Thursday, 28 April 2011

River Break 2011

The above two photographs I was able to capture on the way home from work on Thursday April 21st, 2011. It was unfortunate that I missed the initial breakup but I was still quite excited that it was still moving until it jammed by the water treatment plant.

The above photo is Fort McMurray in 1997 after river break.
Most rivers flow north to south when spring progresses. Snowmelt, therefore, flows into areas that are already melted by warm spring weather. The Athabasca River adjacent to the Lower Town Site of Fort McMurray is different. It flows south to north. When southern snowmelt enters the Athabasca River, it eventually flows into ice formations further north that have not yet weakened. As it flows downstream (north) some years, it breaks the solid ice, resulting in a dynamic breakup. On other years, it melts the ice and a thermal breakup occurs.
Thermal and Dynamic Break UpsThe type of breakup (thermal or dynamic) is dependent on weather and river conditions. Thermal processes melt the ice cover and weaken it. Contributing factors include: sunshine or wind, increased water or air temperature. Dynamic processes push the ice cover out of its original place. Contributing factors include: increased precipitation, increased water levels, water movement which causes the ice cover to break before it has weakened. Dynamic processes are usually associated with higher flood risk, especially in the Fort McMurray area.

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