Flood Watch Issued for Rideau River and North Gower; Elevated Flows May Lead to Localized Flooding

Flood Watch Issued for Rideau River and North Gower; Elevated Flows May Lead to Localized Flooding

Short-term cooling and the potential for a significant freezing rain event are forecast across the Rideau Valley Watershed between March 10 and 12. Daytime temperatures are expected to fall toward or below freezing as a series of low-pressure systems approach the region. As precipitation transitions to freezing rain, total amounts of 20 to 40 mm are possible, with freezing rain accumulation of 10 to 20 mm.

Water levels and flows across the watershed are currently elevated due to sustained snowmelt and rainfall that began over the weekend. With the watershed already in an active melt period, additional precipitation may lead to further increases in water levels and flows, with some locations potentially approaching flood onset levels, particularly in flood-vulnerable areas.

A Flood Outlook statement is in effect for the entire watershed. A Flood Watch is being issued for portions of the Rideau Valley Watershed, including the Long Reach of the Rideau River (Merrickville to Kars) and the North Gower area (Stevens Creek and Taylor Drain), where water levels may approach or exceed flooding thresholds if precipitation totals approach the upper range of the forecast.

More Details: 

Weather Forecast: Environment and Climate Change Canada is forecasting a significant mixed-precipitation event across the Rideau Valley Watershed on March 11. Precipitation may begin as rain before transitioning to freezing rain as temperatures fall toward or below the freezing mark. Freezing rain accumulation of 10 to 20 mm is possible, with total precipitation amounts of approximately 20 to 40 mm expected through the event. The exact precipitation type and timing remain uncertain and will influence the amount of runoff generated across the watershed.  

Environmental Conditions: The watershed is currently experiencing sustained freshet conditions following rainfall and accelerated snowmelt over the past weekend. As a result, water levels and flows across the watershed remain elevated. With the watershed already responding to ongoing meltwater runoff, additional precipitation from the upcoming weather system may push flows higher and could lead to localized flooding in flood-vulnerable areas. 

Risks: The entire watershed remains under a Water Safety status, with localized regions under a Flood Watch. The following risks are present:

• Due to uncertainty in temperature, precipitation type, and total precipitation amounts, additional melt and/or rainfall may contribute to further increases in water levels and flows.
• Under rapid melt conditions, existing river ice may weaken and mobilize. The movement of ice can contribute to localized ice jam formation, which can cause sudden water level increases and flooding in vulnerable areas.
• Slippery or unstable banks
• Localized ponding or minor flooding in low-lying areas
• With the risk of significant ice accretion (freezing rain), utility outages are possible.

Location-Specific Considerations: Water levels and flows across the Rideau Valley Watershed may increase, with localized flooding possible in low-lying areas, including ditches, swales, and stormwater drainage features. Locations with known ice-related concerns may also experience unstable or shifting ice conditions as flows increase.

Rideau River – Merrickville to Kars (Flood Watch)

With the forecast precipitation expected over the coming days, water levels and flows may increase along the Rideau River through the Long Reach between Merrickville and Kars.

While widespread flooding along this reach is not currently anticipated, some historically flood-vulnerable shoreline communities may experience impacts if precipitation totals approach the upper range of the forecast. These areas include Hilly Lane, Fairmile Road, Rideau Glen Lane, Lorne Bridge Road, Fennel Lane, Eligh Lane, Cedar Beach Road, Harris Road, and Riverview Lane.

In these locations, water levels could rise to thresholds where minor residential flooding has occurred historically. If higher precipitation totals are observed, water levels may continue to rise later this week, with peak levels potentially occurring between March 13 and March 15. Residents in these communities are encouraged to monitor conditions closely and prepare accordingly. 

North Gower – Stevens Creek & Taylor Drain (Flood Watch):

Due to the elevated flow conditions and the potential for additional rainfall, a Flood Watch is being maintained for the North Gower region. Water levels and flows in Stevens Creek and the Taylor Drain may rise again following the precipitation expected on March 11 and could exceed flood onset levels.

Residents in the City of Ottawa can check flood risks in their area using our Neighbourhood Flood Maps. If your property is within the RVCA watershed, use our Map your property tool to assess potential flooding impacts. Current water levels, flows and flood onset limits can also be reviewed on our Interactive Map.

Action & Safety Recommendations: Residents are advised to exercise caution when near rivers, streams, and other waterbodies due to the risks summarized above. Parents should inform their children of these dangers and provide appropriate supervision. Residents in flood-prone areas are advised to closely monitor water levels and flows and take the necessary precautions to protect their property, such as: 

• Ensuring sump pumps are clear, in good working condition, and have a backwater valve;
• Keeping a portable backup generator and pump easily accessible;
• Ensuring downspouts are clear and directing water at least 3 m away from the dwelling;
• Securing items that could float away as water levels rise;
• Removing valuable items from basements or lower floors that could be subject to flooding;

• Keeping emergency phone numbers handy;
• Familiarizing yourself with your municipality’s Emergency Preparedness Plan.

Backup power for sump pumps will be critically important as freezing rain may cause power outages concurrent with increased flood risk.

Residents are reminded that a Water Safety Statement is in effect until April 30th and advised to exercise caution when near rivers, streams, and other waterbodies due to the risks described above. Parents should inform their children of these dangers and provide appropriate supervision.

Duration: The Flood Outlook and Flood Watch included in this statement are in effect until Friday, March 20, at 11:59 pm or until an update has been issued.