Climate Resiliency Strategy

The City undertook a Climate Vulnerability and Risk Assessment to identify the top climate risks facing Ottawa. This is the second phase of the Climate Resiliency Strategy development.

The Climate Vulnerability and Risk Assessment draws on the climate projections developed in 2020 as well as input and expertise from City staff, community partners and the public. It assessed how vulnerable Ottawa is to changing climate conditions and prioritizes where action is most needed.

The project assessed close to 150 potential climate impacts on health, community well-being, infrastructure, natural environment and the economy. Of these potential climate impacts, 40 priority risks were identified that require action in the next one to three years. These include risks related to higher temperatures and more precipitation, as well as more extreme weather like flooding, severe winds and freezing rain.

Some of the priority risks include, but are not limited to:

• Increased heat-related illnesses
• Increased need for cooling in buildings (especially in community buildings like schools, low-income housing and private long-term care facilities)
• More invasive species, pests and diseases harming trees, greenspaces, and agricultural production
• New or intensified disease vectors (for example ticks that carry Lyme disease, or mosquitoes that carry West Nile virus)
• Increased damage to roads, buildings and other infrastructure from freeze-thaw and freezing rain
• Flood damage to infrastructure and property from heavy rains and riverine flooding
• Increased pressures on the City and community services to respond to simultaneous or repeated extreme weather events
• Reduced access to essential services such as electricity, healthcare, education, food banks and transit during extreme weather
• Increased pressures on low-income and other disproportionately affected people (mental, physical and financial health)

More information about these climate impacts is available in the Climate Vulnerability and Risk Assessment report and Appendix D (Climate Vulnerabilities and Risks by Focus Area). A summary of the priority risks is also available.

The Climate Vulnerability and Risk Assessment was presented to the Standing Committee on Environmental Protection, Water and Waste Management on June 21, 2022 and City Council on July 6, 2022. You can watch the recordings of Committee and Council on YouTube.

Ottawa’s climate is already getting warmer. Between the mid-1940s and the mid-2010s the average temperature in Ottawa increased by 1.3 degrees Celsius.

This trend will continue in the future. Ottawa will be warmer year round, there will be more extreme heat days and less extreme cold days.

What we are expecting

By the 2050s, under a high-emission scenario, temperature in the National Capital Region is projected to change in the following ways.

• Increase in average temperatures in all seasons – the average temperature will increase by 3.2 degrees Celsius.
• Less cold extremes – the number of days below -10 degrees Celsius will decrease by 35 per cent. That’s a decrease to 46 days per year from the current 71 days.
• More warm extremes – there will be four times as many very hot days over 30 degrees Celsius. That’s an increase to 43 days per year from the current 11 days.
• Increase in humidex – the number of days with high humidex levels will increase.
• Drought – more variability in precipitation and risk of drought

You can find out more details of what to expect in the 2030s and 2080s in the Summary of the Future Climate in Canada’s Capital Region.

What are the top risks from extreme heat and drought?

• Increased heat-related illnesses – extreme heat can cause dehydration, heat exhaustion, heat stroke and even death.
• Less outdoor recreation and active transportation – hotter and more humid summers could lead to a decrease in outdoor recreation and sports and the cancellation of community events.
• Increased need for cooling in buildings – as temperatures rise, there will be more demand for cooling in the summer which will increase energy costs. Buildings may also need to be retrofitted to add better cooling and ventilation. Community buildings such as churches, daycares or schools may be forced to close temporarily during extreme heat events if they do not have adequate air conditioning.
• Increased demand for shaded areas and indoor and outdoor recreation facilities to offset heat
• Impacts on the natural environment – extreme heat and drought place additional stress on our ecosystems. Algal blooms are harmful to human health and will cause no swim advisories.
• Reduced agricultural yields and increased irrigation – extreme heat and drought create challenging growing conditions and reduce harvest.

More information about the climate impacts facing Ottawa is available in the Climate Vulnerability and Risk Assessment.

Who is most vulnerable to extreme heat?

