On May 31, 2019, ICLR conducted a Friday Forum webinar lead by Dr. Slobodan Simonovic of Western University titled 'Modelling of Future Flood Risk Across Canada Under Climate Change.' Climate change has induced changes in key climate variables and the hydrological cycle across Canada. With continuous emission of greenhouse gases, this trend is expected to continue over the 21st century and beyond. In this study, a macro-scaled hydrodynamic model is used to simulate 25 km resolution daily streamflow across Canada for historical (1961-2005) and future (2061-2100) timelines. Future projections from 21 GCMs following four Representative Concentration Pathways (RCPs) were used for the analysis. Changes in the frequency and magnitude of historical 100-year and 250-year return period flood events and month of occurrence of peak flow are analyzed. Results obtained from uncertainty analysis for both return period flood events found that flood frequency will increase in most of the northern Canada, southern Ontario, southern British Columbia, northern Alberta, Manitoba and Saskatchewan. However, northern British Columbia, northern Ontario, Manitoba and northeastern Quebec will be facing decrease in flood frequency. Results indicate that 40%-60% of Canada’s 100 most populated cities including many prominent cities such as Toronto and Montreal are high at risk of increased riverine flooding under climate change. Slobodan P. Simonovic is Professor of Civil and Environmental Engineering at the University of Western Ontario and Director of Engineering Studies at ICLR. Prof. Simonovic is globally recognized for his unique interdisciplinary research in Systems Analysis and has over 500 professional publications and three major textbooks. Prof. Simonovic was inducted to the Canadian Academy of Engineering in June of 2013.

1. Modelling Future Flood Risk Across
Canada Under Climate Change
Slobodan P. Simonović
FCAE, FCSCE, FASCE, FIWRA
Department of Civil and Environmental Engineering
Western University

2. INTRODUCTION2|
Funding
• NSERC CRD with Chaucer Synd.: 2015-2019 $1,375,600
Research team
• Prof. Slobodan P. SIMONOVIC
• Mrs. Ayushi GAUR
• Mr. Abhishek GAUR
Research support

3. CONCLUSIONS3|
• First Canada-wide assessment of future changes in flood
hazard and risk
• Comprehensive assessment of uncertainty by considering
large ensemble of future runoff projections
• Northern provinces of Canada, south-western Ontario, north-
eastern Quebec, and southern prairies are expected to face
increase in frequency of flooding
• Northern prairies and north-central Ontario will experience
decrease in frequency of flooding
• Larger parts of Canada are expected to experience earlier-
than-usual snowmelt driven floods
• Southern Ontario cities are associated with highest increases
in future flood risk
• Flood characteristics will change at majority of the flow
regulation locations highlighting the importance of revising
long-term regulatory rules to adopt to changing conditions

4. INTRODUCTION4|
• Introduction
• Research objectives
• Methodology
• Models and data used
• Analysis and results
• Conclusions
Overview

5. INTRODUCTION5| Canada – observed climate change

6. INTRODUCTION6| Canada – climate model predictions

7. INTRODUCTION7| Flood modelling
• Flow on floodplains is
controlled by topography
and friction
• Complex spatial patterns of
water depth and velocity
(2D in space and dynamic in
time)
• Large scale modelling
possible
• Simplified 2D hydraulic
models
• Faster computers

8. RESEARCH OBJECTIVES8|
• Investigate changes in the frequency and magnitude of
100-year and 250-year return period flood events across
Canada;
• Investigate changes timing of peak flood events across
Canada;
• Assess the future flood risk to Canadian cities and flow
regulation infrastructure
• Assess the uncertainty introduced by multiple GCMs and
emission scenarios in projecting future changes in flood
frequency and magnitude

9. METHODOLOGY9| Flood modelling

10. METHODOLOGY10|Runoff projections

11. METHODOLOGY11|Flood modelling – CaMa-Flood model
• CaMa-Flood (Catchment-based Macro-scale
Floodplain) global hydrodynamic model (University
of Tokyo)
• Grid –based river and floodplain routing
calculations
• Input - runoff forcing from land surface schemes
within GCMs
• Flow calculation in each grid (specific unit-
catchment)
• Output - water storage
• Flexible Location of Waterways ( FLOW ) method
– Up-scaled river network map preparation
– Sub-grid characteristics (channel length, channel altitude,
distance to downstream, unit-catchment area and flood
elevation profile)
• River network map is prepared tracing the fine
resolution flow direction map.

12. MODELS AND DATA12|Data sources
• Daily historical and future GCM runoff data: Daily runoff
data for historical (1961-2005) and future (2061-2100)
timelines collected for future emission scenarios.
• Historical reanalysis flow data: Daily NARR reanalysis
flow data obtained for the duration 1993-2007.
• Daily historical river discharge data from HYDAT: Daily
river discharge data collected for RHBN stations located
in Canada for the duration 1993-2007.
• Population data: Population data for 100 most populous
cities of Canada obtained from Statistics Canada (2017)
for the year 2015.

