City, conservation authorities prepare for hefty spring melt

With spring weather in sight, local conservation authorities are cautioning about the likelihood of flooding.

According to Environment Canada, rain and thunderstorms are expected to begin Friday night and into Saturday. With highs Saturday reaching 12 C, much of the leftover snow is expected to melt.

The City of Ottawa says the mix of rain and melt will contribute to higher water levels in the Rideau, South Nation and Mississippi watersheds.

The Rideau Valley Conservation Authority has issued a flood watch for the Ottawa River in light of current forecasts.

“The long-range forecast indicates a sustained warming trend beyond this timeframe, with continued snowmelt expected into next week,” a notice reads. “While the exact timing and magnitude of rainfall remains uncertain, conditions are favouring a strong, accelerated melt.”

By the end of January, the City of Ottawa had already recorded 143.5 cm of snow, more than the typical 120 to 130 cm. The conservation authority says that snowmelt is expected to rise rapidly, which will put extra strain on the watershed system.

“If these warmer temperatures persist, coupled with rainfall, runoff may increase and could produce flooding in low-lying areas, including ditches, stormwater systems, and areas with limited drainage capacity,” it says.

The Mississippi Valley Conservation Authority has yet to issue a warning for the Carp River or Mississippi River, but has released a flood outlook statement to inform about the potential for flooding.

“Water levels and flows are currently below normal due to a lack of mid-winter snowmelt and rainfall events,” it says. “The snowpack, however, is currently well above average at about 150 per cent of normal for snow water equivalent and depth.”

The City of Ottawa says its Spring Flood Taskforce is now monitoring water levels on the Rideau and Ottawa rivers and is “ready to respond to potential impacts from this spring’s melt”.

While flows in the local watershed typically increase from mid-March to mid-April, the city says snowmelt in the northern regions of the Ottawa River happens later in the season, meaning the river reaches peak flow throughout April and early May.

The taskforce also works with the local conservation authorities to monitor water levels and prepare two to four-day forecasts. The city says these forecasts help to prepare and respond to flooding by opening sandbag filling stations and protecting key infrastructure.