
Flood
Hazards

7. Overland Flow
beyond the
Valleys

8. Even More
Overland
Flow

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. Wards 13
& 14

11. Regulated
Valley
Features

12. Overland
Flow Paths

13. Overland
Flow Spread
(Estimated)

14. Flood Reports
Ward 13 & 14
(approx.)

15. Flood Reports
Other Areas
(higher risks)

16. Wendigo Creek
Spring Creek

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. Environment and Climate Change
Canada Refutation of Claim:
18

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. • 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. • 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. 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. 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. We’ve seen this before…
24http://www.cityfloodmap.com/2017/05/go-train-flooded-in-1981-too-media.html
=

25. 25
25

26. SO WHAT IS CAUSING
MORE FLOODING?
•Urbanization and intensification
•Only Milli Vanilli
Blame it on the Rain
26

27. 50 YEARS OF URBANIZATION
27

28. Urban ‘Pink Splat’… like Cat in the Hat
… don’t think we’ll get
old hydrology back. 28

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. WHAT IS INCREASING RIVER
FLOW ?
•University of Guelph research says
urbanization and not changing climate
30

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. 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. 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. reen Infrastructure
Cost for 1050 ha =
$420,000,000
1050 hectares

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