Learn more about Markham's Flood Control & Stormwater
What is Markham’s Flood Control Program?
In February 2013, Council approved a long-term 30-year Flood Control Program which sets funding requirements to achieve level of service improvements for drainage systems in the City of Markham.
The Flood Control Program is a long term, City-wide initiative to improve storm drainage capacity and limit surface and basement flooding risks in urban areas. Improvements will provide a more consistent level of service across Markham and help protect both public and private property. The program will also make critical infrastructure more resilient to climate change and extreme weather.
The City has prioritized the assessment and upgrade of older drainage systems, constructed prior to 1978, when modern day standards for stormwater drainage were implemented. Areas constructed prior to 1978 are more susceptible to flooding as they were not designed to convey the amount of water expected during infrequent, very large storm events.
The Citywide Flood Control Program includes projects that range from major capital improvements to the storm system, to education programs and subsidies for residents to improve their private plumbing systems.
Staff updated the cost estimates in 2018 for all phases of the Flood Control Program, with an estimated cost of $367-$382M. To date, the City has received two funding grants for the program:
- $6.5M from the Clean Water and Wastewater Fund (CWWF) – Ministry of Infrastructure of Ontario
- $48.6M from the Disaster Mitigation and Adaptation Fund (DMAF) – Infrastructure Canada
In 2013, Council approved the allocation of $2M per year from the Federal Gas Tax Grant. The costs of the program are otherwise funded by the City’s stormwater fee, charged to all property owners; residential and non-residential. This fee is applied to the Final Tax bill for each property owner in Markham. For more information, visit Stormwater Fee
Flood Control Program Projects
The City has prioritized the upgrades within West Thornhill, the Don Mills Channel (Woodbine/Denison Area) and Markham Village and Unionville, based on the known locations of basement flooding clusters. Other areas within the City will be assessed at a later date. The current status and location of all areas to be assessed through the program are shown in the maps below.
For more information on our flood control projects, please see the following links below:
- Don Mills Channel
- West Thornhill
- Markham Village & Unionville
- Private Plumbing Protection Program
To help fund the program, a Stormwater Fee is charged to all properties in the City of Markham. This fee, combined with revenue from the Canada Gas Tax and other grants, will provide dedicated funds for both approved and future Stormwater infrastructure improvement projects City-wide.
Pursuant to the City of Markham’s By-law 2019-100 “The Non-Residential Stormwater Fee rate of $29.00 per $100K of CVA is to be adjusted to compensate for the average change in CVA.” The resulting annual adjustments to the non-residential Stormwater Fee rate are summarized in the table below:
||Non-Residential Rate per $100,000 in CVA
||%2 increase, adjusted for average change in CVA
The adjusted non-residential Stormwater Fee rate is not retroactive – it is applicable to the year in which it was adjusted.
Council Decisions and Resolutions:
- Project Needs Workshop (May 15, 2012)— see Workshop Presentation and Workshop Minutes
- Recommendations for a City-Wide Flood Control Strategy (November 8, 2012)— General Committee Presentation and General Committee Minutes
- Council Decision Regarding Flood Control Strategy (February 12, 2013)— see Council Presentation and Council Minutes
- Feedback from Community Meetings (June 10, 2013)— see General Committee Report, Community Information Meeting summary and General Committee Minutes
- Framework on Annual Flood Control Strategy Costs (Gas Tax) (October 28, 2013)— see Presentation and Council Resolution
- Annual Flood Control Strategy Costs (Stormwater Fee) (November 18, 2013)— see Presentation and Council Resolutions
- Stormwater Funding Implementation and Communication Plans (May 26, 2014)— see Presentation and Council Resolutions
- West Thornhill Flood Remediation (June 24/25, 2014)— see Presentation and Council Resolutions
- Status Update on Implementation of Stormwater Fee (November 25, 2014)— see Presentation, Report, Bylaw, and Council Resolutions
- Business Consultation Meetings (April 9, 2015 & April 14, 2015 )— see Presentation
- Stormwater Fee Non-Residential Consultation and City-Wide Implementation (June 15, 2015)— see Report
- Stormwater Fee Non-Residential Consultation and City-Wide Implementation (September 9, 2015)— see Memorandum
- Flood Control Program and Stormwater Fee Update (April 8, 2019)— see Report
- Council Meeting Flood Control Program and Stormwater Fee Update (September 24, 2019)— see Report and Presentation
Don Mills Channel Flood Protection
If you own, manage or are renting a property within the Don Mills Channel area, your property and assets may be at risk due to flooding damage during intense thunderstorms.
