MODELLING COASTAL PROCESSES DRIVEN BY WINDS AND TIDES ACROSS A RANGE OF SPATIAL SCALES IN A MACROTIDAL BAY by Cody L. McLaughlin A thesis submitted to the Department of Civil Engineering In conformity with the requirements for the degree of Master of Applied Science Queen’s University Kingston, Ontario, Canada June, 2021 Copyright © Cody L. McLaughlin, 2021 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. ii Co-Authorship Significant contributions to this manuscript were made by Dr. Ryan Mulligan and Dr. Brent Law through direct supervision of work including interpretation of model results and commenting on the original work of Cody McLaughlin as well as aiding in data collection from site visits. Chapter 2 has been re-submitted after revisions to the Coastal Engineering Journal in a special issue on Tropical Cyclones: McLaughlin, C., Law, B., and Mulligan, R.P., Modelling surface waves and tide-surge interactions leading to enhanced total water levels in a macrotidal bay, Coastal Engineering Journal, submitted. The material contained in Chapter 3 will be submitted to a journal at a later date: McLaughlin, C., Law, B., and Mulligan, R.P, Modelling spatial and temporal variability in tidal currents and bed shear stress at a macrotidal salt marsh channel and mudflat, in preparation for submission to Coastal Engineering. iii Acknowledgements I would like to thank my supervisors Ryan Mulligan and Brent Law for all the help that have given me in the pursuit of finishing my thesis. Thank you Ryan for the constant support and unwavering patience, you are the reason I am where I am today and I am forever grateful. Thank you Brent for taking me on during the site visits in Kingsport. The field knowledge I gained is almost as invaluable as the rib recipe you gave me. I would like to thank Tim Milligan (DFO), Paul Hill (Dalhousie), Danika van Proosdij (Saint Mary’s), Casey O’Laughlin (DFO), Vanessa Zions (DFO), Alexander Rey (Queen’s), Kelsey McLaughlin (Mount Sinai) and Daniel Mutton (Acadia) for helpful scientific discussions. I would also like to thank my mom, dad, sisters and all my extended cousins and family who, along with my closest friends, provided me with the emotional support I needed to be able to complete this thesis. The model results used in this research are archived in the Department of Civil Engineering at Queen’s University and will be made available upon request. Funding for the research has been provided by Fisheries and Oceans Canada in the form of a Strategic Program for Ecosystem-based Research and Advice (SPERA) project grant to BAL and RPM, and we also acknowledge support from the Natural Science and Engineering Research Council of Canada (NSERC) Discovery Grant to RPM (RGPIN/04043‐2018). iv Table of Contents Abstract ......................................................................................................................................................... ii Co-Authorship.............................................................................................................................................. iii Acknowledgements ...................................................................................................................................... iv List of Figures ............................................................................................................................................. vii List of Tables ............................................................................................................................................... xi Chapter 1 Introduction .................................................................................................................................. 1 1.1 Background and Motivation................................................................................................................ 1 1.2 Importance of Research ...................................................................................................................... 2 1.3 Thesis Objective and Outline .............................................................................................................. 3 Chapter 2 Modelling surface waves and tide-surge interactions leading to enhanced water levels in a macrotidal bay ............................................................................................................................................... 7 Abstract ..................................................................................................................................................... 7 2.1 Introduction ......................................................................................................................................... 8 2.2 Observation ....................................................................................................................................... 11 2.2.1 The Gulf of Maine and Bay of Fundy System ............................................................................. 11 2.2.2 Hurricane Arthur (2014) ............................................................................................................ 12 2.2.3 Rapid Refresh Model (RAP) Wind Model .................................................................................. 13 2.3 Coupled Numerical Model ................................................................................................................ 14 2.3.1 Flow Model ................................................................................................................................ 14 2.3.2 Wave Model ............................................................................................................................... 15 2.4 Model Results ................................................................................................................................... 17 2.4.1 Wave Hindcast ........................................................................................................................... 17 2.4.2 Water Level Hindcast ................................................................................................................. 19 2.4.3 Storm Surge Hindcast ................................................................................................................ 20 2.5 The Saxby Gale (1869) ..................................................................................................................... 21 2.6 Combining Storm Surges and Tides ................................................................................................. 24 2.7 Summary and Conclusions................................................................................................................ 27 Chapter 3 ..................................................................................................................................................... 44 Modelling spatial and temporal variability in tidal currents and bed shear stress at a macrotidal salt marsh channel and mudflat .................................................................................................................................... 44 Abstract ..................................................................................................................................................