Published at 2:18 am. Updated at 7:00 a.m.
Could a major dam fail in Quebec as rainfall increases due to climate change?
Serge Loiselle
“This is highly unlikely,” says Jean-Luc Martel, a professor at the École de Technologie Supérieure, who served on the advisory committee for a report on the topic published by Ouranos in summer 2022. “The law on dam safety was tightened” after the Saguenay flood in 1996. These new standards affect the design of dams and existing dams. »
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Jean Luc Martel
Roughly speaking, dams must be able to withstand floods that occur once in 10,000 years without major damage. A disaster should only be possible if a flood occurs “every 100,000 years or 1 million years,” Mr. Martel says. If necessary, the capacity to release excess water from a dam could be increased to meet more stringent standards.
Recent high-profile floods, such as those of 2017 and 2019, were theoretically once-in-100-year events, according to Martel.
In 2022, the tightening of the dam safety law has led the Federation of Quebec Municipalities to apply for public funding to repair thousands of municipal dams in the province. The Government of Quebec’s financial assistance program for the modernization of municipal dams supported the modernization of 55 dams in 43 municipalities for a total of 6.7 million.
Won’t climate change significantly increase precipitation? “In Quebec, floods are mainly linked to spring snowmelt,” argues Mr. Martel. With climate change we should have milder and shorter winters and therefore less snow. If it rains a lot in summer or winter, that doesn’t change much. »
What happens if it snows more in the northern regions? “It could increase flooding,” Mr. Martel said. Perhaps the flood that currently only occurs once every 10,000 years will occur once every 9,000 years. It remains very unlikely and very extraordinary. »
The July 1996 floods in Saguenay reached levels that theoretically only occur once in 10,000 years. However, there is great uncertainty about this number. “Trying to estimate an event that occurs on average every 10,000 years based on about fifty years of observation is not an easy task. It is unlikely that we have observed such a rare event in such a short period of time. Therefore, such an estimate should normally be accompanied by a confidence interval. »
PHOTO RICARDO GARCIA VILANOVA, ARCHIVE ASSOCIATED PRESS
Floods have brought death and devastation in Derna, Libya.
The Derna dams in Libya, which collapsed in September after the passage of a Mediterranean hurricane, were poorly maintained, a Crisis Group report reported in October. This tragedy killed 20,000 people.
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275 mm of rain that fell in Saguenay from July 19 to 21, 1996
Source: BAPE