The Skeena River Estuary
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Morphodynamics of a Bedrock Confined Estuary and Delta: The Skeena River Estuary by Amanda Lily Wild B.Sc., University of Victoria, 2018 A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science In the Department of Geography ©Amanda Wild, 2020 University of Victoria All rights reserved. This thesis may not be reproduced in whole or in part, by photocopy or other means, without the permission of the author. Morphodynamics of a Bedrock Confined Estuary and Delta: The Skeena River Estuary By Amanda Lily Wild B.Sc., University of Victoria, 2018 Supervisory Committee Dr. Eva Kwoll, Co-Supervisor Department of Geography Dr. Gwyn Lintern, Co-Supervisor Natural Resources Canada ii Abstract Bedrock islands add variation to the estuarine system that results in deviations from typical unconfined estuarine sediment transport patterns. Limited literature exists regarding the dynamics of seabed morphology, delta formation, sediment divergence patterns, and sedimentary facies classifications of non-fjordic bedrock confined systems. Such knowledge is critical to address coastal management concerns adequately. This research presents insights from the Skeena Estuary, a macrotidal estuary in northwestern Canada with a high fluvial sediment input (21.2-25.5 Mtyr-1). Descriptions on sub-environments, stratification, and sediment accumulation within the Skeena Estuary utilize HydroTrend model outputs of riverine sediment and discharge, Natural Resources Canada radiocarbon-dated sediment cores and grain size samples, and acoustic Doppler current profiler and conductivity-temperature-depth measurements from three field campaigns. Research findings delineate a fragmented delta structure with elongated mudflats and select areas of slope instability. Variations from well-mixed water circulation to lateral stratification, govern the slack tide flow transition and sediment transport pathways within seaward and landward passages of the estuary. Fostering a comprehensive understanding of bedrock confined estuary and delta systems has implications for the assessment of coastal management strategies, the productivity of ecological habitats, and the impacts of climate change within coastal areas. iii Table of Contents Supervisory Committee ................................................................................................................................ ii Abstract ........................................................................................................................................................ iii Table of Contents ......................................................................................................................................... iv List of Tables ............................................................................................................................................. viii List of Figures .............................................................................................................................................. ix Frequent Abbreviations ................................................................................................................................ xi Acknowledgements ..................................................................................................................................... xii Dedication .................................................................................................................................................. xiii Introduction ................................................................................................................................................... 1 Literature Review on Estuaries ................................................................................................................. 2 Estuary Definition ................................................................................................................................. 2 Estuarine Processes ............................................................................................................................... 3 Estuarine Phenomenon .......................................................................................................................... 5 Estuarine Physiography and Features ................................................................................................. 15 Anthropogenic Impact on Estuaries .................................................................................................... 23 Skeena Background ................................................................................................................................ 25 Geographical Extent of the Skeena Estuary ........................................................................................ 25 Skeena River Hydrology ..................................................................................................................... 27 Skeena Basin Geology ........................................................................................................................ 31 Skeena in the Quaternary Period ......................................................................................................... 32 Skeena Estuary Hydrodynamics ......................................................................................................... 35 Skeena Estuary Seabed Morphology .................................................................................................. 37 Local Relevance of Sediment Load and Morphodynamics ................................................................ 39 Thesis Structure and Research Questions ............................................................................................... 41 Chapter 1: Skeena River Sediment Load and Discharge under Changing Climate .................................... 42 Introduction ............................................................................................................................................. 42 The HydroTrend Model .......................................................................................................................... 42 Methods .................................................................................................................................................. 44 HydroTrend Setup for the Skeena Watershed over a Historic Period (1981-2010) ............................ 44 Methods for using Different Climate Scenarios to Model into the Future (2010-2100) ..................... 46 HydroTrend 1981-2010 Validation ......................................................................................................... 49 GCMs vs ECCC Climate Station Climatographic Comparison .......................................................... 49 SB2 HydroTrend Results vs Usk Hydrometric Station ....................................................................... 52 iv SB1 HydroTrend Results (ECCC vs GCM Model Inputs) ................................................................. 56 Combined HydroTrend vs CTDTu & Water Sample SSC at the Tidally Drowned River Mouth ...... 56 HydroTrend Results ................................................................................................................................ 58 1981-2010 HydroTrend (ECCC Inputs) Outputs for the Entire Skeena Watershed ........................... 58 RCP 4.5 Scenario 30 Year 1981-2100 HydroTrend (GMC Inputs) Outputs ...................................... 61 RCP 8.5 Scenario 30 Year 1981-2100 HydroTrend (GMC Inputs) Outputs ...................................... 63 Impact of RCP 4.5 vs 8.5 on Climate Inputs & Subsequent HydroTrend Results .................................. 65 Discussion ............................................................................................................................................... 66 Skeena Sediment Load in Comparison to Past Estimates ................................................................... 66 Effect of Changing Sediment Load ..................................................................................................... 67 Additional Considerations................................................................................................................... 68 Chapter 2: Skeena Estuary and Delta Classification and Seabed Morphodynamics .................................. 70 Ch.2 Introduction .................................................................................................................................... 70 Data Collection and Preparation ............................................................................................................. 70 Bathymetry .......................................................................................................................................... 70 Seabed surface grab samples and sediment cores ............................................................................... 71 Water column data .............................................................................................................................. 72 Additional Data Sources ..................................................................................................................... 73 Results ..................................................................................................................................................... 73 Skeena River and Estuary Morphology .............................................................................................