Hydrodynamic and Morphologic Modelling of Alternative Design Scenarios Using CMS: Shippagan Gully, New Brunswick.

摘要

There is a highly dynamic tidal inlet known as Shippagan Gully located on the Gulf of St-Lawrence near Le Goulet, New Brunswick. This tidal inlet is highly unusual due to the fact that the inlet is part of a waterway that transects the Acadian Penninsula, connecting the Bay de Chaleurs and the Gulf of St- Lawrence. Thus, the inlet has two open boundaries with phase lagged tidal cycles that drives flow through the inlet. The phase lag in the tidal cycles causes an imbalance in the flood and ebb flows, which leads to an ebb flow twice as strong as the flood flow. Over the past few decades the shipping activities through the inlet have been threatened due to the narrowing of the navigation channel caused by deposited sediment on the east side of the channel. Many engineering projects have been undertaken at Shippagan Gully in order to try and mitigate the deposition problem. However, these attempts have either been unsuccessful or the engineered structures have deteriorated over the years.;A second numerical model, GenCade, was employed to model the potential shoreline change downdrift (south-west) of the inlet due to the addition of a sediment trapping structure. The model was calibrated to net longshore sediment transport rates obtained through the Kamphuis (1991) and CERC (1984) longshore transport equations. The calibrated GenCade model was used to make educated conclusions on any potential changes downdrift of the inlet.;The research described herein contributes towards an improved understanding of the hydrodynamics and sedimentary processes at Shippagan Gully. Moreover, the results presented herein can be used to help select an optimal approach for stabilizing and widening the channel through the inlet mouth in order to improve navigability and increase navigation safety. This thesis was completed in partnership with NRC Ocean, Coastal and River Engineering (NRC-OCRE) and with funding provided in part by Public Works and Government Services Canada (PWGSC).;This study uses a numerical model that is based on coupling the most recent CSM-Flow and CMSWave models developed by the US Army Corps of Engineers. The numerical model was used to provide guidance concerning the response of the inlet to various potential interventions aimed at improving navigation safety. The development of the model and the methodology followed to calibrate and validate it against field measurements from the site is described. The coupled numerical model is capable of simulating the depth-averaged currents generated within Shippagan Gully and along the neighbouring coastline due to the effects of tides, winds and waves; the transport of non-cohesive sediments; and the resulting changes in seabed morphology. Once the model was calibrated and validated to a reasonable precision, the model was applied to investigate coastal processes for the existing conditions of the inlet and for twenty-one alternative future scenarios (inlet configurations).