MODELLING COASTAL PROCESSES DRIVEN BY WINDS AND TIDES ACROSS A RANGE OF SPATIAL SCALES IN A MACROTIDAL BAY
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Date
Authors
Mclaughlin, Cody
Keyword
storm surge , waves , coastal wetland , hurricane winds , Bay of Fundy , Gulf of Maine , Delft3D , currents , intertidal marsh , morphology , bed shear stress
Abstract
The Bay of Fundy system in the Atlantic Ocean is a highly dynamic environment characterized by the highest tidal range in the world. The area contains a wide range of coastal environments and structures including salt marshes and protective dyke systems. These systems are at risk of being altered due to future climate change, with likely increases in mean sea level and storm intensity, and proposed installation of in-stream tidal power extraction devices. To assess the vulnerability of the Bay of Fundy to hazards, large-scale and small-scale investigations are completed using available field observations and the hydrodynamic model Delft3D. The large-scale investigation composed of examining the effects of hurricane induced storm surge in the Gulf of Maine and Bay of Fundy using a depth-averaged model and two connected model grids. Hurricane Arthur (2014) is used as a test storm to validate the model before varying input conditions were used including modelling the Saxby Gale of 1869, a devastating storm that impacted the Bay of Fundy. Model results suggest that the combined effects of wind driven waves and storm surge could overtop dyke systems in the Minas Basin if the storm coincides with the high tide of a perigean spring tide. The small-scale investigation is focused on Kingsport Marsh, Nova Scotia, an intertidal salt marsh in the Minas Basin, using a three-dimensional model and four connected model grids with increasing resolution. The goal of this study is to gain insight to the hydrodynamics and morphology of the marsh channels and mudflats. Observational results over a 7-year time period suggest that the bed is slowly accreting in the marsh and that the networks of creek channels are migrating. Model results are validated at the two instrument sites and the model is used to spatially analyze the intertidal hydrodynamics. Spatial model results display a dynamic environment during the flood and ebb tides with bed shear stresses sufficient to initiate sediment resuspension. Overall, this research contributed to a better understanding of the coastal processes in a highly dynamic macrotidal environment, by aiding in the understanding of the complexity of tidal marsh environments as well as assessing the risk involved in storm surge interactions to local dyke systems, needed to accurately predict future responses to storms, climate change and proposed infrastructure development.