The Don Mills Channel is a man-made channel that runs through the commercial & industrial section of the Woodbine Ave and Denison Street area. Several of the private properties and roads in this area are prone to flooding during large storm events. Major roads in the area, including Woodbine Avenue, can also be impassable during severe storms.
The reason this area is at higher risk of flooding is its limited capacity for carrying floodwater. The current system of storm sewers, open channels, and culverts was designed in the 1960’s to carry moderate storm events. The system does not have adequate capacity to handle stormwater during intense rainfall events.
Damage to property and assets may occur during severe thunderstorms and flooding.
The City has also developed a Floodprooing and Education Program to assist property owners and tenants within this area to identify site-management and floodproofing measures to protect their properties and assets against flood damage.
On August 19, 2005, the West Thornhill community was impacted by a severe rain storm during which stormwater runoff exceeded the capacity of drainage systems, causing extensive flooding of private property and roadways. The storm was characterized by high rainfall intensities and volumes which resulted in the flooding of many basements in homes and institutions as well as watercourse erosion, and damage to the City’s infrastructure such as roads, culverts, sewers and watercourses
A Class Environmental Assessment (EA) study for the West Thornhill Stormwater Flood Remediation Study was completed and approved in August 2011. The purpose of the Class EA study was to:
- Identify and understand the causes of flooding in the study area;
- Develop a range of alternative solutions to increase capacity and reduce flood risks in West Thornhill;
- Identification and prioritization of the causes of basement flooding and surface flooding;
- Evaluation of various flood remediation measures and develop a comprehensive remediation plan for the areas identified as highest priority and most likely to flood again in the future.
The following Preferred Alternative was proposed from the findings in the Class EA Study for the West Thornhill Stormwater Flood Remediation Study:
- Roof downspout disconnections;
- New inlet control devices in catchbasins that limits the inflow to sewers;
- Increased sewer inlet capacity at key locations where sewer capacity is available; and,
- Storm sewer upsizing and inlets within and downstream of the high flood potential areas as well as ‘diversion’ pipes that reduce flows at critical locations relieving overloaded sewers.
This multi-phase program will reduce the risk of basement flooding. It will also limit environmental concerns caused by directly connecting downspouts to the sanitary sewer system. These connections increase the flow of rainwater into the sanitary sewer system during heavy or long rain events. This can cause:
- The sanitary sewer system to overflow
- Sanitary sewer backups
- Basement flooding
This program also enforces the existing City of Markham Sewer By-Law # 2014-71 (PDF) [Clauses 3.1D & 19.11]. It also enforces the Region of York’s Sewage and Land Drainage By-Law # S-0064-2005-009, which prohibits the discharge of roof drainage water into the sanitary sewer system.
This program will be done in five phases, but this is subject to change.
Phase 1 Program Area: The first phase of the program began in May, 2013 within the Thornhill area. The investigations and testing work within the Phase 1 Area (PDF) was finished in April 2014. The downspout disconnection work has been finished. Flow monitoring within the area started in Spring/Summer 2016.
Phase 2 Program Area: The second phase of the program began in May, 2014 within the Thornhill Area. The investigation and testing work with Phase 2 Area (PDF) was finished in April 2015. The notice of disconnection was mailed out to affected homeowners in June, 2015. The downspout disconnection work has been finished. Flow monitoring within the area commenced in Spring 2017.
Phase 3 Program Area: The third phase of the program began in May, 2015. It covered areas within Thornhill, Milliken, and Unionville. The investigation and testing work within the Phase 3 Area (PDF) ended in April, 2016. The downspout disconnection work has been finished.
