By Sue Tiffin
With warmer weather comes the spring thaw, or freshet, as snow and ice accumulated over the winter season melts into rivers, lakes and streams.
Typically throughout central Ontario, the freshet occurs between mid-March to the end of April, lasting several weeks on larger river systems and watersheds, and with environmental factors such as extreme temperatures and more frequent severe storm/rain events impacting the length and severity of the spring freshet each year.
“Currently, this year’s freshet has been gradual with multiple freeze and thaw events as a result of substantial temperature fluctuations and nominal precipitation events,” said Jeff Wiltshire, resource management co-ordinator, Peterborough district, for the Ministry of Northern Development, Mines, Natural Resources and Forestry.
Across the Burnt River and Gull River watersheds, Wiltshire said the last few years were indicative of an average spring freshet, but it is difficult to predict how the freshet will “play out in any year,” depending on the frequency and severity of storm events such as heavy rain, and significant spikes in daytime temperature highs and overnight lows that remain above freezing.
“In the upper reaches of our watersheds, substantial snowpack remains, which has yet to melt,” he said. “As we progress into April the potential for high double-digit temperatures and significant rain events increases. As with any freshet, conditions can change quickly, and it is important to be prepared.”
Key factors considered during a freshet, said Wiltshire, are snowpack, the snow water equivalent in a snowpack (which describes the amount of liquid water in the snowpack that would be formed if it were completely melted), temperatures, rainfall and frozen or unfrozen ground conditions and characteristics of the watershed. The unknown element, he said, is potential for a storm event or combination of events to impact the rate at which the freshet occurs and exacerbate those elements.
“Floods are typically caused by melting snow, ice jams, high lake levels, heavy rains and thunderstorms,” said Wiltshire. “They can happen at any time of year in urban and rural areas. It is important for residents to be prepared especially during the spring freshet.”
Creating a 72-hour emergency preparedness plan and kit, testing sump pumps regularly, putting weather protection sealant around basement windows and ground-level doors, extending downspouts at least two metres from the home to move water away from the building and regularly maintaining water drainage systems such as weeping tile, culverts and ditches are included in the preparation guidance offered by Emergency Management Ontario.
Visit ontario.ca/page/floods for further information on how to prepare for a flood, what to do in the event of a flood and to access links to flood forecasting and warning information.