Message # 2020-03
Issued: 5:00 p.m., Wednesday January 15, 2020
Subject: FLOOD WATCH issued for Otonabee River.
Issued to: Municipalities of Selwyn, Douro-Dummer, Asphodel-Norwood, Otonabee-South Monaghan, Cavan Monaghan, City of Kawartha Lakes, City of Peterborough and Trent Hills, as well as ORCA’s other partners in flood emergency management.
This FLOOD WATCH is issued to alert municipalities, residents and businesses that flood conditions are a possibility.
As a result of last weekend’s warm air temperatures and rainfall, inflows from the Haliburton Lakes to the Kawartha Lakes have increased. Trent-Severn Waterway is responding by spilling excess water on the Kawartha Lakes downstream through the Otonabee River. High flows along the Otonabee River cause not only high water levels, but also results in increased turbulence, especially as the water passes over the numerous dams between Lakefield and Peterborough.
Beginning tonight, there will be a return to extreme cold air temperatures, which in turn will cool the surface water temperature of the Otonabee River. Normally, this would result in the formation of a solid cover of ice over the Otonabee River. However, the high, turbulent flow of the Otonabee River prevents the formation of a cover of sheet ice. Without a cover of sheet ice, the surface water temperature will cool below the freezing point (i.e., super-cooled). Unable to form a solid cover of ice, the super-cooled water will instead encourage the formation of “frazil” ice crystals – a kind of slush ice.
As frazil ice flows downstream it will eventually come to rest against obstructions (e.g., islands and bridge piers), in low velocity areas (bends and slope reductions) or in areas of channel constrictions. Where it comes to rest, it will accumulate. Where frazil ice accumulates, it is likely to cause a restriction of water flow downstream, thereby resulting in a rise of water, and possibly flooding, behind the frazil ice jam. Thus, there is potential for flooding on the Otonabee River due to frazil ice generation, accumulation and jamming during this period of extreme cold air temperatures and turbulent water flows. Therefore, residents and businesses in low-lying areas along the shores of the Otonabee River are strongly encouraged to take action to limit or prevent damages.
This FLOOD WATCH message will be up-dated FRIDAY, January 17th, 2020.
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Gord Earle | Flood Forecasting & Warning Duty Officer | 705-745-5791 x 214
250 Milroy Drive, Peterborough, ON K9H 7M9
orcafloodduty@otonabeeconservation.com | Flood Watch Hotline 705-745-5791 x 228