Photo: Nature offers the best defence against flooding

(Credit: Kurt Bauschardt via Flickr)

By David Suzuki with contributions from David Suzuki Foundation Senior Communications Specialist Theresa Beer.

Spring flooding in Canada this year upended lives, inundated city streets and swamped houses, prompting calls for sandbags, seawalls and dikes to save communities. Ontario and Quebec's April rainfall was double the 30-year average. Thousands of homes in 130 Quebec municipalities stretching from the Ontario border to the Gaspé Peninsula flooded in May. Montreal residents raced to protect their homes and families as three dikes gave way and the city declared a state of emergency. The Ontario government had to boost its resources for an emergency flood response.

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In Atlantic Canada, some parts of New Brunswick recorded more than 150 millimetres of rain during a nearly 36-hour, non-stop downpour. In B.C.'s Okanagan, rapidly melting snowpack and swelling creeks caused lake levels to rise to record heights. The City of West Kelowna declared a state of emergency and evacuated homes.

Floods have become one of the most visible signs of the effects of climate change in cities, towns and rural areas throughout Canada.

Spring floods aren't unusual, but the intensity and frequency of recent rains are breaking records. The Intergovernmental Panel on Climate Change, the leading international body for climate change assessment, anticipates a significant increase in heavy precipitation events and flooding in many parts of the world, including Canada. When temperatures rise, the atmosphere carries more moisture so when it rains, it dumps. The Insurance Bureau of Canada found one in five Canadians faces some level of flood risk, and 1.8 million households are at very high risk.

Climate change-related events — including floods, drought and fires — are a drain on personal finances and the economy. With more than 80 significant floods in Canada since 2000, insurance costs are skyrocketing. The 2013 Alberta floods alone cost more than $6 billion. Canadians personally shoulder about $600 million each year in losses related to flooding. Around the world, insurers have paid out more than $200 billion over the past decade in claims for damages caused by coastal floods.

Deforestation, wetland destruction and artificial shoreline projects worsen the problem. Insurance agencies recognize that, compared to expensive infrastructure, keeping ecosystems healthy prevents climate disasters, saves money and improves resiliency. Lloyd's of London encourages insurers to consider the value of natural coastal habitats when pricing flood risk. One study found ecosystems such as wetlands are more effective than seawalls in protecting against coastal storms. Insurers say conserving nature is about 30 times cheaper than building seawalls.

Still, many jurisdictions focus on engineered structures such as rock walls or even giant sea gates for coastal flooding, dams and levees to hold back rivers, and draining to prevent wetlands from overflowing. But built infrastructure costs cash-strapped municipalities money, requires more maintenance and is less flexible than keeping natural areas intact.

Urban concrete and asphalt surfaces prevent water from infiltrating into the ground and increase storm-water runoff. Rain gardens, bioswales and permeable pavements better manage flooding by reducing runoff and protecting flood plains and foreshore areas. Nature absorbs rainfall and prevents excess water from overwhelming pipe networks, backing up sewers and pooling in streets and basements. Restored river channels, parkways and beaches reduce costs, add valued amenities, increase access to nature and improve community health.

Many local governments are trying to keep up by limiting development in flood zones, better managing flood plains and updating flood-management systems. Some, such as Gibsons, B.C., are using a new approach that considers nature as a vital part of the town's infrastructure and puts "natural capital" assets on equal footing with built assets. The Municipal Natural Assets Initiative helps local governments across Canada test this approach by giving them tools to identify and account for community natural assets and improve management.

The federal government has set aside $2 billion to help local governments defend against natural disasters like fire and flooding. It should allocate a significant portion to natural infrastructure solutions. This would create the foundation for a national study of how much natural infrastructure contributes to biodiversity conservation, economic productivity and climate change mitigation and adaptation.

Despite recent investments, Canada lags behind other G7 nations in flood preparation and climate change adaptation. It's time we recognized the importance of intact nature and built green infrastructure as central to flood-prevention efforts. Nature can help us — if we let it.

June 29, 2017
http://www.davidsuzuki.org/blogs/science-matters/2017/06/nature-offers-the-best-defence-against-flooding/

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2 Comments

Sep 17, 2017
12:58 PM

The statement “Rain gardens, bioswales and permeable pavements better manage flooding by reducing runoff and protecting flood plains and foreshore areas. Nature absorbs rainfall and prevents excess water from overwhelming pipe networks, backing up sewers and pooling in streets and basements.” and that this approach reduces costs should be qualified. No Municipal Class Environmental Assessment study have identified these green infrastructure, low impact development measures as technically or cost-effective solutions to urban flooding (see all the recent Toronto Class EA consultation on slideshare, e.g., for Ares 40, 39, 38… or flood mitigation studies in Barrie, Waterloo, etc.) — the key driver for sewer back-ups is inflow and infiltration in partially separated sewer systems: https://www.iclr.org/images/BarbaraRobinsonSeptember152017.pdf LID infiltration will aggravate flooding by increasing extraneous flow in these constrained sanitary sewer systems. Also green infrastructure is more expensive than proven traditional engineering methods — LIDs cost $400,000 per hectare of drainage area to build and there are over 800,00 hectares of untreated urban land in Ontario — do the math and you see a cost of over $300B, excluding operations and maintenance and lifecycle replacement costs. This is a breakdown of the costs for Ontario cities: http://www.cityfloodmap.com/2017/03/expensive-green-infrastructure.html There is a role for green infrastructure, but it has to be strategic and should not inadvertently make flooding worse (by infiltrating runoff into already leaky sewer trenches and partially separated service areas … e.g., many parts of Canadian cities built before the 1980’s).

Jun 30, 2017
5:03 AM

Effects of climate change can be devastating. Let us resolve to manage our environment for prosperity.

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