City of Toronto Overland Flow Map - 100-Year Storm Major Drainage System Spread & TRCA Watershed Major Drainage Centreline

CityFloodMap.Com presented GIS-based, hydrologic and hydraulic overland flow analysis over the past couple years (the "2015" Toronto overland flow analysis and spatial analysis correlating overland flood limits to reported basement flooding in 2000,2005 and 2013, and then the "2016" southern Ontario-wide analysis that includes refined hydrologic parameters). This provides an important insight into urban flood risk management and the influence of surface flooding on sanitary/wastewater system inflows (e.g,. via doors, windows, walk-outs, depressed driveways) - the extraneous flows that particularly stress partially separated sanitary systems, causes sewer surcharge and basement sewage back-up.

Here is the analysis clipped to the City of Toronto including the estimated 100 year flow spread and a 2x 100-year flow spread. The also includes overland flow paths within Toronto (the centreline of the major drainage flow path) and outside of Toronto covering the entire TRCA watershed areas ((c) CityFloodMap.Com):

The major drainage system flow spread in Toronto is essentially a buffer from this centreline considering each reaches hydrology (rational method) and hydraulics (standard road cross section assumed, but overland flow segment defines longitudinal average slope (or a minimum to avoid zero's for segments across filled sinks that have no slope). As a bonus, geotagged social media is embedded in the ArcGIS Online map - generally this is useless using the search term 'flood' to filter images but there is the odd correlation of overland flow path with real flooding pictures. The map is interactive - you can zoom in and even search for an address - enjoy! Hopefully the social media Flickr and Twitter images become more relevant and abundant over time. If you want to see a clean version without social media, scroll to the bottom of the page. More details on the analysis including the basement flooding correlation is described here:


Urban Flood Risk from Flood Plains to Floor Drains from Robert Muir

An example geotagged surface flooding picture that corresponds to the mapped overland flow path:


The map below is cleaner, excluding social media geotagged 'flood' images, and showing only City of Toronto 100-year overland flow spread and flow path centreline in TRCA watersheds ((c) CityFloodMap.Com). Note, approximate TRCA regulation boundaries are estimated from camaps.ca georeferenced image feature, and shoreline/slope regulation areas have been excluded to focus more on where river flood risks exist:

Book Review: The Rightful Place of Science: Disasters & Climate Change - Ontario Cities Flooding Perspective

Roger Pielke, Jr.'s 2014 book  The Rightful Place of Science: Disasters & Climate Change is a must-read for anyone interested in understanding and mitigating flood damages in Ontario cities. It reinforces several local themes presented in this blog as well, e.g., extreme rainfall is not increasing (due to climate change or anything else), flood damages are influenced by other factors and are not increasing as a result of more frequent of extreme rainfall.

Pielke has been recently highlighted in the Wall Street Journal where he shares his "Unhappy Life as a Climate Heretic".

Hurricanes

Pielke demonstrates that the frequency and severity or strength of hurricanes (tropical cyclones) has not increased over the past century. This is good news for Ontario where many river flood hazards are defined by Hurricane Hazel as the regional storm regulatory event in many Conservation Authority jurisdictions.

He also delves into damages resulting from these events, normalized to reflect the increase in the number of people and the amount of property in vulnerable areas. While losses have increased it is due to the increase in assets at risk - the normalized damages are in fact 'flat'.

In Ontario, the percentage of properties lie in river flood plains where hazards are governed by hurricane events is in the very low single digits. Nonetheless, decreasing hurricane frequency is a good thing.

Extreme Precipitation

Citing IPCC, Pielke notes that there have been statistically significant decreases and increases in 'heavy precipitation' events, and that there are strong regional and subregional variations in the trends. It is important to note the definition of heavy precipitation is rainfall above the 95% percentile of daily rainfall .. so not really short-duration, high-volume, extreme rainfall that causes widespread urban flooding in Ontario.

As reported on this blog, Ontario has regional trends in annual maximum observed rainfall volumes. Charts at right present Environment and Climate Change Canada's Engineering Climate Datasets Version 2.3 trend data. For short durations, less than 6 hour duration, there are four times more statistically significant decreases in maximum rainfall than increases. So southern Ontario regional trends show decreasing rainfall severity. You could "tease out" a teeny, tiny Ontario-wide increase if you average the whole province together, but that would underestimate the increases up north and misstate the decreases down south.

Normalized Catastrophic Losses in Canada

Intact has reported on damage trends in their 'insurance is evolving' webpage. They indicate that "Payouts from extreme weather have more than doubled every five to 10 years since the 1980s." and provide the chart at the right.

So while losses are increasing, how is GDP increasing in Canada? That is, are normalized losses increasing in Canada? Or are those trends like those identified by Peilke? The website tradingeconomics.com provides this Canadian GDP growth chart to the right. Since the early 1980's, GDP has increased about 500% (approximately $300B USD to over $1500B USD). That could explain a portion of the absolute increase in losses since the early 1980's identified by Intact.

* NEW * using Statistics Canada data for expenditure-based Gross Domestic Product and catastrophic loss data presented by Intact Centre for Climate Adaptation have been used to assess normalized losses as a fraction of GDP. While losses have increased significantly, but the normalized Canadian catastrophic losses are up and down. There is a low r-squared upward trend in normalized losses (i.e., not a strong trend). So using Pielke's 'detection vs. attribution' distinction, one could argue there is a detectable trend upward, however the attribution - what caused it - is unclear. As noted below, we have significant quantifiable upward trends in urbanization in Ontario cities over past decades, suggesting increased runoff stresses under a stationary climate, or extreme weather trends.
 Pielke cites a 2014 IPCC report that notes the following:

"Economic growth, including greater concentrations of people and wealth in periled areas and rising insurance penetration, is the most important driver of increasing losses."

Ironic - some more losses are because of rising insurance penetration. Makes sense though. Here are Canadian cat losses normalized based on personal property net written premiums (according to Facts of the Property and Casualty Insurance Industry in Canada 2015 is published by Insurance Bureau of
Canada (IBC), 2015):


Wow! Not much of a trend there to suggest that extreme weather is getting a lot worse - normalized losses are up and down with the maximum relative losses back in 1997 (note the 2014 and 2015 premiums are assumed to be 2% greater than previous years to extend this from 2013 to 2015 where cat loss information was available; similarly 1987-1989 premiums are assumed to increase at 2% to arrive at the reported 1990 value). The r-squared is very low too (0.012) meaning not a strong trend here over time. This muted trend is in stark contrast to the non-normalized losses typically reported by the insurance industry.