High temperatures can put everyone at risk, especially those without access to air conditioning. Health risks are greatest for infants, older adults, people who work or exercise outdoors, those with pre-existing health conditions, and people experiencing homelessness.

Reduced access to recreation could impact the mental health and wellness of individuals and families who could find themselves even more isolated if free/low-cost outdoor activities are cancelled.

How can you prepare?

We all have a role to play in preparing for the impacts of changing weather patterns and extreme events. Find out what you can do, what the City is doing and visit the Resource Hub (coming soon) where we have additional resources that can help communities prepare for climate change.

The Urban Heat Island Effect

The urban heat island effect occurs when built-up areas are hotter than surrounding areas. Buildings, parking lots and other dark surfaces retain heat and become hotter than nearby greenspaces, water and rural areas. The annual mean air temperature of a city with one million people or more can be one to three degrees Celsius warmer than its surroundings during the day. In the evening, the difference can be as high as 12 degrees Celsius.

The City of Ottawa in partnership with Ottawa Public Health created two urban heat island maps using satellite imagery from July 18, 2019, a hot day where temperatures reached 27.3 degrees Celsius and the humidex reached 31:

• Map showing temperature differences for Ottawa
• Map showing temperature differences within Ottawa’s Greenbelt

The colour codes show how surface temperatures ranged from 15 to 38 degrees Celsius across the City. The map shows cooler areas include the Ottawa and Rideau Rivers and their tributaries; the Greenbelt; greenspaces, parks, natural spaces; and light-coloured surfaces including buildings with white roofs. Buildings with dark roofs, such as those found on large commercial and institutional buildings, parking lots and artificial turf show up as hotter areas that absorb and retain heat.

These maps highlight areas of potential additional risk created by the urban heat island effect. Additional factors that influence an individual’s risk include access to air conditioning at work, school, home and during commutes, if they work or exercise outdoors, their age, and pre-existing health conditions.

How are these Urban Heat Island Maps being used?

Heat island maps show us how land use choices affect surface temperature. With temperatures expected to rise by 3.2 degrees Celsius by the 2050s and the number of days above 30 degrees Celsius expected to rise fourfold to 43 days, heat islands worsen the impact of extreme heat events. Extreme heat affects everyone, but certain people are more vulnerable to heat stress, including the very young and old, people who are pregnant, people with existing health conditions, people who work outside, athletes, people who are homeless or precariously housed, and those that don’t have good access to air conditioning.

Heat island maps can be used to guide policies and planning of the built environment. Strategies to reduce surface temperatures include tree protection and plantings, the use of vegetation on and around buildings and parking lots, and the inclusion of parks and greenspace and reflective surfaces such as light-coloured roofs.

Average temperatures are increasing across all seasons causing their typical characteristics to change.

What we are expecting

By the 2050s, under a high-emission scenario, seasons in the National Capital Region are projected to change in the following ways.

• Earlier springs – the last day of spring frost will start two weeks earlier
• Later falls – the first day of fall frost will be three weeks later
• Shorter winters – winter will be shorter by five weeks
• Shift in freeze-thaw cycles – winter temperatures will hover around 0 degrees Celsius more frequently in the future. Winter freeze events will increase by 33 per cent
• Decrease in snowfall – the annual total snowfall will decrease by 20 per cent.
• Shorter snow season – the first snowfall will be later in the year, and the last snowfall will be earlier. As a result, the number of days with snow cover is projected to decrease from the current 115 days to 72.

You can find out more details of what to expect in the 2030s and 2080s in the Summary of the Future Climate in Canada’s Capital Region.

What are the top risks from changing seasons?

• More invasive species, pests and diseases harming our natural environment and agricultural areas
• Increase in cases of Lyme disease, West Nile virus and possibly other diseases as extended warmer seasons enable increased tick and mosquito populations. Other disease that are not currently prevalent in our region could also increase.
• Increased slips and falls in icy conditions from increased winter freeze-thaw.
• Damage to roads, buildings and other infrastructure from increased winter freeze-thaw and freezing rain, leading to more maintenance requirements and increased risk to users.
• More pressures on parks and beaches from increased use.
• Decline of winter tourism and recreation as less snow and warmer conditions mean reduced opportunities for activities such as skating, skiing and snowshoeing.

