By Tom Muir
August 25th, 2024
BURLINGTON, ON
OPINION
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.
Flood water streaming from the Cavendish Road community down onto the 407 highway.
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.
The Ontario Land Tribunal (OLT) hearings on the Millcroft golf course development made clear – 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 a recent Gazette four part series, David Barker points to record rainfalls at Pearson and Mississauga – of almost 100 mm on July 16 and 122.9 on July 15.
Toronto Star report on the damage and loss of life from Hurricane Hazel in 1954
If the 100 year Hurricane Hazel (1954) event, that too many use to wrongly excuse climate change as not bad enough, is 200 mm in 24 hours, this recent three 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 on the part 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.
Is this enough?
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.
Tom Muir is an Aldershot resident and former federal government researcher..
Dee, that is simply not correct. I would reference you to the report by Cumming Cockburn, November 2000. “Hurricane Hazel and Extreme Rainfall In Southern Ontario. Note Table 4 on Page 12 that shows the Design Recurrence interval, use of Hazel for Major Drainage Systems at a recurrence of 100 years, and in fact lists Burlington as on the Municipalities in the Study Area!
https://www.iclr.org/wp-content/uploads/PDFS/hurricane-hazel-and-extreme-rainfall-in-southern-ontario.pdf
Note this report was published 24 years ago, and note the near misses of large storms reported even back then.
Hurricane Hazel, the regulation storm, is considered a 400 to 500 year storm, actually. It is not the 100 year storm.
Being one of the readers who have commented in the past on this topic, and specifically pointed to the event of Hurricane Hazel in 1954 as a bench mark used in engineering for the design of storm water management systems. I will qualify, that at the time as a consulting engineer I worked as project manager on such projects but did not complete the calculations myself, but had specialist engineers review methodology and calculations with me. My expertise specifically is in the area of wastewater, drinking water and industrial water reuse.
As the province reviews policy on this, I would note that changes in policy and design standards only affect new systems and typically not existing.
Modelling of storm water is not a precise calculation and involves many variables. Yes the average daily precipitation of a 1 in 100 year event is taken into the calculation, but as we all know intensity varies over the course of a day, so designers apply instantons factors account for this, so to say what we saw in July over a 3 hour period and then compare it to an average of 200 mm in 24 hours is a bit misleading.
Designers also have to consider saturation of permeable ground prior to storm events, this is art as much as science. Different soil types and geological conditions have different drainage characteristics adding to the complexity.
Modelling flow in open channels, culverts and ditches also has its own level of complexity and call it imprecisions, especially if the design dimensions change over time due to debris, growth and infill.
As a result of these and other assumptions/decisions that have to be made in designing systems in the real world, engineers also apply safety factors. Simply speaking systems are made 10% to 50% larger to account for uncertainties in the real world.
As a society, we can make such systems larger, change design standards etc, but this also involves a economic calculation of risk. How much money is put in to a system to make it larger, what is the present worth of the money over time and what is the cost when the system is exceeded. Someone has to pick of these costs, it’s generally the tax payer and there is not a limitless supply of tax payer money. Then compare this to all the other issues in our society that need tax dollars.
I’ve been advocating a step back, what is the city’s design standard and what are we doing to maintain our systems at that design standard. The design standard includes precipitation for sure, but also must include various design safety factors.
I would guess this in some 100 plus page report, unfortunately I’ve yet to find it.
Excellent points.
Thank you to both Michael and Tom for your respective research and information on this subject. If City staff responsible for water management would only meet with you two and agree to an action plan for at least the continuous maintenance to design standards Michael refers to (whatever they are and wherever they are found at City Hall) then that would at least be a start and a concrete (pun intended) beginning to separate all the talk of what went wrong again this time from actual real physical work at sites to clean up all of the watercourses in Burlington. That is the priority right now.
As long as the Province continues to support the Ivory Courtroom that is the OLT, cities and citizens have no choice but to recover from its willfully foolish decisions – after the fact, and at great expense.
Tom is getting carried away! First… there are no known combined sewers in Burlington. Secondly… the storm design standards are reviewed and updated regularly.
Editor’s note: We have asked Muir to respond to this comment.
Doug, if there are no combined sewers in Burlington, why were there public complaints from residents of sewage backups in basements, and so much debate about the need for, and efficacy of, sewage backup valve installations by residents? Can you provide some insight into this matter?
This factual history in the public debate from flood-affected residents, was not me getting carried away, and was the unspoken basis for the evidence I used that some storm – sanitary connection was going on. The City could have reported on this to residents, but I did not see any of this. Do you have anything to say on this?
Likewise, from my experience, it is you getting carried away with your claims that storm design standards are updated regularly. With this claim, you imply that these updates are implemented, and that makes any difference with the entire existing City infrastructure from the past, as Michael above says.
In the latest City storm of July15/16, the staff stated publicly that the storm was caused by climate change, and the City used “Standard Procedures”, without stating what that was. It was not climate change deviated procedures, and it was not adequate.
Otherwise, with the province taking over all planning and development power, it is OLT that determines what standards have to be met by applicants, and there still are no deviations for climate change that I know of for to “Standard Procedures”. This means that moving forward all development at OLT will be governed by Provincial policies.
Regarding Provincial policy in this regard, as I noted, it 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.
For a lot of information on this matter, used in my Opinion.
https://ontarioheadwaters.ca/climate-change-and-watershed-management-2/
https://ontarioheadwaters.ca/wp-content/uploads/2024/08/TRCA-1999-Climate-Change-and-Watershed-Management.pdf
Thanks for this Tom. Now we need to put our heads together to determine who will ensure we have the correct storm water and sewage infrastructure is in place to prevent. It certainly did not happen after 2014 and from what we heard at the OLT we will be facing the same situation on a repetitive basis.
Excellent points Tom and very well made.
Great article – the Province appears to be turning a blind eye here for the purposes of enabling development as detailed in the Auditor General’s report of 2022. The four ministries identified in the report are Ministry of Housing, Ministry of Infrastructure, Ministry of Environment and Ministry of Natural Resources. There are many instances where provincial projects on this topic were shelved perhaps because they didn’t suit the Premier’s focus.
This week at the Association of Municipalities of Ontario Conference, the Ministry of Housing committed to a new Provincial Policy Statement and stated that Municipalities “know best where to build houses”. Yet the City of Burlington unanimously opposed development on the golf course and has put forward two resolutions to the Province requesting that they intervene to stop the development, one of which was supported by the Region. Still, the Ontario Land Tribunal, an agency of the government with its appointments, decided (as they do in 97% of cases) to enable the development. If it is true that municipalities know best, then the Province should intervene and stop development when the City requests it and also, the Province should abolish the OLT.