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GRCA Issues Flood Warning Update for Lake Ontario Shoreline

Flood Potential: High

The Ganaraska Region Conservation Authority advises that water levels on Lake Ontario reached a new record peak of 75.92 meters above sea level (masl), which was last recorded on June 15th.  Since then water levels have slowly declined and are now sitting at 75.73 masl as measured at Cobourg today. With outflows set at 10,400 m3/s since June 13th, which is above the maximum limit of Plan 2014 and dry weather in the forecast, the lake level will continue its slow decline over the coming weeks. The actual rate of decline is dependent on the amount of precipitation received in the basin.

Lake Erie continues to provide record inflows (via the Niagara River) for this time of year and with all the Great Lakes experiencing high water levels it is expected that Lake Ontario will continue to see above average water levels for the time of year even as they decline. The International Lake Ontario – St. Lawrence River Board (ILOSLRB) predicts the water level will decline by 5 to 8 cm per week and reach a level of 75.5 masl in late August with normal amounts of rainfall.

The main concern during high lake levels is shoreline erosion and flooding of low-lying shorelines including dynamic beaches and wetlands along the shore. Shortened beaches, waterfront trails and shoreline protections may be damaged by wave action especially during strong onshore winds.

While this Flood Warning is in effect, shorelines may be slippery with unstable banks and bluffs may be actively eroding. Residents are asked to exercise caution around our shorelines and to alert any children in their care of these dangers.

This Flood Warning for the Lake Ontario shoreline was first issued on May 13th and will remain in effect through at least August 22nd, 2019. Conservation Authority staff will continue to monitor conditions, and provide updates as necessary. Should you have any questions or wish to report flooding, please contact the following GRCA staff at 905-885-8173.

Mike Smith                                                    
Flood Operations Officer                               

Note: A Flood Warning is issued as notice that flooding is imminent or already occurring in specific watercourses or municipalities.