This article was originally published in the Burlington Gazette.
It’s disturbing when I see some people who keep repeating that climate change does not matter in our latest storm events. They really don’t know what they are talking about. The science matters, so bring it to the table.
Ontario is currently experiencing significant increases in stream and urban flooding thanks to climate change and inadequate provincial action, especially when these and other watershed-level impacts from climate change have been well known for years, and facts show that the Ontario government has known about and virtually ignored these issues for 25 years!
Most recent projections show Ontario warming is in the range of 3 to 5 C warmer in the mid-2000s than in the 1971 – 1990 period. Rain events are likely to become more intense, and we should prepare for greater variability of climate and occasional flood years.
Canadian models suggest that return periods will be halved; i.e a 20 year storm will become a 10 year event. We can expect longer, more drought events, punctuated by La Nina wet weather conditions sometimes leading to flooding. We are right in the later part of that warming period, and the predicted weather is just what we have been experiencing now.
The province has not updated their storm water design standards for 25 years. Further, they now appear to be backtracking, to support their housing growth plan, by not recognizing the reality that climate change weather is here. The City and residents have been getting financially soaked.
Recently, OLT Hearings at Millcroft have learned that those developer planners do not have to design storm water design systems for the real climate flood risk world, but only for what the province will allow them, which are the old guidelines.
We have been in a steadily warming state, and you cannot separate climate change, which is the new reality of the Earth, from how we choose to interact with how it affects us.
The recent peak rainfall rate and duration was far in excess of the design storm average rainfall rate peak and duration. July 15 reported 50 mm in 1 hour, and 65 to 80 mm in only 3 hours, with much more later on July 15 into July 16.
In the recent Gazette 4 part series, Mr. Barker points to record rainfalls at Pearson and Mississauga – of almost 100 mm on July 16 and 122.9 on July 15.
If the 100 year event from Hurricane Hazel in 1954, that too many here use to wrongly excuse climate change as not bad enough, is 200 mm in 24 hours, this recent 3 hour storm intensity is far in excess – 6.6 times – of any practical design capacity.
The flooding consequences and the locations, raise questions about the adequacy of in place excess volume and discharge controls, to see how the design storm water management actually constructed reduced the peak runoff, and lengthened the time of concentration, to an adequate design to reduce the post development runoff conditions to the pre development levels.
As a specific location of flooding consequences, the 407 is a location with a physical construct and urban context particularly at risk of extreme flooding events, such as this one.
More generally, the City is intent on rapid development in many places, building high density, with an intensification commitment to a large number of high rise condos and other housing forms. Storm water drivers include: the development catchment imperviousness; development driven increase in impervious surface; natural retention loss; and groundwater level impacts.
Concerns of Council, and the City as a whole, are the very large cost of getting the risk and flood damage costs in control. The Provincial control standards are not adequate and need updating and changing.
Since the July storm extremes are attributed to climate change, and are a signature event of such, of note that the atmosphere can hold 8% more moisture for every 1 degree C increase in temperature. The City says it is an emergency, but I see nothing in effective policy to seriously face this.
So to get to my point here, was the 407 storm water management designed and constructed adequately to control the July 15/16 storm intensity, duration, and amount featured by the direct rainfall onto the 407 large highly impervious catchment surface of asphalt and concrete with (runoff coefficients (85% – 95%), and steep soil side berm slopes (15-20%).
It is good engineering practice to modify these hydrology and hydrograph designs to adjust to deviations from typical rainfall excesses, intensities, duration, increase in percent of impervious surface, and other means. The City is entirely capable of doing all of this.
However, I get the impression that the City thinks it can’t afford to do it, and I see no visible efforts of the City to go after private owners, the 407, and the Province to fully scope the details of the inadequate state of their storm water design standards to get with the reality of climate.
Further, what is the City doing in general to face the reality of the storm water infrastructure, and existing combined sewers that contributed so much damage with this latest storm. And the need to review the general engineering practice – what is “standard practice”- and is it enough?
Given the accelerated development intensification plans in a climate change state, that just showed some small sample of what that means, this seems essential.
Somebody responsible needs to do this engineering and policy work.
