Urban greening for climate resilience - Flooding

August 1, 2023

By Christine Desrochers

To address the ongoing climate crisis, the Government of Canada has released the National Adaptation Strategy and the Government of Canada Adaptation Action Plan. Nature-based solutions (NbS) play a key role in these plans.

This continuing blog series explores what NbS are and how they can help address climate change. Our first blog post explored how urban greening can reduce deadly extreme heat. Now we will discover how nature can help address the costliest disaster across Canada: flooding.

Rising floodwaters

Flooding is Canada’s most costly natural disaster, causing billions of dollars in damage to property and infrastructure every year.

Uninsured losses amount to about half of total flood damage costs, with residential property owners bearing approximately 75% of these uninsured losses. Home flood insurance is becoming increasingly expensive and difficult to obtain, however, putting homeowners at financial risk. About 10% of Canadian homes are in high-risk zones ineligible for flood insurance. Increasing climate-related floods would be devastating for many households across the country.

Floods can also take a harmful toll on human life and health. Risk of drowning and injury from floodwaters, washouts, and landslides are immediate concerns, but there is also risk of disease from contaminated water and mold growth. Long-term mental health impacts like anxiety, depression, and PTSD can also arise and last for years following a flood event.

Flooding can also compound other interrelated societal challenges. For instance, increasing flood risk, lack of home insurance, and devastating property damage may displace families and intensify the ongoing housing crisis. Like most climate-related impacts, flooding also worsens inequality by systematically impacting disadvantaged groups more severely.

Urban Flooding

Extreme weather events are predicted to worsen in cities as the climate crisis continues. Urban regions are particularly vulnerable since they have more paved areas and high-value property. Aging stormwater infrastructure can no longer keep up with the rapid development happening in many Canadian cities. To make matters worse, protective wetlands are being lost to urban sprawl and sea levels are rising.

It is clear that we need to take urgent preventative action to protect Canadians against increasing climate-related floods.

Nature offers a solution

Nature holds the key to resiliency. Natural systems like wetlands and forests absorb excess stormwater during heavy rainfall events, acting like a sponge.

We can work with nature to protect against worsening floods and take proactive steps in emergency preparedness. Nature-based solutions that reduce flooding can include constructed and restored wetlands, naturalized channels, green roofs, rain gardens, bioswales, street trees, and strategic land conservation. These engineered solutions can work in conjunction with traditional urban grey infrastructure, or even replace it.

Proactive investments in nature-based flood solutions are extremely cost-effective. For every $1 invested in adaptation, $6 is saved in disaster mitigation costs. In addition, NbS are up to 50% cheaper than traditional grey infrastructure.

There are many co-benefits of natural infrastructure that further support investment in these solutions. Our previous work outlines the holistic value of wetlands, urban forests, and green roofs as climate solutions. In addition to flood mitigation, their benefits include carbon sequestration, local cooling, increased biodiversity, clean water and air, and recreation opportunities. Increased access to nature also greatly improves human health and wellbeing – Canadian cities that expand urban parkland and tree canopies can realize millions of dollars in annual health cost savings.

Case Study

The Port Lands Flood Protection Project by Waterfront Toronto is a prime example of a major Canadian project that is applying NbS for urban flood protection. SPI had the opportunity to attend a tour of the construction site during the 2023 Park People Conference and learn first-hand from the project leaders.

The Port Lands site was created in the 1920’s by filling-in marshland around the mouth of the Don River for an industrial and shipping hub. The river valley is now being naturalized with completion scheduled for 2024. Wetlands and other natural and grey flood control features are being built alongside extensive parkland. This project will protect billions of dollars worth of property in downtown Toronto from flooding and create new lands for recreation and development.

Flood protection provided the business case for investment, but many high-value co-benefits will also be realized. The Port Lands project will remediate contaminated land and create habitat for fish, birds, and other wildlife. More parkland, greenspace, and waterfront access will improve recreation and health outcomes for residents and visitors. The project will also help address the region’s housing crisis by protecting existing homes and building new ones. A new mixed-use community will be created on the site and additional housing may be built upstream on lands previously within the floodplain.

The Port Lands project showcases the wide-ranging benefits of applying nature as a holistic solution to urban challenges.

Research in Action

Cities across the country should invest in NbS to reduce urban flooding and help Canadians adapt and thrive in a changing climate. Canada’s National Adaptation Strategy gives some direction and funding support, but urgent action is needed to implement NbS at a large scale. These solutions must be prioritized and their multiple benefits accounted for in decision making.

Smart Prosperity Institute enthusiastically supports the wide adoption of nature-based solutions, and strives to empower decision-makers to prioritize NbS by presenting the solid business case for investment. We look forward to continuing this timely and important work across Canada in the months and years ahead.

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