2017 flooding caused by extreme weather, agency says

Extreme weather and recordsetting water supply conditions were the cause of flooding along Lake Ontario and the St. Lawrence River last year, a new report from the Lake Ontario-St. Lawrence River Board found.

The report, released early this month by the board, provides a detailed account of the flooding and what the board did to reduce the water levels on the lake and river.

A release from the board, which is part of the International Joint Commission, said that during the winter of 2017 flows were set to avoid ice jams under highly variable temperatures.

“In spring and early summer, the flows were repeatedly adjusted to reduce and balance upstream and downstream flooding. The board made every effort to minimize impacts and maintain the highest possible outflows without threatening navigation safety.”

Lake Ontario, the release said, started 2017 slightly below its long-term average level and rose a record-breaking 1.4 metres (about 4.5 feet) by late May.

“This was due to extreme wet conditions in the Lake Ontario basin, including record precipitation in the April-May time frame, and above-average inflows from the upper Great Lakes. The widespread wet spring weather also led to record flows in May from the Ottawa River into the St. Lawrence River near Montreal and severe flooding conditions that extended further downstream.”

Throughout the spring, the board said it was faced with releasing water from a flooding Lake Ontario into a flooded St. Lawrence River.

“The events of 2017 once again demonstrate the vulnerability of shoreline communities to flooding and erosion. To reduce the risk of future damages, the most effective approach is to make property and infrastructure more resilient to coastal hazards and redouble efforts to prepare for future high water events.”