How to prepare homes for extreme flooding events

As evacuation orders remain for hundreds of properties in southwest B.C., following catastrophic flooding that swept away houses and caused a municipality's wastewater system to fail — forcing its 7,000 residents to flee — experts say it's more important than ever to make homes flood resilient.

This means exploring ways to mitigate property damage and better protect flood-vulnerable spaces in homes.

What does this look like for individuals and communities? 

Experts offer some advice.

First: Find out if you live in a floodplain

Tamsin Lyle, engineer with floodwater management company Ebbwater Consulting, says it's important for residents to know about floodplains and whether their house is situated on one.

Lyle advises residents to check for water bodies surrounding their home, to note changes in rivers, including their water volume, and to speak to neighbours about flooding history.

While residents can ask local authorities for an up-to-date map of their area, these maps were developed 20 to 30 years ago and could use some improvements, Lyle adds.

"They were developed in a time with different information, different tools, and certainly not explicit about climate change," she said.

In an email, the B.C. Ministry of Forests said the province is currently updating provincial floodplain mapping standards and assessing potential gaps in existing coverage, which will help provide more information on high flood risk areas province-wide.

It's also important to find out if a house sits on land that had been reclaimed from bodies of water, says Deborah Harford, co-founder and senior advisor to Simon Fraser University's Action on Climate Team (ACT).

For example, Sumas Lake was drained in the 1920s to form a fertile hub of agricultural land that would be protected by dikes, canals and the Barrowtown Pump Station. But this infrastructure can get overwhelmed, prompting flooding concerns as dikes break.

Knowing more about the land on which their property sits can help residents prepare for the consequences of potential floods.

Keep water from flowing in with dry floodproofing

Dry floodproofing refers to construction measures that prevent or limit water from entering a building.

This includes putting up protective gates, like Dam Easy flood gates, and inflatable dams, also known as tiger dams, like the Aquadam previously installed in Kelowna.

Aluminum flood barriers, which range from 50 cm in height up to around six feet, are another temporary solution that individuals can purchase or communities can pitch in for, says Dirk Stroda, who owns Flood Control Canada, which sells temporary and permanent flood protective equipment.

Stroda also notes that while these solutions can help protect homes, it's still important to assess flood risk with municipalities to find the most appropriate solutions.

Design for water to flow out with wet floodproofing

For homes that are highly vulnerable to floods, wet floodproofing involves incorporating openings, such as flood vents, to a building, so that water can be removed with minimal damage.

This makes "[floods] relatively easy to clean up, but there won't be structural damage or expensive repairs required," says Steve Litke, a senior manager with the Fraser Basin Council.

For areas in the home that are likely to flood, residents can also consider using materials that are more resistant to water, such as water-resistant drywall, ceramic tiles, and waterproof concrete flooring instead of hardwood.

Place valuables on higher ground

When it comes to items inside the home, Lyle of Ebbwater Consulting says it's important to place valuables on higher floors rather than in basements.

Some new homes are designed with this in mind. In Cresent Beach, Surrey, for example, a September report to council notes that newer homes are being designed with ground floor levels used only for parking, foregoing storage space, electrical wiring or plumbing on the same floor. Habitable areas with more valuable belongings, such as technology and appliances, are being placed on higher floors.

New condos in Vancouver's False Creek neighbourhood are also being built with habitable spaces higher up, according to Litke of the Fraser Basin Council. The area, previously a large tidal mudflat, is especially vulnerable to flooding, with sea level expected to rise by one metre by the year 2100.

Community discussion is key

While there are many ways to make our homes flood resilient, cities need far more discussion with their communities about what equitable and flood resilient housing can look like, says Harford of Simon Fraser University's Adaptation to Climate Change Team. 

"Does it want to see innovative porous shorelines where you can let the water in?" she said.

"Are we willing to totally transform neighbourhoods so that they look different? ... Are we willing to move out of some areas?"

As climate change brings more challenges, she says it's key to consider flexible innovation for new construction and retrofits.

"The infrastructure of today was built for the world of yesterday. And it's not going to be adequate for the world that's coming in."