Robert Muir Extreme Rainfall Trends - NRC Workshop on urban rural s...

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Woodbine
1
Workshop on adaptation to climate change impact on
Urban / rural storm flooding
February 27, 2018
National, reg...

Woodbine
Outline
2
• Environment and Climate Change Canada (ECCC) Engineering
Climate Datasets (version 2.3)
– Annual Maxi...

National Annual Maximum Rainfall Trends Data
• ECCC added trend analysis in
the v2.3 Engineering Climate
Dataset, showing ...

Very Few Significant Trends in Canada (random)
• 93% of trends are not
significant or ‘no data’.
• 5-min rainfall maxima
h...

5http://www.cityfloodmap.com/2015/12/canadian-extreme-rainfall-map-climate.htmlhttp://www.cityfloodmap.com/2015/12/canadia...

National Data Trends Contradict Media & Marketing
• Insurance ‘facts’ & infographics
refuted by ECCC as inadequate
for dec...

Mixing-up Annual Precip. Data and Extreme Rainfall Risks
“Indeed in Canada, in southern Canada we are getting about 18% mo...

Less Extreme Short Duration Rain - Southern Ontario
• 97 % of trends not statistically significant (mild trends up & down)...

No Change in Annual Maxima = No Change in Derived IDF
• Southern Ontario 21
stations with 30+ years
of record have median
...

No Change in Annual Maxima = No Change in Derived IDF
• Southern Ontario 21
stations with 30+ years
of record have median
...

Local Trend - Lower 5-Minute IDF For 2 to 100 Year
• Toronto Downtown
and Mississauga
Airport 5-15 min.
intensities decrea...

Southern Ontario Extreme Rain Trends Decreasing
http://www.cityfloodmap.com/2017/11/less-extreme-short-duration-rainfall-i...

100-Year 15-Minute
Future IDF
Uncertainty
• Various options:
– Tool / Method
– Station / Cell
– RCP/ Conf.
Bands
– Timefra...

100-Year 15-Minute
Future IDF
Uncertainty
• Various options:
– Tool / Method
– Station / Cell
– RCP/ Conf.
Bands
– Timefra...

100-Year 2-Hour
Future IDF
Uncertainty
• Various options:
– Tool / Method
– Station / Cell
– RCP/ Conf.
Bands
– Timeframe
...

100-Year 24-Hour
Future IDF
Uncertainty
• Various options:
– Tool / Method
– Station / Cell
– RCP/ Conf.
Bands
– Timeframe...

Is IDF data
critical to
design?
Does it
account for
real system
stresses?
18

Is IDF data
critical to
design?
Does it
account for
real system
stresses?
19

IDF data is
just the “tail
on the dog”
... don’t let
“the tail wag
the dog”
when
defining risk
20

IDF Data Use (To Create Hyetograph) is Most Critical to Risk
• Regulatory floodplain hyetographs can underestimate 100-yea...

Hyetograph Selection Effects Major Runoff Peaks (Storm)
• Various 100-year storms to assess peak flows in Toronto InfoWork...

Hyetograph Selection Effects Surcharge (Sanitary)
• Several wastewater design storms were used to assess surcharged manhol...

Hyetographs & Hydrology have safety
factors to account for complex reality
• Chicago storm: “the synthetic storm pattern w...

Conclusions
• Newest ECCC Engineering Climate Datasets Version 2.3 trends and
significance for each station/duration defin...

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