Flash flood at home in Ontario: what to do

Why they happen here

Severe summer thunderstorms can drop a month’s rain on part of southern Ontario in a couple of hours. Storm sewers are built for ordinary storms. When rain falls faster than drains, creeks and the ground can take it, water runs down streets, pools in low areas and underpasses, fills window wells and comes up through basement drains. Paved-over cities flood fastest. Toronto, Mississauga, Burlington, Hamilton and Windsor have all had damaging urban floods in recent years.

When a warning is issued

Environment and Climate Change Canada issues rainfall and severe thunderstorm warnings. Conservation authorities issue flood watches and warnings for their watersheds. If heavy rain is forecast:

• Clear leaves and debris from the catch basin outside your home, if it is safe
• Check that downspouts are attached and extended away from the house
• Clear window wells
• Test the sump pump and its backup
• Move valuables, electronics and documents off the basement floor
• Move vehicles out of low-lying spots and underground garages if there is time
• Charge phones

During the storm

Stay out of the water. A few centimetres of moving water can knock a person over, and less than half a metre can float a car. Flood water hides open manholes and debris, and it is contaminated with sewage.

Do not go into a flooding basement. Water that reaches outlets, appliances, the furnace or the panel can electrocute. Stay upstairs.

Do not try to save belongings from rising water.

Shut off electricity only if you can reach the panel while standing somewhere dry. If the panel is in the flooding area, leave it. Call your electricity distributor to disconnect.

Do not use the plumbing if drains are backing up. Avoid flushing and running water.

Do not drive through flooded roads or underpasses. Turn round.

Leave if you are told to, or if water is rising towards the main floor. Take medication, identification, phones and pets.

Call 911 if anyone is in danger.

When the water stops rising

Before you go into the basement

• Electricity. If water reached outlets, the furnace, the water heater or the panel, the power to the basement must be off before you step into the water. If you are unsure, wait for your electricity distributor or a licensed electrical contractor.
• Gas. If you smell gas, leave and call your gas utility from outside.
• Structure. Deep water puts great pressure on foundation walls. Look for new cracks, bowing or shifted walls before entering.
• Protection. Waterproof boots, gloves, eye protection and, for cleanup, a respirator rated for fine particles.

Do not pump too fast

If the basement is full or nearly so, pump it down gradually, in stages over a day or more. When the ground outside is saturated, the water inside is helping to resist the pressure on the walls. Emptying the basement quickly can crack or collapse them.

Record and report

• Photograph and video every room before moving anything, including a shot showing the water line on the wall
• Call your insurer or broker
• Report the flooding to your municipality. Most ask residents to do so, and the reports guide future drainage work.
• List damaged belongings

Find out how the water got in

It matters for the cleanup and for the insurance.

• Up through the floor drain, toilet or shower: sewer backup
• Through window wells, doors or over the foundation: overland water
• Through cracks and the floor joint: ground water
• Sump pit overflowing: pump failure or power cut

Often it is more than one.

Cleanup

Flood water from a storm is treated as grossly contaminated, whichever way it came in.

• Keep children, pets and anyone with a weakened immune system out
• Remove standing water
• Shovel out mud and silt before it dries
• Remove and discard carpet, underpad, upholstered furniture, mattresses, cardboard and other porous items that were soaked
• Cut out drywall and insulation to above the water line. Water wicks upwards inside the wall.
• Remove baseboards, panelling and laminate flooring
• Wash hard surfaces with detergent, then disinfect, then dry
• Run dehumidifiers and air movers until the structure reads dry
• Throw out any food, medicine and cosmetics the water touched, and anything in a fridge or freezer that warmed up

The furnace, water heater, washer, dryer and electrical panel must be checked by licensed technicians before they are used again. Appliances with flooded motors, controls or insulation often need replacing.

Start within a day or two. After that, mold sets in. See what to do when your basement floods.

Insurance

• Sewer backup needs the sewer backup endorsement.
• Overland water needs the overland water endorsement, which is not available at every address.
• Ground water seepage is often excluded.
• Standard policies without these endorsements generally do not cover flood water, though vehicles are covered under comprehensive auto insurance if you carry it.
• Additional living expenses apply where a covered loss makes the home unfit to live in.

After a major flood, the province may activate the Disaster Recovery Assistance for Ontarians program for a defined area. It helps with essential costs that insurance does not cover, within limits, and does not replace insurance. Check the Ontario government’s announcements.

Reducing the risk next time

• Backwater valve on the sewer connection
• Sump pump with a battery backup and an alarm
• Downspouts disconnected from the sewer and extended away from the house
• Ground sloped away from the foundation
• Window well covers and working drains
• Reverse-slope driveways need a working drain at the bottom and are a known weak point
• Valuables stored off the basement floor, in plastic bins
• Basement finishes that tolerate water
• A check with your broker that your water coverages match your risk

Many Ontario municipalities subsidise some of this work. See preventing basement flooding in Ontario.

More: basement flood cleanup.