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Don River Flooding

hawc

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I've lived in Toronto for over 40 years and the constant flooding we get around the lower Don River after a big thunderstorm is a relatively recent phenomenon.

Why is this? Does the river need to be dredged? Is there a blockage somewhere? Why is nobody on top of this?
 
Probably also have something to do with increased storm sewer outflows as more and more land in the watershed got built up as well.

AoD
 
No I don't think that's it. The land in the Don Watershed hasn't seen massive amounts of new development. It's all relatively mature development. It's something else.
 
Or maybe we had heavier storms that before? I think the dredging is ongoing, at least in the Keating Channel. It would be interesting to see a city report on this.

AoD
 
In the last 3-5 years, we have had much more intense storms than in the past. Keep in mind that lake water levels have also been increasing the last few years after reaching record lows several years ago. Sounds like we are just having a few wet years compared to past years.
 
Rainwater has a hard time to get filtered or adsorbed into the ground when there is asphalt parking lots, driveways, & roads, as well as large roofs. Both divert the rainwater, not into the ground, but into either storm sewers or the lowest area in the ground, which are the rivers, streams, and gullies.

These parking lot has a lot of surface area that adds the rainwater to flow off to flood.

parking_lot_001.jpg
parking-booth.jpg
 
We've also re-routed a lot of downspouts from the water treatment sewers to the ground.

Easiest fix for this is to re-route the Don so that it doesn't need to make the momentum/capacity stealing 90 degree turn at the lake.
 
It might be too soon to tell if this is a real pattern but it is no false observation that over the last number of years the frequency and severity of extreme weather events has increased and put greater strain on our infrastructure. That includes these fast torrential downpours that overwhelm the cities sewer systems. I personally have seen sewer back-up and flooding occurring in areas of the city that have not experience this in at least 35 years.
 
Flooding on the streets means that the sewers are at capacity. It also allows the rainwater to accumulate on the streets, creating temporary ponds until the sewers can take the runoff. The problem is with homes that are not sloped uphill enough that the backup may raise up higher and higher into basement windows.

No problem with street flooding.
steep-driveway_p1773982.jpg


May have a problem with street flooding.
blog-sloped-drive31.jpg


The city no longer likes having basement garages that require a sloping driveway going down to it. I'll bet there are homeowners who will try to dig out an illegal slopping driveway for their makeshift basement garage, but only without a permit.
 
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The city no longer likes having basement garages that require a sloping driveway going down to it.

I didn't realize there was a policy about them but it's probably for the best. They're also a pain in winter if your car gets stuck.
 
Reverse slope driveways are prohibited as per City of Toronto by-law.

The only way to build one is by applying for an exemption and getting a variance. For a residential attached or detached, I highly doubt you would receive such a variance without a lot of difficulty. Another part of the problem is that getting such a variance usually requires an assessment and approval from Toronto Water, who require that you have a P.Eng create a stormwater management plan for your property.
 
Reverse slope driveways are prohibited as per City of Toronto by-law.

The only way to build one is by applying for an exemption and getting a variance. For a residential attached or detached, I highly doubt you would receive such a variance without a lot of difficulty. Another part of the problem is that getting such a variance usually requires an assessment and approval from Toronto Water, who require that you have a P.Eng create a stormwater management plan for your property.

There are still a number of older sloping driveways in East York, but no new ones. I believe this is the reason you now see lots of new infill with the 'main floor' actually not at grade, with an attached at-grade garage with a level driveway in East York. Very car-centric suburban -- the idea of not having a car/garage is definitely not part of the culture. Amazing the number of hairy eyeballs I got riding the bus in a suit!
 

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