13. ANALYSES AND RESULTS13|Flood simulations
• Continuous daily simulation of historical (1961-2005)
and future flow projections (2061-2100) across Canada
• Input daily flow data obtained from 21 Global Climate
Models taking all available emission scenarios (84 future
and 21 historical runs)
• Change in 100-year and 250-year return period flood
magnitude estimated
• Flood frequency analysis is performed by fitting the
annual maximum flows using Generalized Extreme Value
(GEV) distribution
– Scale, shape and location parameters estimated
using method of moments

14. ANALYSES AND RESULTS14|Computational challenges
• Challenge - to perform flow and flood inundation calculations at
over 1 million model grids located in Canada, and for over 3
million days including different climate models, emission
scenarios, and time-periods.
• Solution - SHARCNET computations utilizing 24 cores on one node
of “copper” system.
– Installation of WinSCP and PuTTY.exe programs on local machine.
– Specify paths to gcc and ifort compilers on SHARCNET in the MKinclude file
of CamaFlood model.
– Specify appropriate simulation settings in the model including the number
of cores for parallel computations.
– Submit job to run CamaFlood model on SHARCNET using following sqsub
command:
sqsub –q threaded –n 24 –r 4h –mpp=16g –o outputfile.txt global_15min.sh
– Copy outputs from SHARCNET to local machine for post-processing.

15. ANALYSES AND RESULTS - FREQUENCY15|Single model results - 100-year: BCC-CSM-1-1

16. ANALYSES AND RESULTS - FREQUENCY16|Aggregated median results - 100-year

17. ANALYSES AND RESULTS - FREQUENCY17|Robust median results - 100-year

18. ANALYSES AND RESULTS - FREQUENCY18|Uncertainty analyses

19. ANALYSES AND RESULTS - TIMING19|Robust median – 100 year

20. ANALYSES AND RESULTS - TIMING20|Robust median – 100 year

21. ANALYSES AND RESULTS - RISK21|100 most populated cities – 1072 FRI locations

22. ANALYSES AND RESULTS - RISK22|100 most populated cities – 100 year flood RCP 8.5

23. ANALYSES AND RESULTS - RISK23|Selected cities – robust median
• 40%-60% of Canada’s 100 most populated cities are high at
risk of increased riverine flooding under climate change.
City RCP 2.6 RCP 4.5 RCP 6.0 RCP 8.5
100 year 250 year 100 year 250 year 100 year 250 year 100 year 250 year
Toronto 22 37 32 46 32 39 15 23
Montreal 26 38 22 32 18 25 11 16
Edmonton 104 >500 200 >500 200 >500 284 104
Hamilton 37 56 151 78 200 67 27 56
Winnipeg 198 >500 200 >500 200 >500 200 >500
Kitchener 26 47 200 86 200 57 29 60
Pierrefonds district of Montreal, May 2017 Pierrefonds district of Montreal, May 2019

24. ANALYSES AND RESULTS - RISK24|1072 flow regulation infrastructure locations – 100 year flood
• 45%-60% expected to
experience increases in
flood magnitudes
• 25%-60% expected to
experience changes in flood
timing

25. CONCLUSIONS25|
• First Canada-wide assessment of future changes in flood
hazard and risk
• Comprehensive assessment of uncertainty by considering
large ensemble of future runoff projections
• Northern provinces of Canada, south-western Ontario, north-
eastern Quebec, and southern prairies are expected to face
increase in frequency of flooding
• Northern prairies and north-central Ontario will experience
decrease in frequency of flooding
• Larger parts of Canada are expected to experience earlier-
than-usual snowmelt driven floods
• Southern Ontario cities are associated with highest increases
in future flood risk
• Flood characteristics will change at majority of the flow
regulation locations highlighting the importance of revising
long-term regulatory rules to adopt to changing conditions

26. RESOURCES26|
• Gaur, A., A. Gaur and S. P. Simonovic (2017). Modelling of High Resolution Flow
from GCM Simulated Runoff using a Mesoscale Hydrodynamic Model: CAMA-
FLOOD. Water Resources Research Report no. 101, Facility for Intelligent
Decision Support, Department of Civil and Environmental Engineering, London,
Ontario, Canada, 44 pages. ISBN: (print) 978-0-7714-3154-8; (online) 978-0-
7714-3155-5.
• Gaur, A., A. Gaur, and S.P. Simonovic, (2018) “Future changes in flood hazard
across Canada under changing climate”, Water, Feature Paper, Special Issue
Extreme Floods and Droughts under Future Climate Scenarios ,10(1441):21,
open access, PDF Version: http://www.mdpi.com/2073-4441/10/10/1441/pdf
• Gaur, A. Gaur, A. and S.P. Simonovic (2019) “Modelling of Future Flood Risk
Across Canada Under Climate Change”, WIT Transactions on Engineering
Sciences, 121:149-161, available online: https://www.witpress.com/elibrary/wit-
transactions-on-engineering-sciences/121/36682
• Gaur, A., A. Gaur, and S.P. Simonovic, (2019) “Future changes in the hazard and
risk of flooding in Canada’s most populated cities and flow regulation
infrastructure”, Water, Feature Paper, Special Issue on Extreme Floods and
Droughts under Future Climate Scenarios: 11(1), 63; doi:10.3390/w11010063.,
open access http://www.mdpi.com/2073-4441/11/1/63/pdf

27. THANK YOU27|
QUESTIONS
www.slobodansimonovic.com