Intersection of Vulnerability and Extreme Events

A refreshing observation in Pielke's book is that it is the intersection of intrinsic vulnerabilities and exposure to extreme weather events that causes damages, like flood losses. More properties and belongings in the wrong place explain increased losses. So I made a fancy graphic to explain it:


I just found this infrastructure climate vulnerability Venn diagram in the PIEVC Engineering Protocol
For Infrastructure Vulnerability Assessment and Adaptation to a Changing Climate PRINCIPLES and GUIDELINES, so I guess we can't copyright it.



Note that PIEVC figure above describes infrastructure-climate interaction. Our figure substitutes infrastructure with development, meaning the property impacted by climate (weather). Where does infrastructure come into it? I suppose here:

The Media and Public Opinion

Pielke notes that the reporting on extreme weather has increased considerably, which feeds a public perception that extreme events are increasing in frequency or severity. For example in the New York Times the phrase 'extreme weather' has jumped in popularity in newspaper articles since the mid 1990's.  In this blog we have commented on the 'availability bias' that such frequent reporting can cause, skewing the public's perception on the true probability of events. A common statistical sin in such reports is to declare a record rainfall ... umm ... for a particular calendar day (July 8, 2013 in Mississauga, Ontario, or September 28, 2016 in Windsor/Tecumseh, Ontario). Once engineers start design infrastructure to operate differently on different calendar days of the year, such reporting of calendar day rainfall records will be worthwhile, saintly even. But sorry, that's nuts and not going to happen any time soon.

Key Take Away - Let's Get Back On Track, Put First Things First, and not be so ideologically driven to predetermined conclusions that we miss the obvious stuff.

I love this quote in the Pielke's book :

"There is such a furor of concern about the linkage between greenhouse forcing and floods that it causes society to lose focus on the things we already know on floods and how to mitigate and adapt to them."

Greater Toronto Hamilton Area Urban Growth Affecting Urban Flood Risk
This is from Flood risk and climate change: global and regional perspectives, Zbigniew W. Kundzewicz, Shinjiro Kanae, Sonia I. Seneviratne, John Handmer, Neville Nicholls, Pascal Peduzzi, Reinhard Mechler, Laurens M. Bouwer, Nigel Arnell, Katharine Mach, Robert Muir-Wood, G. Robert Brakenridge, Wolfgang Kron, Gerardo Benito, Yasushi Honda, Kiyoshi Takahashi, and Boris Sherstyukov, Hydrological Sciences Journal Vol. 59 , Iss. 1,2014.

Overland flow explains basement flood risks,
from "flood plain to floor drain".
That reference abstract also notes "Economic losses from floods have greatly increased, principally driven by the expanding exposure of assets at risk. It has not been possible to attribute rain-generated peak streamflow trends to anthropogenic climate change over the past several decades. Projected increases in the frequency and intensity of heavy rainfall, based on climate models, should contribute to increases in precipitation-generated local flooding (e.g. flash flooding and urban flooding)."

Along those lines, in this blog we have tried to expose some of those existing urban flood risks related to:

i) proximity to overland flow paths beyond valley systems (sometimes encumbered major drainage systems), and

ii) increased imperviousness cover in Ontario municipalities (e.g., mid 1960's to late 1990's).

BONUS - Yoda, Twerking, Extreme Weather Correlation

Maybe I didn't learn anything from Pielke's book, like the importance of data and statistical analysis to advance science and public policy. I did learn that the New York Times has a great online tool to analyze the frequency of extreme weather references in their publication. I have used that to help establish some undeniable correlations between extreme weather, twerking and Yoda, as shown in the graphic below.


New York Times Chronicle Tool - Correlation of Extreme Weather, Twerking and Yoda

Spurious correlation between temperature and disaster damages you have found?

Green Infrastructure: Solution to Urban Flooding in Ontario or Overpriced Panacea?

Ontario urban flood damages are real. Green Infrastructure (GI), or Low Impact Development (LID) stormwater management measures have been proposed as the solution to urban flooding as well as water quality impairment, stream erosion, and potable water supply security (aka Source Water Protection in Ontario).  And proponents have cited that it is CHEAPER to rebuild roads with GI or LID, so why not go "all in". It sounds too good to be true, right? The truth is the incremental costs are higher than conventional , so are operational costs. But the absolute costs for achieving targets proposed the Ontario Ministry of Environment and Climate Change (MOECC) are actually PROHIBITIVE, potentially consuming entire municipal capital budgets for decades.

Here's why GI or LID will not be part of Ontario flood risk reduction for our cities 'existing urban development areas. This is discussed under the topics of i) cost, and ii) existing infrastructure and property impacts that can increase flooding. We have included GI / LID retrofit implementation costs for all Ontario municipalities to show the big green pill we would have to swallow.

Background

These GI or LID stormwater Best Management Practices (BMPs) have been used for years to address stream erosion impacts due to change in water balance following development, and have been used to manage water quality impacts through vegetative source and conveyance controls, promoted in Ontario's 1994 Stormwater Management Practices Planning and Design Manual.

On November 15, 2016, the Environmental Commissioner of Ontario released a report, Urban Stormwater Fees: How to Pay for What We Need. The report cites the issues as follows “Stormwater runoff – from heavy rain or snowmelt – can cause flooding, stream or river-bank erosion, and water pollution" and then "calls on the province to require municipalities to recover the full costs of managing stormwater runoff; for example, by charging landowners a separate stormwater fee based on runoff volumes". It also says the "Ontario government should also require all municipalities to prepare asset management plans for both their grey (pipes, drains, etc.) and green (wetlands, green roofs, permeable pavement, rain gardens, etc.) stormwater infrastructure."

The Environmental Commissioner of Ontario is on the right track to promote asset management plans with full lifecycle accounting of infrastructure capital, operating and renewal costs. This is already a requirement for all municipalities by the end of 2016 as a condition of receiving federal Gas Tax funding. But no municipalities have done the deep dive into GI and LID impacts, because to date only demonstration, or pilot, projects have taken place. The demonstration projects often have heavy subsidies (donated profession design time, donated materials) that it is difficult to know the true implementation cost for a project, or the cost for municipal-wide implementation. Until now, so read on.

Proponents of GI and LID such as Credit Valley Conservation have reported that there are on average savings of 25% on road retrofits by applying LIDs:

"LID road retrofits save 25 per cent on average compared to traditional stormwater management practices."(1)

(1) http://www.creditvalleyca.ca/wp-content/uploads/2015/07/Advancing-Low-Impact-Development-as-a-Smart-Solution-for-Stormwater-Management-v1.pdf

And other proponents have reinforced this cost efficiency message, such as Green Communities Canada indicating "The Credit Valley Conservation has produced a number of case studies detailing road right-of-way low impact development projects, and has found that costs are consistently lower than expected and performance has exceeded expectations".

A thorough examination of cost claims reveals there are no such savings or efficiencies - GI or LID projects cost more, and the literature case studies for cost savings (typical rural estate residential developments in the southern US) are not applicable to the sustainable built form communities in most Ontario municipalities where urban flooding issues exist.

