Abstract Lake Saint-Francois is a fluvial lake of the St. Lawrence system which is used for hydropower production and commercial navigation. For 150 years, it was dredged and dammed regularly without any impact analysis being made. The cumulative impact of dredging and damming on large rivers such as the St. Lawrence is an issue with only qualitative answers. Bidimensional hydrodynamics was used to simulate ancient flow conditions and to produce quantitative descriptors. These two NFMs were compared, showing important changes in the morphology of the lake.
Results highlight the cumulative physical transformation of the system.
These hydrodynamic transformations had a definitive impact on sedimentation and most probably on aquatic plans distribution.