Morphological and numerical modeling of a highly dynamic tidal inlet at Shippagan Gully, New Brunswick

Shippagan Gully is a highly engineered, tidal inlet located near Shippagan, New Brunswick, on the Gulf of St. Lawrence. It is a particularly complex tidal inlet due to the fact that its tidal lagoon transects the Acadian peninsula and is open to the Bay des Chaleurs at its opposite end. As such, two open boundaries with phase lagged tidal cycles drive flow through the inlet, alternating direction with each tide and reaching velocities exceeding 2 m/s. Over the past century, despite various engineered interventions, shipping practices through the inlet have been threatened due to the increasing constriction from sediment which has accumulated on the east side of the navigation channel. In addition to highly asymmetrical sediment deposition patterns, severe downdrift erosion suggests the presence of prominent westward net longshore transport, further complicating the coastal morphology at the inlet. Due to the overwhelming requirement for constant maintenance dredging and the long-term degradation of existing coastal structures, a numerical model study of Shippagan Gully has been undertaken in order to identify principal morphology mechanisms and provide guidance for future coastal works. The numerical models CMS Wave and CMS Flow (USACE) have been applied in a coupled manner to simulate the hydrodynamics, coastal processes and morphology changes at the inlet due to the combined effects of waves and tides. Once calibrated to historical morphologic evolution, the coupled models were used to identify the forces driving the morphological changes shaping Shippagan Gully. The methodology and selected results of this study are presented herein.
Annual Conference of the Canadian Society for Civil Engineering 2011, CSCE 2011, 14 June 2011 through 17 June 2011, Ottawa, ON