Dramatic new commitments to water management are needed now.
Words by Michael Spaziani
If you’ve ever taken a bath, then you know all the basics of storm water management. (And if you’ve never taken a bath then I strongly suggest you do, then continue reading to learn a little more about this subject.)
Architects and urban designers are currently compelled to address storm water management in their designs for buildings, sites and communities. In most jurisdictions today, we must design our facilities so that the flow of water leaving a site does not exceed the rate of flow prior to development. So if you have an undeveloped site with post agricultural grasses and plants, your new development cannot release more water than established by that existing condition.
In other words: maintain the status quo.
As a result, you see new communities typically outfitted with new storm water ponds that collect and hold the rain water predicted for certain peak events such as a 100-year storm (that is, a storm of such severity that its probability of occurring is only once a century). The rain water carries along debris, salts, soil and silt as it scoots along off roofs, driveways, parking lots and roads into these ponds.
The ponds are typically designed with two basins: a settlement pond where silt and debris settles to the bottom, and a holding pond where the quantity of water is held and slowly released at a rate that prevents flooding.
Back to your bathtub. The source water is your faucet. The holding pond is your tub and the drain is the outlet back to the environment. Your tub will overflow when you forget to pull the drain plug or it gets plugged by hair and other debris or your water pressure is so high that the drain cannot release water quickly enough. What happens? You get a flooded bathroom.
That is what happened in Mississauga on July 8, 2013—too much source water and not enough outlet capacity. You saw the floods but you may have also had a wet basement caused simply by a careless neighbour draining a walkway onto your property. The heavy rain amplified the problem.
But why did this happen if the current standard is to hold all this water in storm ponds and release it slowly? The answer lies in the short history of Mississauga.
I contacted the Credit Valley Conservation Authority (CVCA), the stewards of our natural water systems. I conferred with Deputy Director John Kincaid and Senior Manager of Policy Christine Zimmer. They spoke passionately about their role in managing the evolving natural valley systems in light of both more frequent normal storm events (one in 10 years) and more peak events (one in 100 to 300 years) like we experienced with Hurricane Hazel and more recently on July 8.
I was shocked to hear this: only 25 percent of our land mass has water quantity controls in place. Conversely, 75 percent of our land mass lets water flow over it unstopped directly into our rivers and streams. When you consider the amount of hard surface built in Mississauga over the past 40 years, the resulting flooding is hardly surprising.
In the case of one-storey strip malls, you can usually expect 25 to 30 percent of a site to be occupied by roofs. You can also expect another 55 to 60 percent of the site to be covered with asphalt. That leaves 10 to 20 percent in landscape cover, which is mostly grass. If 75 percent of the strip malls out there have no quantity controls and 80 to 90 percent of each lot is covered by asphalt or buildings, you can imagine the huge flush of water released when a major storm passes through.
Add to this the flow from subdivision housing designed prior to 1985 and potentially built through 1995 (when approved plans didn’t require storm water quantity controls), and you begin to see the magnitude of the problem. Much of Mississauga’s housing was built in those dark ages prior to 1995. While the future is promising, the past is very disturbing.
I asked Ward 1 Councillor Jim Tovey about this immense problem. He added to my concern with the following tidbit: Mississauga needs $1.7 billion today to begin to solve this problem. That’s a crazy number that’s simply not available in the current economic climate. Mississauga is presently budgeting $10 million per year for erosion control and storm water management fixes. In 170 years we may have made a small dent in the problem. Wow!
And that only deals with the issue of quantity of water. There is the matter of water quality control that is perhaps even more dire. Prior to 1960, there were no controls at all on any new development. So a city like Toronto that is largely built well before 1960 has a huge problem. Salt, silt, sand and sometimes industrial waste finds its way into the sewers.
What can we do? CVCA has some great ideas. As our road systems constitute such a large impervious mass, they have conceived of a way to retrofit these public lands to capture water runoff, hold it and clean it prior to releasing it to our natural valley systems. A current project is the Elm Drive Showcasing Water Innovation retrofit in conjunction with the Peel School Board.
In this demonstration project, several techniques have been used to implement low-impact development protocols. They include parking laybys and sidewalks with permeable paving that lets water seep back slowly into the earth, and a series of rain gardens on school property that receive road runoff and filter it through their planter boxes prior to releasing it to the Cooksville Creek.
These innovations are a bright spot in an otherwise bleak situation. The sins of our fathers are now showing up as flooding and water pollution. The cost of fixing these sins is dear. How can we deal with it?
Kitchener and many American cities have developed a bold strategy that simply identifies the degree of storm water released from private development sites and creates a utility tax bill that builds targeted funds to allow public sector remedies to be instituted, such as the CVCA demonstration projects on public land.
In this program, the largest offenders are usually older strip retail malls that have little in the way of permeable surfaces and no storm retention ponds or other storage devices. Based on the amount of permeable surface or unrestrained runoff, a utility charge, much like your current sewer and water bill, is added to the worst offenders. As housing generally has about 50 percent of its lots in grass or other permeable surfaces, the majority of Mississauga homeowners would likely see no additional charge.
A taxation system such as this becomes a further incentive to redevelop these retail “greyfield” sites into new intensified developments that meet the current standards for storm water quality and quantity control. There are many new technologies that allow new developments to treat water onsite, recharge the ground water under them and maintain sustainable balanced conditions in our lakes and streams. New developments under new standards can do more to improve the environment than maintaining the harmful status quo. I believe most people believe the opposite.
So next time you take a bath, think about laying down some sod and wild flowers on the tub bottom, let it hold the water like a sponge, absorb the soap and dead skin cells, and then slowly release cleaner water back down the drain. At least think about it.
Michael Spaziani is an award-winning commercial architect and active community participant, serving on heritage and arts boards in Mississauga.
For more information on CVCA’s flood prevention projects, visit: creditvalleyca.ca/low-impact-development/showcasing-water-innovation-2/.