Protection of the banks of the Saint Lawrence River and auto-regeneration of a marsh at Rivière-du-Loup

Pilot project intended to solve the problem of erosion of the banks of the Saint Lawrence River along Autoroute 20, an entire segment of which is threatened due to significant erosion of the marsh separating the highway from the River. 

The Ministère des Transports du Québec wanted to implement protection measures to mitigate the erosion of the banks of the Saint Lawrence River in this sector to avoid destabilization of transportation infrastructure assets and promote auto-regeneration of the intertidal marsh, which has been destroyed over the course of the last 40 years. 

In order to meet the MTQ’s objectives, the project was executed in multiple phases. The first phase involved emergency stabilization of the most critical erosion zone along Autoroute 20 by installing riprap using 0-500 kg stone along the River over a distance of 130 metres. The second phase involved the design of an innovative “T” shaped protective installation 120 metres from the River, comprising a transverse levee intersecting the main breakwater, which measures 300 metres long and runs parallel to the River, constructed using 1- to 5-ton stones.  

Environmental protection 

The solution proposed by the team for resolving the complex erosion problem involved the construction of an innovative installation that is unique in Québec: a submersible breakwater with a perpendicular arm. This “T” shaped protective riprap installation allows for restoration of the marsh, recharging of the shore and planting of salt-water cord grass, thus creating a reserve habitat for fish.  

Award earned by the team 

This project received an Award from the Association des ingénieurs-conseils du Québec in the Environment category in 2012. 

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