Posted at 10:00 a.m.
Îles-de-la-Madeleine, November 2018. Several storms hit the coast, with winds of up to 130 km/h and powerful waves that engulfed meters of beach.
“The lower the level of the beaches, the more the energy of the waves of the following storms creates damage”, explains Mathieu Leclerc, civil engineer and team leader of the natural hazards and adaptation to climate change module of the general management. du Bas-Saint-Laurent–Gaspésie–Îles-de-la-Madeleine to the Ministère des Transports.
PHOTO PROVIDED BY THE MINISTRY OF TRANSPORTS OF QUEBEC
On November 28 and 29, 2018, a storm caused the dune to retreat by nearly 15 m. A shovel does a minimal job of protecting the bank during the storm.
Long term solutions
This is what happened in the area of Route 199 which runs along the village of Pointe-aux-Loups. “For several kilometres, the road is built on a vegetated dune on both sides, but the storms of 2018 caused submersion,” said Mr. Leclerc.
In the urgency to act, a riprap was made in 2019 on a portion of a hundred meters. Then, rip rap work was carried out in 2021 to protect a 1.2 km section of the road. “But riprap is not the ideal solution on a beach,” says the engineer. It is rather necessary to recreate the natural environment, therefore to carry out a beach replenishment. »
Normally, the beach erodes with storms and subsequently recharges naturally, but when the infrastructure is too close to the water, the process does not have time to occur before damage is done.
Mathieu Leclerc, civil engineer
One of the challenges is the amount of sand needed to recharge the beach at Pointe-aux-Loups. “We need 900,000 m3 to silt up 5 km, he says. It’s astronomical! And it takes natural sand. So we have to innovate. »
Several strategies are studied. In particular, a project is planned for 2023 to recover 100,000 m3 of sand from the dredging carried out for the passage of boats in the channel and which is generally discharged into the open sea. This recovered sand will then be used to replenish the beach. “We have already carried out small projects of this kind, for 5,000 or 10,000 m3but it will be our first large-scale project,” says Mr. Leclerc.
PHOTO PROVIDED BY THE MINISTRY OF TRANSPORTS OF QUEBEC
We see here the riprap of 140 m (under construction).
Trying to predict the future
Damage caused by natural hazards is no longer a surprise. The Department of Transportation has been tracking climate change since the 2000s.
We are changing our calculation standards, for example by amplifying the flow of rivers which is caused by the multiplication of strong storms of short duration, to assess the impacts on our structures and infrastructures.
Sophie St-Jacques, Civil Engineer and Director of Hydraulics at the Ministry of Transport
Data on water levels in rivers during spring floods and wave heights reached during storms are collected in order to then make models and thus assess the submersion and erosion of the banks.
“We do these assessments for the short term in order to plan the work that will have to be done urgently,” explains Ms.me St Jacques. These assessments also allow us to trace long-term trends to ensure that our infrastructures have a long enough life expectancy. »
PHOTO PROVIDED BY THE MINISTRY OF TRANSPORTS OF QUEBEC
We see what the bank looked like on December 19, 2018 with the small rockfills that were made urgently.
An element to follow closely: the ice cover on the river. “The ice protects the coasts, but it comes later and later in the winter and disappears earlier and earlier, so the damage increases,” she says.
How well will we be able to play against the forces of nature? Wouldn’t it be better to move infrastructure away from waterways? “It’s a question we constantly ask ourselves, concedes Mathieu Leclerc. It is sometimes possible to move roads, for example on the North Shore where there is space. It’s more difficult in the Gaspé because people are settled along the road. But, one thing is certain, the impacts of climate change are only beginning to be felt, so we will have to continue to adapt. »