Wetlands and Flood Mitigation in
Ontario:
Natural Adaptation to a Changing Climate
Owen Steele
Head Conservation Programs
Ducks Unlimited Canada, Ontario
Ducks Unlimited Canada
Our MISSION:
DUC conserves, manages and restores wetlands and
associated habitats for North America’s waterfowl.
These habitats also benefit other wildlife and
people.
Our WORK:
DUC has been working with landowners,
governments, and other organizations since
1938 to preserve over 6.4 million acres of
wetland and associated habitat in Canada.
Our GOAL in Ontario: 1) Reverse wetland loss
and achieve a net gain in wetlands; 2) Promote
significant investment in wetlands as natural
green infrastructure.
Wetlands as Green Infrastructure
• Wetlands are highly productive ecosystems
that provide benefits to wildlife and society:
– Water filtration
– Carbon sequestration
– Erosion control
– Drought prevention
– Flood attenuation
Extreme Weather in Ontario
• Extreme weather, flooding on the rise in southern
Ontario due to climate change
• Increasing costs for government, businesses and
homeowners
• Need for innovative
solutions to manage
water in a changing
climate
Wetland Flood Storage
Project Purpose
• Assumption that wetlands help control
flooding…
– …but how effective are they? How much can they
reduce flooding? Where do they limit flooding the
most? And what is the economic value?
Research will help answer these questions and
determine the role and value of wetlands in
southern Ontario
Project Overview
Phase 1
Literature Review
• Objective 1
• Review scientific
literature related to
wetland flood
attenuation.
• Complete a gap
analysis.
• Create a literature
review document.
Phase 3
Phase 2
Hydrologic Modelling
• Objective 1 & 2
• Determine
landscape based
wetland
characteristics and
functions that
influence
downstream flood
depth
Hydrologic / Economic
Interface
• Organization of key
hydrological outputs
that impacts
economic
considerations
• Flood depths and
duration by a range
of flood return
periods
• Understanding of
wetlands influence
flood depths for
each assess return
period
Economic Assessment
• Objective 3
• Estimate the avoided
damage costs
associated with each
modeled flood
return period
Develop Business Case
• Objective 4
• Utilize information
to develop a
business case for
wetland protection
and restoration
Literature Review
Balance of academic literature confirms that wetlands
can help mitigate flooding:
• Wetland drainage in the Canadian Prairies has led to an increase of
up to 350% in flood peak flow (Pomeroy et al, 2014)
• A 1 acre wetland that is 1 foot deep can hold 330,000 US gallons of
water (Hallock et al, 2015)
• A 5.7 acre wetland can retain the
natural runoff from a 410 acre
watershed (Godschalk et al, 1999)
Literature Review
Estimates of the economic value of flood mitigation
provided by wetlands include:
• $380 million per year in the Greenbelt (Wilson 2008)
• $157 million per year in the Lake Simcoe Watershed (Wilson 2008)
• $16 million per year in the Credit River Watershed (Kennedy and
Wilson 2009)
Credit River Watershed
Modelling Status
• Oak Ridges Moraine Hydrogeology Program
• Built using HydroGeoSphere
– Integrated GW/SW model
– Fully-distributed
• Storm events characterized (2, 5, 10, 25, 50, 100, Ontario record
year returns)
• Wetland scenarios developed
• Uncertainty analysis at SciNet HPC
Modelling Scenarios
All 7 scenarios will be modelled under 7 rainfall intensities (2yr, 5yr, 10yr, 25yr,
50yr, 100yr, Ontario’s record maximum)
1. A baseline scenario using existing wetland extent
Wetland Restoration Scenario:
2. Loss of all geographically isolated/Headwater wetlands
3. Loss of all riparian/riverine/lowland/floodplain wetlands
4. Loss of all Non-Provincially Significant Wetlands (PSWs)
5. Projected near-term loss using CVC Natural Heritage System
4. 100 % Wetland Loss
Wetland Restoration Scenario:
7. Restored wetlands at all CVC planned restoration sites
Summer 2015 Convective Storm Event
Baseline scenario using existing wetland extent
Hydrologic Model/Economic Interface
Phase 2
Hydrologic Modelling
• Objective 1 & 2
• Determine
landscape based
wetland
characteristics and
functions that
influence
downstream flood
depth
Phase 3
Hydrologic / Economic
Interface
• Organization of key
hydrological
outputs that
impacts economic
considerations
• Flood depths and
duration by a range
of flood return
periods
• Understanding of
wetlands influence
flood depths for
each assess return
period
Economic Assessment
• Objective 3
• Estimate the
avoided damage
costs associated
with each modeled
flood return period
Develop Business Case
• Objective 4
• Utilize information
to develop a
business case for
wetland protection
and restoration
Hydrologic/Economic Interface
To ensure success of the economic analysis and the development of a business case, it is essential for the hydrological
model outputs to be key inputs into the economic analysis. The following provides an initial scoping of key outputs
required to inform the economic damage assessment:

For each flood return period, a range hydrologic outputs that characterize the flood events, including:
o Overland flood depths
o Overland flood velocity
o Overland flood duration
o The spatial extent of flooding
Economic Assessment
Phase 3
Economic Assessment
•Objective 3
•Estimate the avoided
damage costs associated
with each modelled flood
scenario
Develop Business Case
•Objective 4
•Utilize information to
develop a business case for
wetland protection and
restoration
Conceptual Potential Outcomes
Overarching Goals
• Understand wetland value as natural green
infrastructure assets
• Wetland conservation (protection, restoration and
management) becomes part of climate change
adaptation and storm water management planning in
Ontario communities
• Municipalities, CAs and others are equipped with the
necessary tools to implement conservation actions
Stay tuned…