Ottawa River flooding could reach May 2017 level in some areas

The Ottawa River Regulation Planning Board is warning residents who live along the Ottawa River that water levels are rising after a weekend of heavy precipitation and could be similar to May 2017 in some areas.

A major weather system brought more than 40 mm of rain to the Ottawa region over the weekend and the board says any remaining snow in the north has melted and run off into the river.

"Minor flood levels are occurring in multiple locations between Mattawa and the Montreal region," the board says. "Major flood levels are expected to be exceeded in flood prone areas over the next few days."

The board says that some areas could see levels similar to or in excess of where they were in May 2017, but water levels should still be 45 cm to 1 m below historic 2019 levels.

Based on the latest weather forecasts and information available as of Monday, the Ottawa River Regulation Planning Board says the following conditions are expected along the main stem of the Ottawa River over the coming week:

A map of the various areas across the region along the main stem of the Ottawa River that will see water levels exceeding peak levels based on the latest weather forecasts and information available as of Monday, May 1, 2023.

Mattawa: Minor flooding is already occurring. Levels are expected to continue rising until they reach a peak of about 154.55 – 154.60 m on Thursday. This corresponds to a rise in level of 45 to 50 cm compared to the observed level on Monday at 8 a.m.

Pembroke: Minor flooding is already occurring. Levels are expected to continue rising until they reach a peak of about 113.30 m 113.35 m Tuesday or Wednesday. This corresponds to a rise in level of 40 to 45 cm compared to the observed level on Monday at 8 a.m.

Whitewater Region: Levels are expected to exceed peak levels observed last week (April 21-23) by 50 to 55 cm. Flows at that location are expected to slightly exceed those experienced in early May 2017.

L'Isle-aux-Allumettes and Lake Coulonge: Levels are expected to exceed peak levels observed last week (April 21-23) by 50 to 55 cm. Levels at Lake Coulonge are expected to be similar to those observed in early May 2017.

McNab-Braeside, Arnprior and Chats Lake: Levels are expected to exceed peak levels observed last week (April 21-23) by 30 to 35 cm. These levels are lower than those observed in early May 2017.

Constance Bay, Aylmer and Lake Deschenes: Levels are expected to exceed peak levels observed last week (April 21-23) by 25 to 30 cm. These levels are lower than those observed in early May 2017.

Gatineau and Hull to the Montreal region: Levels are expected to exceed peak levels observed last week (April 21-23) by 50 to 60 cm in Gatineau (Hull marina) and Thurso. These levels are approximately 70 cm lower than those observed in early May 2017.

Water levels had stabilized last week prior to the significant rainfall. A flood warning was issued for the lower Ottawa River from Arnprior to Hawkesbury last Friday.