Message # 2020–04
Issued: 3:30 p.m., Friday January 17, 2020
Subject: FLOOD WATCH – UPDATE 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, and Otonabee Conservation’s other partners in flood emergency management.
This FLOOD WATCH is issued to alert municipalities, residents and businesses that flood conditions on the Otonabee River are a possibility. Frazil ice generation on the Otonabee River could lead to ice jamming, which in turn, could lead to a restriction of water flow downstream, thereby resulting in a rise of water, and possibly flooding, behind the frazil ice jam.
The Haliburton Lakes are hydrologically connected to the Kawartha Lakes, which are connected to the Otonabee River.
Last weekend, the Haliburton Lakes Region experienced an invasion of moisture-laden sub-tropical air from the south. This resulted in a pronounced thaw during which air temperatures were significantly warmer than normal and a month’s worth of rain fell over 36-48 hours.
As a result of the rainfall and snowmelt run-off from this event, the Gull River, Burnt River, Mississauga River, Nogies Creek, Eels Creek and Jack Creek are now delivering an unseasonably high volume of water from the Haliburton Lakes to the Kawartha Lakes. These inflows are refilling the Kawartha Lakes part way through their winter drawdown period, resulting in a loss of storage capacity on the Kawartha Lakes, which is an important ingredient for mitigating potential flooding and flood damages, particularly during the spring run-off period.
To regain loss storage on the Kawartha Lakes, the Trent-Severn Waterway has increased water outflows on the Otonabee River. A side-effect of increasing water outflows increased turbulence, especially as the water passes over the numerous dams between Lakefield and Peterborough. In turn, turbulent flows, when combined with cold air temperatures and open water flows, produce frazil ice crystals – a collection of loose, slush-like ice crystals formed in super-cooled turbulent water.
The subsequent sticking and accumulation of frazil ice to objects in the Otonabee River can lead to a restriction of water flow downstream, resulting in a rise of water, and possibly flooding behind the frazil ice jam.
So far, there is no indication that frazil ice is causing any restrictions of water flow downstream, but residents and businesses in low-lying areas along the shores of the Otonabee River are strongly encouraged to take action to protect themselves and to limit or prevent damages. Otonabee Conservation staff will continue to monitor conditions throughout the weekend.
This FLOOD WATCH message will next be up-dated MONDAY, January 20th, 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