Analysis and modelling of the multiple responses of the Ste-Marguerite River to large-scale meander rectification

• Main Author: Talbot, Tracey D.
• Other Authors: Lapointe, Michel (advisor)
• Format: Others
• Language: en
• Published: McGill University 2000
• Subjects: Meandering rivers > Regulation > Québec (Province) > Saguenay-Lac-Saint-Jean Region.; Sainte-Marguerite River (Québec) > Regulation.; Sainte-Marguerite River (Québec) > Channels.
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30751

Early 1960's meander rectification of the Ste-Marguerite River, Quebec, Canada, was undertaken in order to facilitate highway construction along the valley bottom. Through analysis of thalweg elevation and grain size data, the fourfold response of the river since rectification has been determined: (1) 1 m of bed incision in the upper 4 km and 2m of bed aggradation in the lower 2 km of the 6 km straightened reach; (2) coarsening (up to 20 mm) of the pavement D50 and D84 in the area of maximum degradation; (3) lateral erosion of the channel into three high terraces; and (4) regrowth of three meanders within the reach. === Estimations indicate that reprofiling and pavement coarsening have been most important in reducing the disequilibrium in gravel transport rates due to rectification. Model simulations of the response to rectification have been validated against field data and the half-time scale of response has been estimated at 10 years. A further 10 cm of degradation upstream, 17 cm of aggradation downstream and 10 mm of pavement coarsening is predicted for the next century.