Reality Check - Prohibitive Cost of Green Infrastructure, Low Impact Development Retrofits in Ontario

GI / LID demonstration project, literature, and local project costs indicate excessive, prohibitively high costs for implementation when applied to target management areas

Incremental GI / LID implementation costs for additional elements beyond standard design features has been estimated based on completed projects and unit costs for various measures. The incremental, additional cost is $390,000 per hectare of service area (untreated catchment)(1).

The untreated urban area in Ontario is estimated by urban land use area in place in the late 1990’s – early 2000’s and equates to 852,045 hectares(2).

The incremental GI / LID implementation cost is therefore $390,000 x 852,045 = $332,000,000,000, i.e., over $330 billion. As an example, the City of Markham's portion of this cost is $4.18 billion which is considered prohibitive as it is equivalent to 34 times the city’s 2016 capital budget of $122.9 million(3).

Organizations such as Credit Valley Conservation has identified over 140,000 kilometers of municipal roadway in Ontario(4), equating to 281,621 hectares of right of way(5).

The incremental LID implementation cost for roadways alone, assuming no external property runoff is therefore $390,000 x 281,621 = $110 billion. This is considered prohibitive.



(1) CVC, University of Toronto and TRCA demonstration projects per City of Markham analysis.
(2) SOLRIS Version 1.2 land cover GIS mapping, as compiled in the Ontario Land Cover Compilation Version 2.0
(3) City of Markham 2016 Budget, https://www.markham.ca/wps/wcm/connect/markhampublic/129bc6d6-2289-49a2-b199-8893c02af011/2016-Budget-Signed-v2.pdf?MOD=AJPERES&CACHEID=129bc6d6-2289-49a2-b199-8893c02af011
(5) Assuming 20.1 metre, 66 foot right of way width

GI / LID demonstration project, literature, and local project costs indicate only severely limited, technically ineffective implementation of GIs / LIDs can be achieved considering even Ontario’s entire stormwater infrastructure deficit

The entire national infrastructure deficit for water supply, wastewater, stormwater and roads is $170 billion, of which stormwater comprises 23% or $39.1 billion(1). The Ontario stormwater infrastructure deficit has been stated as $6.8 billion (2).

Assuming all Ontario stormwater infrastructure deficit spending is allocated to LID implementation, the area that can be treated is about 17,400 hectares, or 2% of the untreated urban area of Ontario. This would result in an equivalent composite treatment volume of 0.5 mm, assuming a target treatment volume of 25 mm. It is suggested that even this considerable investment, although not prohibitive, would not result in a tangible benefit if only 2% of untreated area is addressed.



(1) Canadian Construction Association, Canadian Public Works Association, Canadian Society for Civil Engineers and Federation of Canadian Municipalities. 2012. Municipal Roads and Water System. Volume 1
(2) Urban Stormwater Fees: How to Pay for What We Need, Environmental Commissioner of Ontario, November, 2016, https://media.assets.eco.on.ca/web/2016/11/Urban-Stormwater-Fees.pdf

GI / LID project implementation costs are more expensive than traditional servicing projects, contrary to promotional documents that indicate 25% savings

The CVC has reported that there are on average savings of 25% on road retrofits by applying LIDs:
"LID road retrofits save 25 per cent on average compared to traditional stormwater management practices."(1)
The reference for the average costs savings is from USEPA (2), but it does not in fact demonstrate such average savings for the two roadway project included in the reference.

The first road project is the 2nd Avenue SEA Street in Seattle Washington. The USEPA gives the convention project cost of $868,803, and LID cost of $651,548, suggesting 25% savings. However the Seattle Public Utilities actual project costs of $850,000 (3) for the LID design suggesting very little savings (only 2.2%).  Seattle Public Utilities notes the high soft cost of associated with LID design as follows "This included an extensive design and communications budget due to the need to work closely with residents on the design."

The second project is Crown Street, Vancouver British Columbia, a street redevelopment project. The project added 79% of the capital cost in consultant design fees and aesthetic design features  (capital cost $396k, consultant and aesthetic design features cost $311k), which is line with Markham’s experience on Glencrest Park Raingarden implementation. The USEAP report notes that “Discounting the extra costs, the $396,000 construction cost is 9 percent higher than the estimated $364,000 conventional curb-and-gutter design cost.” The average cost of roadway LID retrofits is therefore 5-6% more than conventional design, or 38% more than conventional design if additional consultant fees and aesthetic design features are considered – this is 63% higher than the average reduced costs cited by CVC.

Other USEPA case studies are for rural, large lot subdivisions (e.g., Auburn Hills Subdivision, Southwestern Wisconsin, Gap Creek Subdivision, Sherwood Arkansas, Laurel Springs Subdivision, Jackson, Wisconsin, Mill Creek Subdivision, Kane County, Illinois, Prairie Crossing Subdivision, Grayslake, Illinois, Prairie Glen Subdivision, Germantown, Wisconsin) that are not relevant to Ontario urban areas and not relevant to urban roadway retrofits.

Detailed economic studies on source control implementation have acknowledged that implementation of source control (SC) GI / LIDs would be more costly in retrofit settings than in greenfield settings. For example, a study of the Rouge River watershed (4) identified:

“The average per-house costs of the intervention strategies for medium density residential development in urban greenfield areas is $2,785 while the average cost is $4,607 in urban retrofit areas. These values suggest that retrofitting old developments is more costly than integrating best practices into the new development. In addition, the Rouge River Study modeling results suggest that the surface water quality improvements from the urban retrofit areas are less than the surface water quality improvements from urban green field development under the SC (source control) scenario, relative to FBO (uncontrolled full build out).”



(1) http://www.creditvalleyca.ca/wp-content/uploads/2015/07/Advancing-Low-Impact-Development-as-a-Smart-Solution-for-Stormwater-Management-v1.pdf
(4) http://www.greeninfrastructureontario.org/sites/greeninfrastructureontario.org/files/Final%20Rouge%20Report%20Nov%2030.pdf

Reality Check - Existing infrastructure and property impacts of GI / LID infiltration measures have been overlooked

Flooding and operational cost impacts of GI / LID to partially separated wastewater systems have been overlooked

It is commonplace that urban areas built between 1960 and 1980 are serviced by partially separated sewer systems that exhibit high extraneous flow rates during wet weather events. Analysis of historical flooding events in the City of Toronto (May 2000, August 2005, July 2013) demonstrates that the 1961-1980 era developments have the highest relative proportion of reported flooding (1). In the City of Markham, the proportion of properties flooded during the August 19, 2005 extreme rainfall was highest for partially separated properties serviced before 1980, with over 2.5% of properties flooded. In contrast, only 0.3% of fully separated properties were flooded. These data indicate that partially separated sewer systems are at significantly higher risk of flooding than new fully separated areas. Statistical analysis of wet weather flows by the City of Ottawa support the variability in risk for different systems, identifying average 100 year extraneous flow rates of 4.87 L/s/ha in partially separated systems and only 0.57 L/s/ha in newer separated systems (2).