More information about the climate impacts facing Ottawa is available in the Climate Vulnerability and Risk Assessment.

Who is most vulnerable?

Warmer temperatures put everyone at risk. Outdoor workers and individuals that spend a significant time outdoors are at increased risk of Lyme disease and West Nile virus. Pedestrians are at increased risk of slips and falls due to increased icy conditions, and persons with limited mobility may be more isolated.

How can you prepare?

We all have a role to play in preparing for the impacts of changing weather patterns and extreme events. Find out what you can do, what the City is doing and visit the Resource Hub (coming soon) where we have additional resources that can help communities prepare for climate change.

Ottawa has seen increased rainfall over the past decades, especially in spring and fall. As our climate warms, these trends will continue. There will be an increase in both the amount and intensity of rain, including in winter months.

What we are expecting

By the 2050s, under a high-emission scenario, precipitation in the National Capital Region is projected to change in the following ways.

• Increase in total precipitation (except in summer) – the total amount of precipitation (rain and/or snow) will increase in spring, winter and fall by eight per cent. Rainfall in summer (June – September) will not increase.
• Wet days will be wetter – although the total annual precipitation will increase, this precipitation will be concentrated within the same number of ‘wet days’. The maximum amount of precipitation that falls in one day will increase by 15 per cent.
• Increase in freezing rain – the colder months will likely see more freezing rain due to the increase of days around zero degrees Celsius. Freezing rain in spring and fall will likely decrease.

You can find out more details of what to expect in the 2030s and 2080s in the Summary of the Future Climate in Canada’s Capital Region.

What are the top risks from more intense rainfall and flooding

• Flood damage – more intense rainfall can overwhelm sewer systems and increase the risk of flooding in our streets and homes. Riverine and inland flooding can damage or reduce access to roads, transit, pathways, property and other infrastructure. Increased precipitation can also damage and overwhelm stormwater, wastewater and flood protection infrastructure.
• Mental, physical and financial health – flooding negatively impacts the health of those directly affected. It can also cause mold and contaminate private wells and septic systems.
• Reduced agricultural yields – more variable rainfall and the risk of flooding create challenging growing conditions and reduce harvest.
• See additional risks from freezing rain in the extreme weather section below.

More information about the climate impacts facing Ottawa is available in the Climate Vulnerability and Risk Assessment.

Who is most vulnerable?

Some people are at higher risk from increased precipitation. Communities in flood-prone areas may be affected more frequently or severely making it more challenging to prepare and respond to flood events. Lower-income and other disproportionately affected households are particularly vulnerable. Communities that rely on private wells in flood prone areas are more at risk of contamination to their drinking water caused by flooding.

How can you prepare?

We all have a role to play in preparing for the impacts of changing weather patterns and extreme events. Find out what you can do, what the City is doing and visit the Resource Hub (coming soon) where we have additional resources that can help communities prepare for climate change.

Flood plain mapping and climate change

Flood plain mapping identifies the areas that may experience flooding due to rising water levels in a watercourse. An interactive flood plain map which uses flood hazard mapping produced by the local Conservation Authorities in partnership with the City is now available. The map shows three different flood events:

• A large flood event which has a 2 per cent chance of happening in any given year. Also known as a 1 in 50-year flood
• A regulatory flood event which has a 1 per cent chance of happening in any given year. Also known as a 1 in 100-year flood.
• A more extreme flood event that could occur with climate change. Also known as a 1 in 350-year flood.

The effect of climate change on the magnitude and probability of future flood events is difficult to predict. Local climate projections for the National Capital Region indicate trends of warmer temperatures, increased amounts of rain (including in the winter and spring), as well as more intense rainfall. This can all affect river levels and flows. The 1 in 350-year flood event was selected as an appropriate larger flood event for assessing potential changes in riverine flood hazards and risks due to climate change.

