Flood warning for Mattawa. Potential flooding on Nipissing

A flood warning continues today for the Mattawa River subwatershed including the Town of Mattawa, according to the North Bay-Mattawa Conservation Authority (NBMCA).

A flood watch continues for all other areas in the NBMCA watershed while a "watershed conditions statement" is now in effect for the Lake Nipissing shoreline.

“A significant rainfall event is forecast to bring around 50 mm of precipitation from Saturday into Tuesday," noted Angela Mills, NBMCA Duty Officer. "Higher amounts of rain are possible. As well, based on information from the Ottawa River Regulation Planning Board, there is an increase in outflow from reservoirs in the Abitibi-Timiskaming region. There is potential for further water level increases in both the Ottawa River and Mattawa River at the Town of Mattawa.”

The Lake Nipissing water level has increased by 29 cm since April 21.

"The lake level is expected to increase further into early next week, with the forecasted significant rain event. A Flood Outlook is now in effect for the Lake Nipissing shoreline area, as an early notice for the potential of flooding,” said Chitra Gowda, NBMCA CAO. “Conditions are changing rapidly, and water levels may increase beyond what is forecast.”

The water level on Lake Nipissing is regulated by dams operated by the federal government. Current water levels can be viewed by searching for the Station Name “Lake Nipissing” on this website.

The Ottawa River water levels are managed by dams and reservoirs operated by provincial and federal governments. The flow of the Ottawa River at Mattawa has increased in the last few days, along with the water levels at upstream reservoirs. The Ottawa River water level at Mattawa has increased by about one metre (100 cm) in the past week. The Ottawa River Regulation Planning Board posts current data and forecasts on its website.

A Flood Watch continues for all other areas in the NBMCA watershed. With the ground saturated and water levels at or above normal, the water levels of local creeks, rivers, and lakes are expected to increase. Urban watercourses including Chippewa Creek may experience a quick rise in response to intense rainfall.

For comparison, when river-based flooding occurred in April 2019, rainfall of 24.2 mm was measured April 26, 2019. The snowpack water content was 15 mm (measured April 24, 2019).

Residents, especially those in low-lying areas, are encouraged to monitor the conditions as they develop and prepare accordingly. Shorelines of creeks and rivers will be very slippery at this time and, when combined with cold open water, pose a serious hazard. The public is encouraged to keep children and pets away from watercourses and shorelines.