Lyle Larsen
Food Hazard Technician
Water Stewardship Division
Ministry of Environment
Kevin Brown and Don Schaffer
Public Information Officers
Emergency Operations Centre
David Dyer
Chief Engineer
City of Prince George
Grant Bain
Manager
Long Range Planning
City of Prince George
Dan Milburn
Manager
Current Planning & Development
City of Prince George
Nechako River
December 12, 2007
Prince George
Quick Facts
Ice Jam Events
- Since 1917 - 27 Ice Jam Events
- Since 1956 – 22 Ice Jam Events
- Dec 1996 – Most Recent Major Ice Jam Event
- Dec 2007 – Present Day Event
Why Do Ice Jams Occur In Prince George?
- River gradient is quite flat throughout floodplain.
- Length of the flat river channel.
- Reduced water velocities.
- Confluence is five times the normal channel width.
- Shallow water at confluence.
- Gravel bars throughout the lower reach.
- Channel constrictions.
- Bends in the river (6).
- Numerous islands impede ice floes.
- Fraser River surface ice cover.
Three elements play a major role in the severity of the event
- Temperature.
- Water discharge.
- Length of open water upstream (frazil ice production).
What caused the current flood situation?
Low temperatures beginning in late November continued through to December 10th when temperatures dropped to close to minus 30° Celsius. These weather conditions caused freezing of the Fraser River at the confluence of the Nechako and Fraser Rivers. Ice frazil on the Nechako joined into chunks or pans, and accumulated against the frozen Fraser River. These large accumulations of ice then constricted the channel which resulted in high water levels causing the overland flooding.
Options Considered
The City and partnering agencies will look at all solutions to prevent future ice jam and flood events including:
- Dredging
- Permanent dikes and pumping solutions
- Upstream controls
- Early warning systems
- Land use changes
Long Term Plans
The City is currently undergoing negotiations with the Province concerning the scope and cost of a long term study. The study itself is expected to take approximately seven months to complete with the total time estimated at 14 months due to the need to consult with the public, various field experts and involved agencies. The Solicitor General has assured the City that the issue is on the fast track to move forward.
In terms of what is planned for next year should a similar situation in river arise, based on a risk assessment we will leave the temporary berms and dikes in place until a permanent solution is determined. The situation will continue to be monitored.