There is a moderate risk of flooding in the Grand River watershed this spring, according to Stephanie Shifflett, a water resources engineer with the Grand River Conservation Authority (GRCA).
Shifflett was speaking Feb. 20 at the annual meeting of municipal flood co-ordinators at the GRCA office in Cambridge. They were gathered to hear the spring flood prognosis and receive an update on the flood warning system used by the GRCA to alert municipalities and residents of flood conditions.
After an exceptionally dry winter in 2012, conditions are closer to normal this year, said Shifflett.
Snowfall was above average in January, and is already about average in February, with a week left to go. However, most of the January snow melted away during two warm spells that month.
“The snow pack has been rebuilding since the large snowfall of Feb. 8,” she noted.
Snow cover in the northern part of the watershed, including parts of Dufferin and Wellington counties, is just below normal. The central portion, including Waterloo Region and the Guelph area, is only about half of normal. The southern portion, from Brantford to Lake Erie, is about normal.
The risk of flooding from ice jams is also moderate this year. Most rivers and streams are ice covered, but at this time there is only one notable ice jam, just upstream of Dunnville. There is the potential for more ice jams if there is a rapid melt that moves upstream ice downstream quickly. Ice jams can be an unpredictable cause of flooding because they can form quickly. Water backs up behind them and spills out of the river banks, sometimes inundating communities.
The GRCA operates seven reservoirs, including Conestogo Lake, Belwood Lake and Guelph Lake to store water from the spring runoff. This results in smaller flood peaks downstream of the reservoirs.
About 60 per cent of the flood storage space is available in the reservoir system. Water levels in the reservoirs are a bit higher this year than most, but can be lowered as weather and watershed conditions change.
The risk of lake surge flooding on the Lake Erie shoreline in Haldimand County is low this year because of low water levels. Lake surge flooding occurs when winds from the west or southwest push water to the eastern section of the lake, causing a rise in water levels along the shore.
