City of Edmonton officials released details Monday of a major plan to reduce the risk of damage to basements, vehicles and other property caused by rare flooding events.
The $2.6-billion proposal would protect neighbourhoods from a one-in-100-years storm.
“What we’re seeing and witnessing is more intense and frequency of those than we have in the past decades,” Todd Wyman, director in sustainable development, said. “This observed change in weather patterns is what we’re referring to now as our new normal.”
Edmonton’s pre-1960s drainage system has been evolving and severe weather events have led to upgrades in affected areas, including the addition of stormwater ponds in Mill Woods.
A recent report identifies high-level risk mitigation and investment scenarios affecting 160 older residential neighbourhoods.
“In mature neighbourhoods, they have a drainage route that goes to a pond, over land. We’re trying to recreate that in the established neighbourhoods. It’s a bit harder because you’re working with existing infrastructure and houses. But the standards, we’re trying to be the same.”
In July 2016, a massive downpour overwhelmed drainage systems and caused flooding in south Edmonton on Whitemud Drive, stranding drivers.
Flooding occurs when parts of Edmonton are hit with an unusually large volume of water in a very short amount of time.
In 2004, a severe storm flooded about 4,000 homes. In 2012, 1,200 residential properties were damaged by flooding from a storm. Improvements to drainage like stormwater ponds reduced basement flooding during later storms, the report found.
In 2013, the city started an Edmonton-wide, risk-based study for areas without major stormwater management systems. It looked at options to mitigate flood damage in over 160 residential and 33 industrial neighbourhoods.
City officials looked at four options to upgrade infrastructure to reduce flooding events — ranging between $2.2 billion to $4.7 billion — and suggested Scenario 3: “The New Normal,” which would handle a storm larger than a typical weather event.
“What you have to imagine is we’re opening up the front street of a neighbourhood to do improvements to that street. So, that deals with people in front of their houses and it does take some time.”
The “new standard,” Wyman said, would be able to handle those two massive storms Edmonton saw in 2004 and 2012.
These upgrades would take between 22 and 45 years to build. Over 45 years, it would mean $60 million is spent on the projects each year, without any help from federal or provincial grants.
“When we did some preliminary look through grants, there’s nothing that’s distinctly earmarked at this stage that we’re aware of,” Wyman said. “They’re also very sporadic. We would want to work with our other levels of government to ensure that we can apply grants where they’re available.”
If Edmonton doesn’t make drainage improvements, storms will continue to cause damage and things could get even worse, Wyman said.
“If nothing happens, the risk remains the same or gets worse. So there is a potential for what we’ve witnessed to date to continue to happen.
“What we’re saying is, it’s not actually the right design standard. We’ve seen the changes in the weather patterns, we’ve measured it. We’re suggesting the right standard would be a storm under Scenario No. 3 and that would be broadcast citywide so that everything can be brought up to the same standard over time,” Wyman said.
The report will head to committee on Friday for debate. Councillors will look at how the plan could impact utility rates. They’re also scheduled to talk about protecting parts of Whitemud Drive and Yellowhead Trial.
“We’ve seen the signs go out and the information go out on the Whitemud, and I believe the Yellowhead stuff is going to happen soon,” Wyman said.
“While we work with that and create the awareness, we’ll also want to help see how that’s working… and then understand what we can implement in the short term for some of those areas that maybe have a harder fix or a harder solution or there’s not a work-around or drive-around scenario.”
— With files from Scott Johnston, 630 CHED