How to Prevent Basement Flooding During Heavy Rain

Mobilizing Alberta is an initiative aimed at increasing engagement on climate change across Southern Alberta. Through Climate Action Grants, a Climate Conversation Speaker Series, and the Preparing Albertans for Climate Change e-course, Mobilizing Alberta provides a foundation on which Albertans can build awareness and support meaningful climate action. Over the next few months, we’ll share a series of informative blog posts to answer frequently asked questions, clear up common misconceptions, and break down climate solutions in a straightforward, easy-to-understand way.

Basement flooding is a growing risk as Alberta faces more rainstorms intensified by climate change. Learn how to prevent water damage during heavy rain with practical, climate-smart upgrades for your home.

According to the Insurance Bureau of Canada, flooding caused over $40 million in damage in 2023. Climate change, caused by burning fossil fuels, is changing our weather patterns. Our “weird weather” occurs because the extraction and burning of fossil fuels creates greenhouse gas emissions that act like a warming blanket, which leads to more frequent extreme weather events, like floods.

Depending on the rate of greenhouse gas emissions, Alberta’s temperature is predicted to rise by 2.0°C by the 2030s and 4.0°C by the 2060s (compared to the 1990s). This will mean less predictable weather, with higher levels of annual precipitation (but a decline in precipitation in the summers) and the greater chance of extreme weather events, like floods.

If the rainfall in the summers is decreasing, how does that make us more vulnerable to floods? Even if total numbers are lower, extreme rainfall — which dumps large volumes of water in a short period of time — often causes flash flooding. In urban areas, streets can become impromptu rivers as stormwater systems struggle to keep up with the volume of water. Outside of cities, areas like the front ranges of the Rockies have very little soil to absorb water, so heavy rainfall flows straight downhill. In areas struck by drought, the land is too dry to absorb all the water at once, and if the region is recovering from wildfire, the sudden moisture may result in mudslides.

Wherever it occurs, flooding is disruptive, devastating, and potentially deadly. It destroys homes, businesses and infrastructure, causes economic upheaval, and can ruin livelihoods. As Albertans face the risk of increased floods, we need to be aware of how to protect our homes, ourselves, and our communities.

There are small things you can do around your house to help ensure you’re less likely to flood — or, if you do experience a flood, to mitigate the impact. Some of these things are cheap fixes or ongoing seasonal jobs that keep your home in good repair, and can help you avoid much larger repair jobs (cracks in foundations, for example). If you rent, you can take care of some of these suggestions while others would require sharing this information with your landlord.

• Keep moisture away from your foundation. Clear snow away, and make sure water drains away from your house. The grade of your yard should slope away from your home (so water will drain away from the foundation). You may need to regrade your property if water pools anywhere or drains towards your home.
• Fill in any cracks or holes in your foundation or concrete around your home, and make sure your weeping tile is draining properly (look for standing water or damp ground around the exterior, or a musty smell in the basement).
• Check weather stripping on windows and doors and re-seal as necessary.
• Keep drainage pipes, eavestroughs, and storm drains clean and clear of any debris. Make sure downspouts and drainage pipes drain more than three meters away from your foundation.
• Apply sealant to exterior features to help waterproof them.
• Clean out your window wells.
• Be careful what you store in the basement—try to keep everything up higher and packed in sealable plastic containers.
• If you have windows at or near ground level, install window wells with a rock layer for drainage three to six inches below the bottom of the window. Use transparent window well covers to help prevent water and snow from piling up in the window well, but still let light into the basement.
• Install a water alarm to quickly alert you to the presence of water. 
• Use rain barrels to help collect water—this is also great for conserving water. You can use the water you collect for your plants.
• Install backflow valves to prevent sewer backup damage.
• Install a sump pump. We recommend having a backup generator or battery in the event the power goes out. Note: Many cities have bylaws against allowing water to drain directly onto neighbouring properties, lanes, sidewalks, boulevards, streets, or into a foundation drain or weeping tile.
• If your property has a sump pump, it’s the homeowners' responsibility to maintain it. Basement seepage due to a sump pump malfunction is also the homeowners' responsibility.
• Proper landscaping with plants can prevent soil erosion and help soak up water.
• Have sandbags ready to go if there’s a high flood risk (Acera insurance).

If your basement floods, your first priority should be to make sure you’re safe. Start by checking with your municipality and local providers to see if power, gas, water and sewage services are working. Make sure drinking water is safe, and there are no boil-water advisories (see the next steps and resources section below).

• If there’s water above any of the electrical outlets, baseboard heaters, or your furnace, or it’s near your electrical panel, leave the house and confirm the power is off. Electricity can move through water or wet flooring and deliver a serious electrical shock.
• The safety devices installed in natural gas appliances and equipment can be affected by flooding and may not work properly. If your house has flooded and any of your natural gas appliances (including furnaces, boilers, water heaters and dryers) have come into contact with water, they’re not safe to use.
• Before you use any of your utilities, including furnaces, water heaters, appliances and electrical equipment, get a certified technician to examine them. Make sure everything is dry before you plug appliances in again.
• Wear protective clothing, like disposable overalls, protective eyewear, gloves and a face mask before checking items that have been submerged in floodwater.
• Make sure the area is well ventilated — open windows if you can, or use fans to help things dry.

If you need to pump water out of your basement, you may want to hire a professional who can do it safely. If you’re handing it yourself, find out before you start if your municipality has any restrictions and where you should pump the floodwater.

• Drain the water in stages. The Government of Alberta recommends draining about one-third each day. If the ground around your house is still saturated and you remove the water too quickly, the walls or floors could buckle.
• Use equipment safely and choose the right pump for your conditions. Gas-powered pumps must be used outdoors as they can be deadly thanks to carbon monoxide.

Once the water’s removed and it’s safe for you to be in the flood zone, you need to deal with the belongings left behind as soon as possible. The more quickly you can remove items, the more quickly you can avoid rot, mildew, mold and warping.

Your insurance company may help with some of these tasks, such as determining what can be salvaged or what needs to be disposed of, and finding a service to professionally clean and dry some items (such as carpets and furniture).

• Keep a list of what you remove and organize it according to whether it can be salvaged or discarded.You’ll likely need to make a few trips to the dump to dispose of some items — other, smaller items may be fine to put in your bin for regular collection.
• Any flooring that can absorb moisture — including wood flooring, underlayers and carpet — needs to be removed and likely discarded.
• Completely dry and disinfect the foundation, floor, walls, furnace and any other fixed features or objects that have had contact with floodwater.
• Use old rags and towels, or a wet-dry vacuum, to remove excess water.
• Use a mild bleach solution to sanitize surfaces, including ceilings. To make a bleach solution, mix one tablespoon of bleach with four litres of water.

Alberta Health Services offers a comprehensive resource to help you clean house after a flood.

To learn more about how to make sure you’re prepared in case of a flood, check out the following resources:

• Follow local media, local municipalities, and Alberta Emergency Alerts for updates and advisories.
• Download the Alberta Emergency Alert app to help you stay aware of emergencies and evacuations.
• Consider other climate-ready home upgrades to prepare your home.