Purpose and use of flood plain mapping

Floodplain mapping is critical for the effective management of riverine flood risks through the prevention/mitigation of risks, protection of people and property, and emergency preparedness and response planning. Effective hazard and risk management will often involve a combination of measures. The City, Conservation Authorities, and property owners all have a role to play in flood risk management. As per the City’s Official Plan, for example, any new development in a 1 in 350-year flood area must demonstrate how it will mitigate the risks of more severe flooding.

How are these maps being used to inform the Climate Resiliency Strategy?

The 1 in 350-year flood hazard maps are being used to inform the development of the Climate Resiliency Strategy. The maps can be used to identify which communities, parks and infrastructure could be affected by more severe flooding. The information is being used, for example, to inform plans to ensure continued service at the City’s water purification plants and wastewater treatment plant.

Learn more about flood plain mapping

By 2050 there will be an increased likelihood of extreme weather events such as flooding, heat waves, ice storms and severe winds.

Ottawa’s weather is becoming more variable and unpredictable. In recent years we have experienced more extreme heat, wind, rain and winter storms. Some examples of extreme weather events in Ottawa include:

• Five successive ice storms in January 1998, which caused massive damage to trees and electrical infrastructure causing widespread power outages and a shutdown of activities across Ottawa and the region for several weeks. The storm is the second most expensive natural disaster in Canadian history with $2.3 billion in insurance payouts.
• Over 50 cm of snow in February 2016, which caused closures throughout the city and set a new record for the biggest snowfall in a single day
• Significant flooding along the Ottawa River in the spring of 2017 and 2019 resulted in extensive property damage and health concerns
• Tornadoes in 2018 and 2019 caused extensive damage to property and prolonged power outages.
• A prolonged extreme heat event that lasted six days in July 2018. On Canada Day, at the hottest time of the day, humidex levels made it feel like 47 degrees Celsius.
• The Ontario-Quebec derecho in May 2022 that killed 10 people, caused widespread property damage and left hundreds of thousands of people in Ottawa without power for several days. The storm is the sixth most expensive natural disaster in Canadian history.

What we are expecting

By the 2050s, under a high-emission scenario, we can expect:

• Favourable conditions for ice storms or severe snow storms, tornadoes and high wind gusts, droughts and wildfires
• Increase in freezing rain and ice storms – the colder months will likely see more freezing rain due to the increase of days around zero degrees Celsius.

You can find out more details of what to expect in the 2030s and 2080s in the Summary of the Future Climate in Canada’s Capital Region.

What are the top risks from an increase in extreme events?

• Increased winter maintenance of roads, sidewalks and pathways due to freeze-thaw cycles and freezing rain
• Increased risk of slips and falls and isolation due to icy sidewalks
• Reduced ability of City and community services to effectively respond to simultaneous or repeated extreme events
• Extended power outages when electrical infrastructure is damaged
• Reduced access to essential services such as healthcare, education, food banks and transit during extreme weather impacting residents

More information about the climate impacts facing Ottawa is available in the Climate Vulnerability and Risk Assessment.

Who is most vulnerable?

Extreme events put everyone at risk, but they disproportionally impact populations such as Indigenous Peoples, older adults, low income, homeless and racialized people. More remote rural populations may have reduced access to roads and utilities. Persons with disabilities or mobility issues may be homebound as they wait for snow and ice to be cleared. Those living in communities that have experienced past emergencies may also experience increased anxiety.

How can you prepare?

We all have a role to play in preparing for the impacts of changing weather patterns and extreme events. Find out what you can do, what the City is doing and visit the Resource Hub (coming soon) where we have additional resources that can help communities prepare for climate change.

Thank you to everyone who has provided input into the Climate Resiliency Strategy. We received over 500 responses to the surveys. A summary of responses can be found in the What We Heard Report. The key findings are summarized below. This is an updated version of the Interim What we Heard Report that was released in June, 2021.

