Preliminary evaluation of impacts of sand extraction near Iles-de-la-Madeleine Archipelago, Québec, Canada

This paper assesses the potential sedimentological impacts of an inner-shelf sand extraction project near the I1es-de-la-Madeleine archipelago in the central Gulf of St. Lawrence. Commercial extraction of nearshore aggregates is a growing industry around the world, but sound techniques to evaluate its impacts on local physical environment are still scarce. A review of the potential impacts is first presented, based mainly on European experience. Criteria related to impacts, developed for conditions prevailing in the North Sea or in the Gulf of Gascogne (France) are adapted to meet the more moderate hydrodynamic and sedimentologic conditions of the Gulf of St. Lawrence. It is found that modifications to the wave refraction patterns due to bathymetry changes is the dominant criterion here. Excavations are then designed to limit these modifications in such a way as the resulting littoral drift changes are kept within bound specified after the local sediment budget.