Wastewater systems are sensitive to groundwater conditions that contribute to extraneous flow rates that cause property flooding / sewer back-ups. As indicated in the document Infiltration/Inflow Control/Reduction for Wastewater Collection Systems. A Best Practice by the National Guide to Sustainable Municipal Infrastructure, by the Federation of Canadian Municipalities and National Research Council:

"Uncontrolled infiltration/inflow in sanitary sewers can have very detrimental effects on social, economic and environmental aspects of urban areas. Excessive flows can severely limit the capacity of existing sewer systems to serve expanded populations. They also generate sewer backups, basement flooding and health risks, increase the operation and maintenance costs of the treatment and pumping facilities, and give rise to overflow of wastewater to streets or to watercourses."(3)

And further that inflow and infiltration (I/I) is affected by groundwater levels:

"Groundwater infiltration (GWI) — Flow deriving from groundwater flowing into the sewer cracks in the pipe, manholes, etc. This I/I component tends to be continuous and dependent on groundwater levels. "

City of Ottawa analysis of monitored extraneous flows also identified factors affecting these flows including age of pipe, and noted the importance of groundwater conditions:

“Other factors are more prevalent with respect to extraneous flows such as construction practices, type of material, groundwater levels, etc.” (4)

Given observed flood history data for wastewater systems and infrastructure management best practices, infiltration LID implementation in existing urban areas that is intended to replenish groundwater systems and raising groundwater levels (or have recharge intercepted in trenches or foundation drains in partially separated sewer systems), would put additional stress on wastewater. This would contributing to increased operating costs where infiltrated water enters the wastewater sewer system during moderate conditions, and increased sewer backups and overflows during extreme conditions. Where LID implementation has a tangible benefit on groundwater levels, it will have a tangible dis-benefit on I/I stresses.

The effect of infiltration LIDs on groundwater levels has been identified through numerous monitoring and analysis studies that have demonstrated:

i) local groundwater mounding potential in the vicinity of an infiltration LID, with increases of groundwater level of over 1 m for extreme events (5), and

ii) statistically significant regional scale increases in groundwater level following infiltration LID implementation (6), and

iii) recharge targets of 10 mm will result in extensive groundwater level increases, even up to surface(7).

The US Transportation Research Board in its Evaluation of Best Management Practices for Highway Runoff Control, Issue 565 has identified I/I risks with infiltration BMPs in urban areas:

“In urban areas, unrestricted infiltration may exacerbate infiltration and inflow (I/I) problems in both separate and combined systems; the likelihood of this scenario must be evaluated before constructing unlined infiltration systems.”(8)

Flooding impacts of GI / LID to adjacent properties have been overlooked

Comprehensive analysis of groundwater effects due to LID implementation has been completed for the North Markham Urban Area (Future Urban Area (FUA)), where coupled surface and groundwater modelling at a subwatershed scale allowed effects of groundwater recharge to be assessed in terms of groundwater levels. This comprehensive assessment leverages considerable long-term, investment in the development of the regional groundwater models, refinements to water quantity stress models in three tiers of Clean Water Act refinements, and further analysis refinement at a subwatershed level to refine and calibrate the modelling tools to assess local impacts.

In North Markham, the comprehensive modelling results indicate that groundwater levels will increase above existing levels in some areas even if low LID implementation targets for recharge (i.e., 4 mm event) are implemented. If more moderate targets (10 mm event) are implemented, “Most parts of the FUA show a rise in water table above existing conditions and the potential for ponded water in areas where it rises to ground surface”, according to the Phase 2 analysis report (page 79-80). Based on this detailed modelling, infiltration LIDs implemented in existing urban areas are predicted to impact groundwater levels, which in turn adversely affect I&I stresses as noted above, and also adversely affect adjacent properties.

The MOECC LID design guidance of 25- 33 mm, 625-825% greater than a target that can increase groundwater levels in some areas, and 250-330% greater than a target that can increase groundwater levels in most areas, would clearly increase groundwater levels significantly in most areas, resulting in significantly higher I&I impacts, and adjacent property impacts.

Other jurisdictions have opted to prevent infiltration from LIDs due to adjacent property impacts. This includes the Seattle 2nd Avenue SEA Street swales where groundwater impacts to adjacent properties were identified through engineering analysis:

"Our original hope for retaining flows and allowing infiltration into the native soils throughout the length of the block was not possible because some homes had an existing groundwater intrusion problem. To limit the potential for stormwater to adversely impact the residences of concern, our geotechnical engineers identified some swales that needed an impermeable liner – for example, a six inch depth of natural clay material was used as the preferred material.”(9)

Similarly the Seattle Swale on Yale is lined to prevent water from infiltrating into the ground adjacent to the proposed developments (10).



(1) Analysis by R. Muir: http://www.cityfloodmap.com/2016/04/design-standard-adaptation-vs-climate.html
(2) City of Ottawa, Sanitary Sewer Extraneous Flow Analysis, E. Tousignant, P.Eng., October 1, 2008.
(3) Infiltration/Inflow Control/Reduction for Wastewater Collection Systems, A Best Practice by the National Guide to Sustainable Municipal Infrastructure, Federation of Canadian Municipalities and National Research Council, March 2003 https://www.fcm.ca/Documents/reports/Infraguide/Inflow_Infiltration_Control_Reduction_for_Wastewater_Collection_Systems_EN.pdf
(4) City of Ottawa, Sanitary Sewer Extraneous Flow Analysis, E. Tousignant, P.Eng., October 1, 2008.
(5) Villanova University, The Graduate School, Department of Civil and Environmental Engineering, The Observed Effects of Stormwater Infiltration on Groundwater, Matthew Damien Machusick, 2009
https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjso-_107XQAhWs6YMKHdtPA8gQFggjMAA&url=https%3A%2F%2Fwww1.villanova.edu%2Fcontent%2Fdam%2Fvillanova%2Fengineering%2Fvcase%2Fvusp%2FMachusick%252009Thesis%252004_28_09.pdf&usg=AFQjCNHoQDNxwHISnqTYOPM9le8jHbYYBA&sig2=8VmthXVnITZqjc5Qv8rRJQ
(6) Impact of Storm Water Recharge Practices on Boston Groundwater Elevations, Journal of Hydrologic Engineering 17(8):923-932 · August 2012
https://www.researchgate.net/publication/236325104_Impact_of_Storm_Water_Recharge_Practices_on_Boston_Groundwater_Elevations
(7) North Markham Subwatershed Study, Phase 2 Assessment.
(8) Section 2.2.3.2, https://books.google.ca/books?id=jKR-CF7PG6AC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false
Conclusions


Ontario urban flood damages are real. Readers of this blog know we do our best to explain the causes. In general it is decades-old low design standards, constrained overland flow paths, and increasing imperviousness:


It is not aging infrastructure or extreme weather changes as the Environmental Commissioner of Ontario states - that narrative from the insurance industry has been shown to be incorrect and Engineering Climate Datasets for southern Ontario show mostly statistically significant decreasing trends in extreme rainfall.


