The July 8 rainstorm — the most expensive in the province's history — pounded the western half of Toronto more than it did eastern parts, including Scarborough.

Ontario’s most expensive natural disaster barely felt in Scarborough

July storm prompts upgrades to sewer systems across the city

Toronto’s record-breaking summer rainstorm — the most expensive natural disaster in Ontario history, according to the Insurance Bureau of Canada (IBC) — left Scarborough relatively unscathed.

The insured cost of the July 8 storm was about $850 million in the GTA based on data the IBC received from Property Claims Services, an authority on insured property losses.

The storm brought with it record rainfall of almost 140 millimetres in just a few hours that “led to a power outage affecting at least 300,000 residents in Canada’s largest city, shut down subways, and left approximately 1,400 passengers stranded for hours on a commuter train filled with water”, the IBC said in a media release.

Toronto Water received over 4,700 calls regarding basement flooding, but only 50 came in from Scarborough, said Ted Bowering, director of water infrastructure management for Toronto Water.

“In Scarborough in fact the storm wasn’t all that intense. It was kind of like a normal summer thunderstorm,” he said. “So the impact was not that great at all.”

How to protect your home from basement flooding:

  • Mandatory Downspout Disconnection Program: Instead of having the water from downspouts flow straight in to the sewer, this by-law instead means water flows overland to a street catch basin or into a grassy area. When too much water goes directly in to the sewer than the sewer can handle, that’s when it starts backing up, causing basement flooding.
  • Add a backwater valve to your sanitary sewer line. This way, if the sewer water should ever back up, the valve would prevent if from coming into your house.
  • Connect weeping tile or foundation drains to a sump pump. By disconnecting them from the sewer system and attaching them to a sump pump, water collecting around the foundation of your house will be pumped to the surface. The City of Toronto offers a subsidy of up to $3,200 to ease the cost of installation of backwater valves and sump pumps.

—Source: Ted Bowering, Toronto Water

The total cost represents the damage to homes and vehicles in the GTA, said Pete Karageorgos, manager of consumer and industry relations for the IBC, which does “not have a breakdown by municipality or area.”

Toronto Water conducts environmental assessments that include studying the whole sewer and storm drain system to identify areas that need to be changed or upgraded through the capital budget process, Bowering said.

When Toronto Water was asked by city council for a report on what it planned to do following the storm on July 8, Bowering said his department recommended studying the entire city rather than the 34 previously identified basement flooding study areas.

“Our earlier program was that parts of the city are more at risk than others,” Bowering said. “What we found out was that all of the parts of the city are in about the same amount of risk, it just depends where it rains the hardest.

“The report shows a bunch of different storms and how the flooding complaints varied in the city depending on where the rain fell. So that’s what we’ve learned: we really need to look at the entire city.”

Beginning with areas affected by a storm in August 2005, Bowering said the city has budgeted about “10 years in the future, about $900 million” to do any needed upgrades.

This map shows the 34 Basement Flooding Study Areas identified by the city.
This map shows the 34 Basement Flooding Study Areas identified by the city. (Courtesy of the City of Toronto)