Phase 4 Program Area: The fourth phase of the program began in May, 2016 within the Markham Area. The investigations and testing work within the Phase 4 Area (PDF) ended in February 2017. The notice of disconnection was mailed out to affected homeowners in September 2017.
Phase 5 Program Area: The fifth phase of the program began in May 2017, which covers area within Thornhill and Unionville. The investigation and testing work within the Phase 5 Area (PDF) was completed in November 2017. The notice of disconnection will be mailed out to the affected homeowners in Fall 2018 and the disconnection period will end in Fall 2019. Post condition flow monitoring within the area will commence in Spring/Summer 2020.
Phase 5 Expansion Program Area: The fifth phase expansion of the program began in September 2017, which covers area within Thornhill and Markham Village. The investigation and testing work within the Phase 5 Expansion Area (PDF) has been starting since November 2017.
Phase 6 Program Area: The sixth phase of the program began in September 2017, which covers areas within Unionville and Markham Village. The investigation and testing work within the Phase 6 Area (PDF) will commence in June 2018.
Steps taken by City to identify downspout discharge locations
Before any downspouts are disconnected, the City needs to confirm whether the downspouts that go into the ground are actually connected to the municipal sanitary sewer system. To do this, the City takes following steps:
- Preliminary property investigation
We do general surveys of residential lots to see whether downspouts are discharging above the ground or into the ground.
- Sanitary & storm sewer smoke testing
We do smoke testing within the sanitary and storm sewer systems. This involves blowing a non-toxic, highly visible smoke through the systems and observing the exit points of the smoke. This test finds whether downspouts that go into the ground are connected into the sanitary sewer system or the storm sewer system. The smoke test also identifies other devices/equipment that are connected to the underground sewer system.
Identified downspouts that discharge into the municipal sanitary sewer system
After the investigations and testing are finished, the City will send a Notice of Disconnection to homes with downspouts connected to the sanitary sewer system. The notice will tell you which downspouts within your property need to be disconnected. We will send you more information about how to disconnect a downspout and use rain barrels when the downspout disconnection stage starts.
Financial Assistance Plan
Markham Council has approved a Financial Assistance Plan for the Sanitary System Downspout Disconnection Program. This will help homeowners with the cost to disconnect downspouts from the sanitary sewer.
Only homeowners who receive a disconnection notice from the City will be eligible.
- The City will reimburse 80% of the cost for completing the downspout disconnection, up to a maximum of $500;
- The City will reimburse 100% of the cost for a rain barrel purchased by the home owner, up to a maximum of $150.
Ask for Partial Cost Reimbursement
You can ask for part of your costs to be paid by the city. Follow these steps:
- Fill out the Financial Assistance Application Form (PDF) and send it to the City. Include all original/photocopy receipts by mail, e-mail, or fax. Please write "Downspout Disconnect - Financial Assistance Application" in your submission.
- Once the City receives your application package, City staff will contact you to inspect the disconnected downspouts.
- Once the City sees that the downspouts have been disconnected properly, we will process your application and send you a cheque.
How to disconnect a downspout
- Ensure there is a suitable area for the water to discharge from the downspout
- Ensure downspouts are disconnected and drained properly away from the foundation walls and directly to a storage device (e.g. a rain barrel), your lawn, or garden.
- When disconnecting downspouts, remember not to drain directly onto neighbouring properties, lanes, or sidewalks.
- Extend your downspout to discharge water at least 1 metre from any structure's foundation (including your neighbour’s) or public sidewalk, and 2.5 metres from retaining walls.
- Ensure the ground slopes away from the house for a minimum of 1 metre.
- Use a splash pad to help direct the flow of water and protect against erosion.
- Ensure eavestroughs are clean and drain properly.
- Obtain professional advice and service from a knowledgeable and licensed roofer, eavestrough contractor, or civil engineer.
Read this Step-by-step procedure to disconnect your downspouts (PDF)
Using Rain Barrels
Rain barrels collect water from downspouts and rooftops and decrease the amount of storm water runoff that leaves your property. Using a rain barrel can help you lower your water bill and improve your lawn and garden.
here to learn more about rain barrels.
Help is only a phone call away! Waterworks staff will be more than happy to help you. Please call us at 905.477.5530.