The cost to mitigate flooding are also real. If GI / LID is the solution, then the cost is prohibitive - and it would be at best a partial solution because the target storms are smaller than the events that cause flooding in Ontario cities, they may be ineffective for concurrent events (i.e., they are slow draining and may be full with a preceding 'small' storm when the 'big' flood-inducing storm arrives), and can in fact aggravate extraneous flow stresses causing flooding and increased pumping and treatment costs in existing urban areas where flooding is most acute. Here are implementation costs for Ontario municipalities, assuming $390,000 per hectare of untreated runoff and urban areas from the Ontario land use GIS layer:

Table 1 - LID Retrofit Cost per Ontario Municipality


Urban Area Built by 2000 Where LID Retrofit Can Apply per Ontario Land Classification v2 (Hectares)
Retrofit LID Cost at $390k Per Hectare (average unit cost)
City of Barrie
5836
 $              2,275,397,213
City of Belleville
3418
 $              1,332,359,598
City of Brampton
15925
 $              6,208,581,693
City of Brantford
4955
 $              1,931,925,803
City of Brockville
1287
 $                  501,584,398
City of Burlington
8009
 $              3,122,356,516
City of Cambridge
5921
 $              2,308,519,800
City of Clarence-Rockland
2144
 $                  835,827,798
City of Cornwall
2542
 $                  991,133,787
City of Dryden
1861
 $                  725,696,949
City of Elliot Lake
2730
 $              1,064,168,391
City of Greater Sudbury
19652
 $              7,661,598,386
City of Guelph
5678
 $              2,213,801,129
City of Hamilton
24115
 $              9,401,464,058
City of Kawartha Lakes
12128
 $              4,728,354,653
City of Kenora
3367
 $              1,312,596,571
City of Kingston
7458
 $              2,907,682,499
City of Kitchener
8427
 $              3,285,434,384
City of London
17389
 $              6,779,305,984
City of Mississauga
24509
 $              9,555,173,566
City of Niagara Falls
5748
 $              2,240,932,529
City of North Bay
5179
 $              2,019,170,839
City of Orillia
1816
 $                  707,837,418
City of Oshawa
5985
 $              2,333,212,619
City of Ottawa
41720
 $            16,265,094,044
City of Owen Sound
1305
 $                  508,882,595
City of Pembroke
958
 $                  373,558,930
City of Peterborough
3793
 $              1,478,849,856
City of Pickering
4208
 $              1,640,664,574
City of Port Colborne
1914
 $                  746,249,444
City of Prince Edward County
4163
 $              1,623,173,462
City of Quinte West
4647
 $              1,811,707,301
City of Sarnia
5551
 $              2,164,011,985
City of Sault Ste. Marie
7892
 $              3,076,804,186
City of St. Catharines
6170
 $              2,405,396,352
City of St. Thomas
1925
 $                  750,652,924
City of Stratford
1852
 $                  722,205,744
City of Temiskaming Shores
1743
 $                  679,548,131
City of Thorold
1701
 $                  663,320,169
City of Thunder Bay
10507
 $              4,096,288,663
City of Timmins
8338
 $              3,250,583,737
City of Toronto
53697
 $            20,934,317,510
City of Vaughan
12834
 $              5,003,659,847
City of Waterloo
4475
 $              1,744,655,113
City of Welland
3345
 $              1,303,912,418
City of Windsor
10673
 $              4,160,875,955
City of Woodstock
2224
 $                  867,169,696
County of Brant
5686
 $              2,216,581,813
Haldimand County
7119
 $              2,775,288,639
Municipality of Arran-Elderslie
1414
 $                  551,084,070
Municipality of Bayham
1014
 $                  395,155,278
Municipality of Bluewater
1735
 $                  676,521,836
Municipality of Brighton
1321
 $                  514,996,590
Municipality of Brockton
1927
 $                  751,144,149
Municipality of Brooke-Alvinston
850
 $                  331,383,770
Municipality of Callander
128
 $                    49,868,091
Municipality of Central Elgin
2077
 $                  809,731,480
Municipality of Central Huron
1661
 $                  647,390,450
Municipality of Centre Hastings
463
 $                  180,647,927
Municipality of Charlton and Dack
376
 $                  146,604,292
Municipality of Chatham-Kent
13837
 $              5,394,323,927
Municipality of Clarington
5832
 $              2,273,774,416
Municipality of Dutton/Dunwich
1008
 $                  393,111,432
Municipality of French River
807
 $                  314,690,899
Municipality of Gordon / Barrie Island
0
 $                                     -  
Municipality of Greenstone
5313
 $              2,071,521,370
Municipality of Grey Highlands
2502
 $                  975,432,137
Municipality of Hastings Highlands
733
 $                  285,805,125
Municipality of Highlands East
90
 $                    34,973,453
Municipality of Huron East
2131
 $                  830,836,603
Municipality of Huron Shores
1093
 $                  426,172,616
Municipality of Killarney
61
 $                    23,736,685
Municipality of Kincardine
2539
 $                  989,975,900
Municipality of Lambton Shores
2183
 $                  851,038,224
Municipality of Leamington
2894
 $              1,128,141,652
Municipality of Magnetawan
0
 $                                     -  
Municipality of Markstay-Warren
880
 $                  342,927,554
Municipality of Marmora and Lake
580
 $                  226,112,538
Municipality of McDougall
594
 $                  231,498,467
Municipality of Meaford
1860
 $                  725,003,971
Municipality of Middlesex Centre
3003
 $              1,170,606,283
Municipality of Morris-Turnberry
963
 $                  375,392,251
Municipality of Neebing
93
 $                    36,298,005
Municipality of North Grenville
2151
 $                  838,722,516
Municipality of North Middlesex
1751
 $                  682,609,515
Municipality of North Perth
1881
 $                  733,267,074
Municipality of Northern Bruce Peninsula
1822
 $                  710,416,348
Municipality of Oliver Paipoonge
1245
 $                  485,233,629
Municipality of Port Hope
1947
 $                  758,959,886
Municipality of Powassan
520
 $                  202,674,096
Municipality of Red Lake
872
 $                  339,910,030
Municipality of Shuniah
1734
 $                  675,872,717
Municipality of Sioux Lookout
2161
 $                  842,301,440
Municipality of South Bruce
1325
 $                  516,408,861
Municipality of South Huron
1863
 $                  726,258,348
Municipality of Southwest Middlesex
1466
 $                  571,575,162
Municipality of St.-Charles
16
 $                      6,149,082
Municipality of Temagami
1303
 $                  508,101,898
Municipality of Thames Centre
2424
 $                  944,949,883
Municipality of the Nation
2410
 $                  939,485,007
Municipality of Trent Hills
2174
 $                  847,415,441
Municipality of Tweed
1185
 $                  462,172,378
Municipality of Wawa
1540
 $                  600,408,305
Municipality of West Elgin
1243
 $                  484,716,088
Municipality of West Grey
2492
 $                  971,344,445
Municipality of West Nipissing
1339
 $                  522,031,631
Municipality of West Perth
1853
 $                  722,240,831
Municipality of Whitestone
353
 $                  137,630,668
Norfolk County
8760
 $              3,415,266,857
Town of Ajax
3718
 $              1,449,481,629
Town of Amherstburg
2071
 $                  807,371,846
Town of Arnprior
581
 $                  226,314,291
Town of Aurora
2608
 $              1,016,659,934
Town of Aylmer
432
 $                  168,376,078
Town of Bancroft
289
 $                  112,551,886
Town of Blind River
1514
 $                  590,232,933
Town of Bracebridge
2509
 $                  978,204,048
Town of Bradford West Gwillimbury
2047
 $                  797,863,137
Town of Bruce Mines
193
 $                    75,131,081
Town of Caledon
6008
 $              2,342,124,841
Town of Carleton Place
451
 $                  175,867,256
Town of Cobalt
144
 $                    56,315,417
Town of Cobourg
1293
 $                  504,128,241
Town of Cochrane
1164
 $                  453,760,153
Town of Collingwood
1616
 $                  629,890,566
Town of Deep River
537
 $                  209,481,069
Town of Deseronto
103
 $                    40,148,857
Town of East Gwillimbury
2364
 $                  921,792,141
Town of Englehart
199
 $                    77,543,346
Town of Erin
1415
 $                  551,627,926
Town of Espanola
926
 $                  361,094,100
