WC134 JanFeb 2024 - Magazine - Page 8
STORMWATER
Beyond Community Borders
Understanding flood risk means
looking well beyond the city limits
BY VINCENT CORMIER
It’s essential to collect
information about the study
area from all available
sources of information,
such as local testimonies,
reviewing aerial photos, and
contacting archiving centres.
LOOD MAPPING has become a popular practice for
helping communities understand how climatological events
impact municipal, commercial and residential assets. They
can help understand where the water might flow, the expected flood depths, and what might be at risk of being damaged,
or perhaps failing, in the wake of a severe weather event.
However, mapping the impact of floods and various hazards requires studying watersheds well beyond municipal borders to appreciate the true potential impact of climate events. What happened
in Calgary in 2013 is an excellent example of this, as the rainfall
and snowmelt that happened well beyond the city’s borders is what
caused the majority of the damage. Secondary structures, both
man-made and natural, have to be evaluated as part of the process.
But as our team learned first-hand while creating a flood inundation study for a city in British Columbia, there are more considerations, beyond the community borders, that must also be evaluated
to ensure that the community appreciates exactly what might
exacerbate the impact of a severe storm.
F
Evaluating the landscape
There are fundamental elements included in any flood assessment.
Using topographic and bathymetric data, a Digital Elevation Model
is generally created to allow for hydraulic modelling of various bodies of water located within the study area’s boundary. Some form of
hydrological analysis is then required to estimate the expected water
flow frequency and magnitude with a focus on potential climate
change impacts on flow regimes. Finally, a numerical hydraulic
model is built using the Digital Elevation Model and hydrological
inputs to calculate the potential water levels, depths and velocities
for present and future meteorological events.
In parallel, it’s essential to collect information about the study
area from all available sources of information, such as local
Vincent Cormier
Vincent Cormier is a hydrotechnical engineer, design
lead and project manager at WSP, with over 10 years
of experience in the fields of hydrotechnical design,
dam engineering and hydropower.
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WATER C AN ADA • JANUARY/ FEBRUARY 2024