Stormwater Facilities Overview
Stormwater management facilities, or stormwater ponds, have been used to control stormwater from urban areas in Markham since the late 1980s, intended to ensure that new development does not increase or change the conditions for downstream landowners. When first introduced, most stormwater ponds were dry, and designed to store water in order to prevent flooding and erosion downstream. They have evolved over time to also include a permanent pools of water, used to trap sediment and prevent contaminants from our roads and subdivisions from entering our watercourses.
While ponds can appear as attractive, natural features and are often surrounded by trails and parks, the public is encouraged to exercise caution around facilities, as conditions in stormwater management ponds can change rapidly due to fluctuating water levels and hazards associated with deep pools, fast moving water at inlets and outlets, and thin ice.
As of May 2020, the city owns and maintains 123 stormwater ponds. Several new facilities are added in the City of Markham each year.
The City has a program to remove sediment from each pond, a practice that is completed at a frequency mandated by the Ministry of Environment, Conservation and Parks. This activity, called dredging, is undertaken approximately every 20 years, and involves draining the pond and removing the sediment that has been captured by the pond. City staff confirm the theoretical frequencies by periodically measuring actual sediment levels.
Sediment Excavation During Pond Cleanout
In addition, the City conducts a full inspection of each stormwater facility every year to make sure that it is performing as originally designed. Based on these annual inspections, general maintenance is performed as required. This includes litter pickup, vegetation management, and removal of any blockages in the infrastructure at each pond.
Visit Environmental Services Current Projects for or further information on ongoing projects.
Algae Growth and Colour Sheens
Stormwater ponds are designed to trap contaminants in order to protect the downstream watercourse, and in several situations, this means that the pond itself may not be the most aesthetically pleasing. The growth of algae in stormwater ponds, while not aesthetically pleasing, is a common occurrence, especially during hot and dry summers. The contaminants trapped by a stormwater pond will often contain nutrients, which promote the growth of algae. The degree that algae grows in a pond is driven by a variety of factors, which are very difficult (or impossible) to control.
From time to time, colour sheens are observed on pond water surfaces. Often these sheens have rainbow-like appearance. In some cases, a reddish precipitate can also be seen in the water where these sheens occur. While colour sheens may be caused by petroleum spills, they are often a result of the contaminants that are trapped in the specific pond. Generally, if no petroleum odour is present, this is likely not a petroleum spill. If you observe a colour sheen in the pond, please contact the City and we will investigate.
For more information, please contact:
Robert Muir Manager, Stormwater
Phone: 905.477.7000 x 2357
City Wide Erosion Master Plan
Under the City-Wide Stream Erosion Master Study Implementation Plan, the City of Markham has established a systematic, five-phase process for identifying, inspecting, prioritizing, and restoring creek erosion sites within the City.
The study was previously completed in 2007 (Aquafor Beech Ltd.) and in 2013/2014 (AECOM). In 2018/2019, the study was undertaken by the City, and peer reviewed by Greck & Associates. Through an annual erosion inspection program, the City monitors about 900 sites across all 19 watercourses in the City that may be susceptible to erosion.
The City uses information collected through the inspection program to prioritize work, and then completes restoration of sites as required to minimize risks to public safety, infrastructure and the environment. The City updates its 5 year plan for addressing erosion sites on an annual basis.
Information about current erosion restoration projects may be found under Current Projects.
Emergency Erosion Sites
River systems are dynamic, and the year over year changes are difficult to predict. The City has an emergency erosion program to restore any sites that were not identified through the erosion master plan process, if an immediate threat to public health and safety, or the City’s infrastructure exists.
The City has a policy, established in 2014 and revised in 2016, that speaks to how the cost associated with the implementation of erosion restoration projects is shared among the City, private landowners and the Toronto and Region Conservation Authority (TRCA). City funding for erosion site restoration comes from Development Charges, Life Cycle Replacement and Capital Reserves based on the 2007 endorsed guidelines. In some situations, funding for erosion restoration may be the responsibility of private landowners. See links to council reports below for further details.
Council Decisions and Resolutions
Swan Lake is situated in the City of Markham at the intersection of Sixteenth Avenue and Williamson Road.