Town of Essex
2053
 $                  800,459,612
Town of Fort Erie
3964
 $              1,545,507,309
Town of Fort Frances
1080
 $                  420,944,581
Town of Gananoque
326
 $                  127,139,509
Town of Georgina
3197
 $              1,246,579,464
Town of Goderich
580
 $                  226,024,819
Town of Gore Bay
0
 $                                     -  
Town of Gravenhurst
1544
 $                  602,074,960
Town of Greater Napanee
2169
 $                  845,687,382
Town of Grimsby
1478
 $                  576,075,133
Town of Halton Hills
3974
 $              1,549,191,495
Town of Hanover
471
 $                  183,437,382
Town of Hawkesbury
557
 $                  217,068,738
Town of Hearst
985
 $                  384,067,632
Town of Huntsville
2378
 $                  927,265,789
Town of Ingersoll
843
 $                  328,655,718
Town of Innisfil
3405
 $              1,327,561,384
Town of Iroquois Falls
2241
 $                  873,695,969
Town of Kapuskasing
1738
 $                  677,425,339
Town of Kearney
0
 $                                     -  
Town of Kingsville
2644
 $              1,030,852,823
Town of Kirkland Lake
1167
 $                  454,918,040
Town of Lakeshore
4206
 $              1,639,673,352
Town of Lasalle
2024
 $                  789,108,809
Town of Latchford
395
 $                  154,077,927
Town of Laurentian Hills
851
 $                  331,629,383
Town of Lincoln
2321
 $                  904,765,938
Town of Marathon
974
 $                  379,664,152
Town of Markham
10732
 $              4,184,077,556
Town of Mattawa
193
 $                    75,367,922
Town of Midland
1307
 $                  509,654,520
Town of Milton
5163
 $              2,012,855,092
Town of Minto
1137
 $                  443,277,766
Town of Mississippi Mills
1400
 $                  545,724,456
Town of Mono
1175
 $                  457,944,336
Town of Moosonee
277
 $                  108,095,775
Town of New Tecumseth
2371
 $                  924,379,844
Town of Newmarket
2963
 $              1,155,229,192
Town of Niagara-on-the-Lake
2538
 $                  989,510,991
Town of Northeastern Manitoulin and the Islands
253
 $                    98,473,032
Town of Oakville
7890
 $              3,076,128,752
Town of Orangeville
1174
 $                  457,593,461
Town of Parry Sound
640
 $                  249,515,892
Town of Pelham
1679
 $                  654,750,050
Town of Penetanguishene
731
 $                  284,989,341
Town of Perth
470
 $                  183,323,347
Town of Petawawa
1503
 $                  586,136,469
Town of Petrolia
419
 $                  163,191,902
Town of Plympton-Wyoming
1450
 $                  565,312,046
Town of Prescott
331
 $                  129,157,039
Town of Rainy River
0
 $                                     -  
Town of Renfrew
520
 $                  202,858,306
Town of Richmond Hill
6032
 $              2,351,554,603
Town of Saugeen Shores
1504
 $                  586,443,485
Town of Shelburne
363
 $                  141,525,379
Town of Smiths Falls
528
 $                  205,665,305
Town of Smooth Rock Falls
776
 $                  302,682,206
Town of South Bruce Peninsula
1837
 $                  716,258,415
Town of Spanish
596
 $                  232,296,707
Town of St. Marys
608
 $                  236,893,168
Town of Tecumseh
2187
 $                  852,634,705
Town of the Blue Mountains
2173
 $                  847,196,144
Town of Thessalon
220
 $                    85,955,571
Town of Tillsonburg
1006
 $                  392,085,123
Town of Wasaga Beach
2033
 $                  792,687,733
Town of Whitby
5046
 $              1,967,074,693
Town of Whitchurch-Stouffville
3244
 $              1,264,781,098
Township of Addington Highlands
261
 $                  101,920,378
Township of Adelaide-Metcalfe
967
 $                  377,058,907
Township of Adjala-Tosorontio
1340
 $                  522,549,171
Township of Admaston/Bromley
660
 $                  257,322,857
Township of Alberton
82
 $                    31,798,035
Township of Alfred and Plantagenet
1731
 $                  674,863,952
Township of Algonquin Highlands
744
 $                  290,208,605
Township of Alnwick/Haldimand
1707
 $                  665,328,927
Township of Amaranth
835
 $                  325,594,335
Township of Armour
407
 $                  158,735,791
Township of Armstrong
151
 $                    58,964,522
Township of Ashfield-Colborne-Wawanosh
1712
 $                  667,285,055
Township of Asphodel-Norwood
759
 $                  295,901,549
Township of Assiginack
0
 $                                     -  
Township of Athens
472
 $                  183,858,432
Township of Atikokan
546
 $                  212,910,871
Township of Augusta
1479
 $                  576,461,095
Township of Baldwin
436
 $                  170,165,540
Township of Beckwith
854
 $                  332,769,726
Township of Billings
0
 $                                     -  
Township of Black River-Matheson
4110
 $              1,602,287,635
Township of Blandford-Blenheim
1357
 $                  529,110,531
Township of Bonfield
231
 $                    90,034,491
Township of Bonnechere Valley
0
 $                                     -  
Township of Brethour
2
 $                         807,012
Township of Brock
1704
 $                  664,434,196
Township of Brudenell, Lyndoch and Raglan
0
 $                                     -  
Township of Burpee and Mills
0
 $                                     -   
Township of Calvin
291
 $                  113,551,880
Township of Carling
95
 $                    36,938,352
Township of Carlow/Mayo
0
 $                                     -  
Township of Casey
23
 $                      8,842,047
Township of Cavan-Monaghan
1674
 $                  652,469,363
Township of Central Frontenac
0
 $                                     -  
Township of Central Manitoulin
0
 $                                     -  
Township of Centre Wellington
2596
 $              1,012,045,930
Township of Chamberlain
252
 $                    98,385,313
Township of Champlain
1361
 $                  530,575,434
Township of Chapleau
412
 $                  160,437,534
Township of Chapple
0
 $                                     -  
Township of Chatsworth
1562
 $                  608,934,564
Township of Chisholm
0
 $                                     -  
Township of Clearview
2436
 $                  949,739,325
Township of Cockburn Island
0
 $                                     -  
Township of Coleman
762
 $                  296,998,033
Township of Conmee
165
 $                    64,455,714
Township of Cramahe
1071
 $                  417,611,270
Township of Dawn-Euphemia
1299
 $                  506,610,680
Township of Dawson
0
 $                                     -  
Township of Dorion
573
 $                  223,568,695
Township of Douro-Dummer
1180
 $                  460,023,269
Township of Drummond/North Elmsley
1091
 $                  425,295,429
Township of Dubreuilville
465
 $                  181,297,045
Township of Ear Falls
545
 $                  212,586,312
Township of East Ferris
227
 $                    88,578,361
Township of East Garafraxa
570
 $                  222,305,545
Township of East Hawkesbury
765
 $                  298,050,658
Township of East Luther Grand Valley
450
 $                  175,516,382
Township of East Zorra-Tavistock
1080
 $                  420,979,668
Township of Edwardsburgh/Cardinal
1394
 $                  543,557,804
Township of Elizabethtown-Kitley
2054
 $                  800,889,433
Township of Emo
0
 $                                     -  
Township of Enniskillen
888
 $                  346,059,112
Township of Essa
1631
 $                  635,837,895
Township of Evanturel
160
 $                    62,227,658
Township of Faraday
15
 $                      5,745,576
Township of Fauquier-Strickland
853
 $                  332,743,411
Township of Front of Yonge
546
 $                  212,945,958
Township of Frontenac Islands
556
 $                  216,656,460
Township of Galway-Cavendish and Harvey
1481
 $                  577,320,738
Township of Gauthier
0
 $                                     -  
Township of Georgian Bay
1426
 $                  556,031,406
Township of Georgian Bluffs
2060
 $                  803,187,664
Township of Gillies
0
 $                                     -  
Township of Greater Madawaska
0
 $                                     -  
Township of Guelph/Eramosa
1496
 $                  583,118,946
Township of Hamilton
1958
 $                  763,494,944
Township of Harley
214
 $                    83,508,219