Key findings from Ottawa residents, businesses, institutions and organizations:

• 92% of respondents are very concerned or concerned about climate change
• The top three concerns about climate change are:
  • The increase in the number of heatwaves and the number of hot days above 30 degrees Celsius (78%)
  • Changes in the natural environment (71%)
  • Increased risk of flooding (70%)
• The most common impacts experienced by respondents are heatwaves (77%), changes in the natural environment (50%) and high winds/tornadoes (49%)
• When asked to describe how they’ve been affected respondents told stories of their property, health, operations or lifestyles being impacted by extreme weather events (heatwaves, drought, flooding, tornadoes, ice storms), Lyme disease and increased winter temperatures
• Just over half (50%) say they are very prepared or somewhat prepared for the impacts of climate change. 31% say they are not prepared
• Taking steps to keep safe in the sun and keep homes cool were the most common actions that respondents are already taking followed by protecting against ticks and mosquitoes. Developing an emergency preparedness plan, checking in on neighbours during extreme heat events and protecting against ticks and mosquitoes were the most common actions that respondents are planning to do.

Input from the surveys was considered during the Climate Vulnerability and Risk Assessment and will be used to help inform the Climate Resiliency Strategy.

We look forward to hearing more from residents and stakeholders as we develop the Climate Resiliency Strategy. We encourage you to stay engaged and informed by:

• Signing up to the climate change e-newsletter
• Regularly checking this page for updates

The Climate Resiliency Strategy will review the impacts of climate change, assess where the City is vulnerable and prioritize solutions. The City has been addressing climate change risks for many years, including the following initiatives:

• An Emergency Management Plan to prepare and respond to the needs of the community during a major emergency such as flooding, while still ensuring continuation of essential services
• Environmental health education, awareness and response plans to reduce climate related illnesses and deaths associated with ultra violet radiation, extreme heat and humidity, cold weather, poor air quality (including wildfire smoke), flooding, Lyme disease and West Nile virus.
• Applying a climate and health lens to the new Official Plan (policies that guide the building of the city) and its supporting documents to build energy and climate resiliency into future growth and development. The new Official Plan integrates climate change mitigation and adaption policies throughout. For example, it includes revised policies to reduce the impacts of the urban heat island effect, reduce risks in areas vulnerable to flooding and protect our natural and agricultural areas.
• Raising awareness of the link between health and the built environment and highlighting how residents can get involved to make changes in their communities to become more resilient to climate change.
• Using urban heat island maps to better understand what areas are impacted by hot weather, and to inform policies that will reduce the urban heat island effects to better protect public health.
• Supporting community gardens to encourage local production of food
• Building our infrastructure to be resilient in future climate conditions such as extreme weather, greater rainfall and higher temperatures. For example:
  1. new City sewers are designed to handle larger rainfall events to reduce the risks of flooding.
  2. the City’s wastewater treatment plant is being upgraded to permit the plant to operate independent of the utility grid, using power produced on site to so it can remain operational in the event of a sustained power failure.
  3. using asphalt that is more resistant to temperature fluctuations for roads, pavement and parking lots
  4. the new Combined Sewage Storage Tunnel will greatly reduce the frequency of sewage overflows during storms from entering the Ottawa River and reduce the risk of basement flooding in downtown neighbourhoods.
  5. flood response plans are in place at the City’s two water purification plants to protect this critical infrastructure during a flooding event along the Ottawa River, in order to ensure continued drinking water supply
• Growing Ottawa’s urban forest and making it healthier, more diverse and resilient through the Urban Forest Management Plan.
• Supporting homeowners with grants for backwater valves through the Residential Protective Plumbing Program
• Supporting farmers to adopt new technologies that protect soils and enable them to manage variable rainfall events through the Rural Clean Water Program
• Promoting sustainability and building resiliency in the agriculture and agri-food industry through innovation and knowledge transfer at the Ottawa Smart Farm, which focuses on leveraging technology to help producers optimize their efforts and overcome challenges such as changes in growing seasons and extreme weather events.