flood outlook for lake ontario and upper st lawrence river

Due to elevated water levels on both Lake Ontario and the Upper St. Lawrence River, Cataraqui Conservation is putting area residents, municipalities, visitors, and other stakeholders on early notice as to the potential for flooding in the coming weeks.

Much of eastern Ontario and a large portion of the Ottawa River basin received 60 – 90 mm of rain, about a month’s worth, over the past several days, leading to water levels that are well above average for this time of year.

The International Lake Ontario – St. Lawrence River Board (ILOSLRB), which manages water levels and outflows from Lake Ontario through the Moses-Saunders Dam in Cornwall, is reporting a Lake Ontario water level of about 75.32 metres IGLD85 (75.28 m GSC), as of May 3. This level is already nearly 0.3 metres above a typical summer peak water level, which usually occurs in June.

The ILOSLRB’s May 4 forecast suggests the level will continue rising and is expected to reach 75.37 metres IGLD85 (75.33 m GSC) within the next few days and may hit a seasonal peak of approximately 75.45 metres IGLD85 (75.41 m GSC) in the next couple weeks. Even higher water levels are possible if weather and water supply conditions are wetter than average. Current forecasts indicate the peak level of Lake Ontario should remain approximately 0.3 – 0.5 metres below the record highs of 2017 and 2019, which saw water levels as high as 75.9 metres GSC.

Risks: Heightened risks for localized impacts may start to develop with water levels above 75.3 metres GSC, including potential shoreline flooding, beach submersion, crawl space and septic system inundation, and wave-driven erosion during wind events with sustained elevated southwest winds which can increase water levels at the east end of Lake Ontario. Waves generated by high winds can also increase shoreline impacts during times of elevated lake levels.

In 2019, minor flooding was being reported once water levels rose above 75.5 metres GSC. This is when some low-lying roadways started to be impacted and some shoreline properties were experiencing localized impacts. The current ILOSLRB forecast suggests peak water levels will remain 0.05 – 0.10 m (5 – 10 cm) below this level.

In 2019, reports of more severe flooding occurred when water levels rose above 75.7 metres GSC (e.g., further impacts to structures and roadway flooding). The current ILOSLRB forecast suggests similar water levels are unlikely in the forecast period.

Recommended Actions: Residents in flood-prone or low-lying areas which are historically susceptible to flooding, are advised to consider removing items stored in the floodplain.

Keep up to date with the resources provided below under “Additional Information.”

If you witness flooding and/or require assistance, your first point of contact is the local municipality. Preparations are ongoing in the event that water levels rise to the level necessitating the use of sandbags. If this were to occur, affected residents are advised that sand and bags are available at the following municipal locations (watch for Cataraqui Conservation updates or check with your municipality, as availability and location details may change):

Town of Greater Napanee: Sand will be located at the following four locations free to all residents who require it for sandbags:

  1. 8321 CR2 main yard in Greater Napanee located at main gate
  2. Intersection of Abrams RD and CR9 near the fire department dry hydrant
  3. South shore RD at the Dorland fire station Napanee station 3 near road and fuel pump
  4. CR8 works yard South Fredricksburg

Sandbags can be acquired by calling 613-563-8406

Loyalist Township: Individual property owners requiring sandbags for localized flooding should call 613-386-7351 x 116

City of Kingston: Creekford Road Public Works site. Residents should submit a request through Contact Us https://www.cityofkingston.ca/city-hall/contact-us, or call 613-546-0000, and arrangements can be made to have someone meet them on site

Township of Leeds and the Thousand Islands: Township Office located at 1233 Prince Street, Lansdowne, far back parking lot, right hand side, across from the Sand Dome. Signage is located to direct residents and businesses – call first (613-659-2415)

Town of Gananoque: Sand is located at the gate of the Public Works Yard at 665 Charles St. N., if required for localized flooding. If residents require assistance or have questions, they are encouraged to call the Public Works Office at (613) 382-2149 x 1613 or e-mail pwinfo@gananoque.ca

Township of Front of Yonge: (Contact municipality to inquire about availability)

Township of Elizabethtown-Kitley: Not currently available, but affected residents are encouraged to report flooding issues to 613-345-7480, e-mail: mail@ektwp.ca, website: www.ektwp.ca so the municipality can follow up directly. Further assistance maybe available.

City of Brockville: (Contact municipality to inquire about availability)

Township of Augusta: (Contact municipality to inquire about availability)

Additional Information:

For further information on water levels, wind and wave forecasts, and Provincial flood messages visit https://cataraquiconservation.ca/pages/flood.

For information directly from the International Lake Ontario – St. Lawrence River Board (ILOSLRB) visit:

Cataraqui Conservation staff will continue to monitor ILOSLRB water level forecasts, Surface Water Monitoring Centre Provincial Statements, local water levels, and update messaging as needed. This Shoreline Conditions Statement will remain in effect until (or updated before) June 30, 2023, at 11:59 PM.

See below for watershed conditions terminology:

Normal: No flood conditions exist

Shoreline Conditions Statement – Water Safety: Higher than average water levels, unsafe banks, or other factors that could be dangerous for recreational users and shoreline residents. Widespread flooding is not expected.

Shoreline Conditions Statement – Flood Outlook: Early notice of the potential for flooding based on weather and lake conditions.

Flood Watch: Flooding is possible in specific watercourse or municipalities. Municipalities, emergency services and individual landowners in flood-prone areas should prepare.

Flood Warning: Flooding is imminent or already occurring in specific watercourses or municipalities. Municipalities and individuals should take action to deal with flood conditions. This may include road closures and evacuations.