Township of Harris
78
 $                    30,455,939
Township of Havelock-Belmont-Methuen
760
 $                  296,103,302
Township of Head, Clara and Maria
617
 $                  240,559,810
Township of Hilliard
46
 $                    17,903,390
Township of Hilton
56
 $                    21,815,645
Township of Hornepayne
732
 $                  285,199,866
Township of Horton
498
 $                  194,279,415
Township of Howick
861
 $                  335,506,550
Township of Hudson
0
 $                                     -  
Township of Huron-Kinloss
1621
 $                  632,048,446
Township of Ignace
778
 $                  303,261,150
Township of James
0
 $                                     -  
Township of Jocelyn
0
 $                                     -  
Township of Johnson
0
 $                                     -  
Township of Joly
13
 $                      5,035,054
Township of Kerns
0
 $                                     -  
Township of Killaloe, Hagarty and Richards
0
 $                                     -  
Township of King
3119
 $              1,215,930,544
Township of La Vallee
0
 $                                     -  
Township of Laird
0
 $                                     -  
Township of Lake of Bays
978
 $                  381,137,827
Township of Lake of the Woods
113
 $                    43,859,359
Township of Lanark Highlands
420
 $                  163,928,739
Township of Larder Lake
0
 $                                     -  
Township of Laurentian Valley
1053
 $                  410,383,247
Township of Leeds and the Thousand Islands
2142
 $                  835,257,627
Township of Limerick
148
 $                    57,631,197
Township of Loyalist
1653
 $                  644,539,591
Township of Lucan Biddulph
682
 $                  265,726,310
Township of Macdonald, Meredith and Aberdeen Additional
54
 $                    20,973,545
Township of Machar
96
 $                    37,438,349
Township of Machin
1104
 $                  430,330,484
Township of Madawaska Valley
0
 $                                     -  
Township of Madoc
382
 $                  148,806,032
Township of Malahide
1462
 $                  569,838,332
Township of Manitouwadge
1150
 $                  448,532,117
Township of Mapleton
1607
 $                  626,688,832
Township of Matachewan
0
 $                                     -  
Township of Mattawan
108
 $                    42,280,422
Township of Mattice-Val Cote
380
 $                  148,200,773
Township of McGarry
0
 $                                     -  
Township of McKellar
0
 $                                     -  
Township of McMurrich-Monteith
0
 $                                     -  
Township of McNab/Braeside
911
 $                  355,015,193
Township of Melancthon
849
 $                  331,173,246
Township of Minden Hills
1215
 $                  473,874,055
Township of Montague
664
 $                  259,050,916
Township of Moonbeam
459
 $                  178,832,149
Township of Morley
0
 $                                     -  
Township of Mulmur
850
 $                  331,445,174
Township of Muskoka Lakes
293
 $                  114,209,770
Township of Nairn and Hyman
726
 $                  283,059,529
Township of Nipigon
788
 $                  307,296,211
Township of Nipissing
130
 $                    50,640,016
Township of North Algona Wilberforce
68
 $                    26,377,018
Township of North Dumfries
1298
 $                  506,084,368
Township of North Dundas
1796
 $                  700,030,452
Township of North Frontenac
804
 $                  313,278,627
Township of North Glengarry
1948
 $                  759,503,742
Township of North Huron
711
 $                  277,103,428
Township of North Kawartha
265
 $                  103,192,299
Township of North Stormont
1340
 $                  522,487,768
Township of Norwich
1629
 $                  635,171,232
Township of O'Connor
4
 $                      1,614,024
Township of Opasatika
264
 $                  102,867,740
Township of Oro-Medonte
3791
 $              1,478,139,334
Township of Otonabee-South Monaghan
1442
 $                  562,329,609
Township of Papineau-Cameron
665
 $                  259,173,722
Township of Pelee
190
 $                    74,210,035
Township of Perry
616
 $                  240,094,901
Township of Perth East
2200
 $                  857,739,934
Township of Perth South
1090
 $                  424,769,117
Township of Pickle Lake
857
 $                  333,936,385
Township of Plummer Additional
53
 $                    20,657,758
Township of Prince
556
 $                  216,577,513
Township of Puslinch
1231
 $                  480,093,312
Township of Ramara
2010
 $                  783,740,424
Township of Red Rock
537
 $                  209,516,156
Township of Rideau Lakes
2222
 $                  866,257,421
Township of Russell
1399
 $                  545,496,388
Township of Ryerson
0
 $                                     -  
Township of Sables-Spanish Rivers
2525
 $                  984,589,971
Township of Schreiber
192
 $                    74,964,416
Township of Scugog
2526
 $                  984,625,059
Township of Seguin
626
 $                  243,963,297
Township of Severn
2678
 $              1,044,150,980
Township of Sioux Narrows-Nestor Falls
0
 $                                     -  
Township of Smith-Ennismore-Lakefield
2575
 $              1,003,949,492
Township of South Algonquin
835
 $                  325,629,423
Township of South Dundas
2419
 $                  942,897,265
Township of South Frontenac
2213
 $                  862,617,095
Township of South Glengarry
2597
 $              1,012,510,839
Township of South Stormont
2190
 $                  853,731,189
Township of Southgate
1530
 $                  596,513,594
Township of South-West Oxford
1464
 $                  570,890,956
Township of Southwold
1255
 $                  489,330,093
Township of Springwater
2971
 $              1,158,316,891
Township of St. Clair
3090
 $              1,204,570,971
Township of St. Joseph
0
 $                                     -  
Township of Stirling-Rawdon
803
 $                  313,059,330
Township of Stone Mills
1276
 $                  497,400,215
Township of Strathroy-Caradoc
1955
 $                  762,065,129
Township of Strong
420
 $                  163,849,792
Township of Tarbutt and Tarbutt Additional
0
 $                                     -  
Township of Tay
1054
 $                  411,093,769
Township of Tay Valley
548
 $                  213,805,602
Township of Tehkummah
0
 $                                     -  
Township of Terrace Bay
747
 $                  291,348,948
Township of the Archipelago
420
 $                  163,867,336
Township of the North Shore
1170
 $                  456,268,908
Township of Tiny
2636
 $              1,027,633,546
Township of Tudor and Cashel
113
 $                    44,201,462
Township of Tyendinaga
916
 $                  357,111,670
Township of Uxbridge
2328
 $                  907,493,990
Township of Val Rita-Harty
1082
 $                  421,795,452
Township of Wainfleet
1088
 $                  424,312,980
Township of Warwick
897
 $                  349,550,317
Township of Wellesley
1148
 $                  447,426,862
Township of Wellington North
1766
 $                  688,688,422
Township of West Lincoln
1809
 $                  705,065,506
Township of White River
556
 $                  216,788,038
Township of Whitewater Region
1730
 $                  674,285,008
Township of Wilmot
1896
 $                  739,319,666
Township of Wollaston
0
 $                                     -  
Township of Woolwich
2576
 $              1,004,098,614
Township of Zorra
1813
 $                  706,740,934
United Townships of Dysart, Dudley, Harcourt, Guilford, Harburn, Bruton, Havelock, Eyre and Clyde
563
 $                  219,647,668
Village of Burk's Falls
154
 $                    59,920,656
Village of Casselman
239
 $                    93,201,137
Village of Hilton Beach
0
 $                                     -  
Village of Merrickville-Wolford
508
 $                  198,156,583
Village of Newbury
59
 $                    22,903,357
Village of Oil Springs
92
 $                    35,798,009
Village of Point Edward
305
 $                  119,007,984
Village of South River
170
 $                    66,438,157
Village of Sundridge
180
 $                    69,990,765
Village of Thornloe
5
 $                      2,096,477
Village of Westport
2
 $                         666,662
TOTAL
                852,045
         $ 332,178,923,064
total hectares
total cost

