Ottawa River flooding has come in waves before
Near back-to-back flooding last seen in 1974, 1976
It's been a while, but this isn't the first time the Ottawa River has seen near back-to-back floods.
As of Tuesday morning, the Ottawa River was flowing at a rate of 7,700 cubic metres per second at the Carillon Dam, just downstream of Hawkesbury, Ont.
- Spring melt means worst flooding could yet be to come
- The latest flood-related road closures and detours
- Flooding in Pontiac to peak Saturday, officials say
It's flowed at that rate or higher in the Hawkesbury area only eight other times since 1900, according to data provided by the Ottawa River Regulation Secretariat:
- 2017: The highest flow recorded since 1900, at 9,100 cubic metres per second.
- 1976: 8,200 cubic metres per second.
- 1974: 8,100 cubic metres per second.
- 1951: 8,300 cubic metres per second (river flow prior to 1962 was measured elsewhere in the Hawkesbury area, as the Carillon Dam was not yet built).
- 1947: 8,175 cubic metres per second.
- 1928: 8,760 cubic metres per second.
- 1909: 8,400 cubic metres per second.
Similarly to this year and 2017, the river saw high flows in both 1974 and 1976.
These high Ottawa River flows don't always result in the same flooding patterns, however. The flow out of the Gatineau River might be particularly high one year, affecting nearby communities more than others.
"There are all kinds of variables that go into it. But in general, when it's that high, everybody's having trouble, everybody's seen flooding," said Ottawa River Regulation Secretariat senior regulation engineer Michael Sarich.