A gravel pit in the 1960s and 1970s, Swan Lake, is currently a community feature near the heart of Historic Markham Village, surrounded by multiple trails, a playground and urban development.
Given that Swan Lake is an old gravel pit, the water in the lake tends to be very stagnant, which has led to poor water quality, and there have been reports of water quality issues since the area around the Lake was developed in the mid-1990s. In 2012, the City initiated a monitoring program of the Lake to measure and monitor the water quality. Due to high phosphorus levels, significant algal blooms were present during the summer months.
Council authorized a chemical treatment to help improve the Lake water quality, and in 2013, 25 tonnes of Phoslock (A non-toxic clay product capable of removing phosphorus from the water and capping phosphorus in the bottom sediment ) was applied across the Lake. Phoslock treatment resulted in a 60% reduction in total phosphorus in the surface and mid-layers of the Lake and increased water clarity.
Over time, the nutrient levels in the Lake have risen again due to the presence of Canada Geese in Swan Lake Park and through release from sediment.
In 2020, the City developed a water quality improvement strategy for Swan Lake, and the Council supported the study recommendations, including a chemical treatment program commencing in 2021.
In August 2021, 13 tonnes of Poly Aluminum Chloride (PAC) were applied to the Lake in a controlled manner over several days. Preliminary observations and testing indicated promising results with this application. Phosphorus concentration after treatment dropped by about 75% and water clarity increased by about 100%.
A long-term Management Plan was received by Markham Sub Committee in November 2021 and approved by the Council in December 2021, including provisions for chemical treatment every three years.
Annual Monitoring Program
Water quality monitoring of Swan Lake has been conducted annually since treatment in 2013 to track water quality and the continued effectiveness of the Phoslock. The ongoing monitoring program allows for continuous assessment of the water quality in Swan Lake and will be used to help establish a long-term plan for water quality improvement in Swan Lake.
Algal Bloom and Toxicity
High nutrient concentrations, and a lack of sufficient water circulation in Swan Lake, has resulted in the growth of different groups of algae, including green algae, diatoms and bluegreen algae (a.k.a. cyanobacteria). Blooms of cyanobacteria are not only unsightly when they form scums on the Lake surface, but they may also produce toxins such as Microcystins, which is toxic to humans, pets, and wild animals upon contact or ingestion.
While the presence of blue-green algae is rare, the City has restricted access to the Lake as a precaution. Residents and/or their pets should not enter the Lake.
Geese are the primary external source of nutrients in the Lake. Therefore, active geese management is completed annually. The geese control program started in 2014, focusing on resident geese. The program extended to the management of migratory geese in 2016.
In 2020, the City reviewed additional geese management measures in consultation with subject matter experts and area residents. Council approved additional hazing and the installation of nine strobe lights to be implemented immediately.
Geese management activities were further enhanced in 2021 through more frequent hazing, removing existing nests and eggs, and relocating resident geese to a farm away from the Lake.
While the waterfowl number in Ontario has been reported to have doubled over the last ten years , the Swan Lake geese population has decreased since the inception of the geese control program, indicating the efficacy of the program.
A volunteer program was also initiated through which residents can submit observations about the geese present at the Lake through a survey application. For more information on how to collect and submit geese counts, please see these instructions.
The current fish community in Swan Lake mainly consists of Common Carp (non-native), Brown Bullhead, and Fathead Minnow. This composition is not considered well-balanced, and the bottom-feeding species are also detrimental to the longevity of chemical treatments. These species were removed from the Lake before the 2021 chemical treatment. Once the water quality improves, the City will work with agencies to develop a fish management plan, which may include stocking with more desirable fish species.
- Update on Swan Lake Water Quality (February, 2013)— see Report
- Swan Lake Water Quality Improvement Program (June, 2020)— see Presentation
- Geese Management at Swan Lake: Overview of Options and Path Forward (September, 2020)— see Presentation
- Swan Lake Long Term Management Plan (November 2021)— see Presentation
For more information, please contact:
Robert Muir, Manager, Stormwater
Phone: 905.477.7000 x 2357