The Environmental Commissioner of Ontario is right that we have to look at costs to address water resource management challenges in the province, including flooding. We have good models for this in the realm of Source Protection under the Clean Water Act has developed locally-driven, evidence based, semi-quantitative risk management policies for the significant risk. That process has also adopted cost-effective risk prevention policies to prevent future risks from occurring.

We can learn from the 15 year post-Walkerton Source Protection process that risks are not universal, nor are the appropriate solutions. For example, potable water quantity risks are not universal across the province: there are “more than 970 wellhead protection areas and 150 intake protection zones within the source protection areas in Ontario”[1]  But only 22 municipal systems have required Tier 3 water quantity stress assessments[2], indicating that water quantity stresses were confirmed at the earlier Conceptual, Tier 1 or Tier 2 evaluations. Of these systems with Tier 3 assessments, only 18 are groundwater systems that would require recharge management policies – this represents a very small fraction of potable water supplies. Applying this to urban flood risk areas would also show a high variability in risk and required solutions (Toronto basement flooding densities vary from > 4 properties per hectare to less than 0.5 per hectare depending on the topography / slopes).

Unfortunately, Green Infrastructure and Low Impact Development stormwater management measures have been proposed as a universal solution, regardless of local issues to address. regardless of more cost effective pollution prevention measures (ban fertilizers like we did with pesticides), regardless of clearly prohibitive implementation costs, and regardless of impacts to existing wastewater systems in existing urban areas.

When something is promised to solve all our problems and cost less, it is a "Trumpesque" proposition at best. Fulsome economic analysis shows that Green Infrastructure and Low Impact Development stormwater management measures are unaffordable for Ontario urban retrofits, and fulsome technical analyses shows that implementation would be counter productive for flood risk reduction where infiltration is already a chronic challenge in many Ontario cities, and should not be aggravated by additional recharge from well-meaning GI and LID measures.



[1] http://conservationontario.ca/what-we-do/source-water-protection
[2]  Personal communication with Program Services Section, Ministry of Natural Resources & Forestry