Acquiring knowledge on the sediment dynamics of Rivière à Mars for the sustainability of Atlantic salmon

The Rivière à Mars was greatly affected by the flood waters of July 1996. The flooding event created a profound imbalance in the system through an alteration of river dynamics during the flood and then by the large-scale riprapping carried out in response to the damage caused by the flood. Riprap disconnects a river from its margins and reduces the sediment supply required for hydrogeomorphic processes (HGM) and ecosystem services. As a result, Atlantic salmon habitat is greatly altered and leads to declining salmon populations. Every year, the organization Contact-Nature expends a great deal of effort, at great cost, to counteract the resulting problems; however, their actions have yet to bear fruit.

This project implements an innovative strategy to restore HGM processes to sustainably re-establish Atlantic salmon habitat in the first ten kilometres of the Rivière à Mars upstream from its entrance into the Baie des Ha!Ha!.

The overall aim of this research is to characterize the sediment transport dynamics in the Rivière à Mars to restore hydrogeomorphological processes and define the river’s mobility space prior to any riprap removal. This research has three specific methodological objectives:

1. Analysis of the historical trajectory of the Rivière à Mars using airborne imagery obtained since 1950.
2. Analysis of sediment dynamics though an interannual morphological monitoring of 64 transects installed at regular intervals along the river and a monitoring system comprising passive and active transponders (Pit-Tag RFID) to assess sediment transport distance according to granulometric size and flood amplitude.
3. Defining of a mobility space for the river, taking into account civil security issues.

This project is co-directed by Thomas Buffin-Bélanger (UQAR).