GRCA Issues Updated Flood Warning

Flood Potential: High

The Ganaraska Region Conservation Authority advises that 35 to 40mm of rain has fallen over the past 24 hours and another 20 to 25mm is forecast to fall between this afternoon and tomorrow. Streams in our area are flowing at bankfull levels and starting to flood in low spots along their banks.

With the forecast rainfall this afternoon, water levels and flows are expected to increase even more resulting in heavier flooding adjacent to watercourses. Small streams will flood first and contribute high flows to the larger systems, such as the Ganaraska River, which is likely to experience peak flows later this evening or overnight. As runoff makes its way to the streams, it will cause high flows in ditches and on some roadways and ponding in low lying areas.

Lake Ontario water levels are already very high and will increase slightly as a result of heavy runoff. Where high flowing streams meet high lake levels, there is an increased chance of flooding, particularly at the outlet of the Ganaraska River, Gages Creek, Cobourg Creek and at several other watercourse outlets. With the high water conditions, there is a substantial risk of erosion along the shoreline of Lake Ontario and along stream banks particularly near bridges, culverts and retaining walls.

Rice Lake is currently rising but is not yet close to flood critical levels. This Flood Warning does not apply to Rice Lake, however residents should expect to see the water level rise over the next week as the Trent-Severn Waterway continues to manage the runoff from this and previous rain events.

The public and especially children are warned to stay well back from the shorelines of Lake Ontario and the local streams within the GRCA jurisdiction. Driving through flood water is not recommended. Fast flowing water in combination with slippery or flooded stream banks is creating very hazardous conditions and these areas should be avoided.

This Flood Warning for the Lake Ontario shoreline and the watersheds draining to Lake Ontario and Rice Lake will be in effect through Sunday, May 7th, 2017. 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

Mark Peacock, P.Eng.
Flood Forecasting and Warning Coordinator

Note: A Flood Watch is issued as notice that flooding is possible in specific watercourses or municipalities. Municipalities, emergency services and individual landowners in flood-prone areas should prepare.