Alluvial Floodplain Classification and Organization in Low-Relief Glacially Conditioned River Catchments by Roger Thomas James Phillips A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Department of Geography University of Toronto © Copyright by Roger Phillips, 2014 Alluvial Floodplain Classification and Organization in Low-Relief Glacially Conditioned River Catchments Roger Thomas James Phillips Doctor of Philosophy Department of Geography University of Toronto 2014 Abstract The imprint of late Pleistocene glaciation on river systems is an essential theme in Canadian geomorphology. Existing ideas about glacial legacy effects tend to focus on mountainous environments, which are different from the low‐relief physiography of the Laurentian Great Lakes region. This study investigates river landforms in southern Ontario to develop an improved conceptual fluvial landscape model, reflecting glacial legacy and post‐glacial fluvial processes. The analysis is based on an original dataset, including basic channel observations from over 500 field sites, alluvial floodplain properties from 109 sites, and published physiographic mapping from digital sources. Glacial signatures are evident in river profiles extracted from a digital elevation model (DEM) for 22 river catchments in southern Ontario. Stream power and slope–area analysis stratify river slopes by glacial landform types and demonstrate significant differences between rivers incised into glacial moraines versus plains. A stream length–gradient index provides a relative measure of how river profiles are oversteepened or understeepened by glacial landforms relative to a theoretical graded profile. ii Four first‐order alluvial floodplain classifications are presented using k‐means clustering analysis. Predictive variables are explored using PCA and discriminant analysis, producing two principal components: (1) stream power‐resistance and (2) floodplain sedimentology (or floodplain sand equivalent, FSE). The river classifications from this study are consistent with previous literature, but special consideration is required for the inherited sources of cobble and sand materials. General glacial–fluvial landform relationships can broadly be clustered into: 1) topographic and sedimentological glacial legacy effects; 2) landforms resulting from isostatic and lake baselevel change, and 3) superimposed patterns of Holocene fluvial sediment supply. The adapted fluvial landscape model and conceptual framework presented for rivers in low‐relief glacially conditioned landscapes have the potential to enhance interdisciplinary and applied science in the areas of biogeochemistry, geoarcheology, conservation ecology, and environmental water resources management. iii Acknowledgments It doesn’t hurt to start with your PhD supervisory committee. Joe Desloges, Sarah Finkelstein, Bill Gough, Brian Branfireun, and Nick Eyles, thank you greatly for all your academic and intellectual advice over the years. Joe, you have been an extraordinary mentor in science and teaching. I marvel at your work ethic and dedication to students. Sarah, your enthusiasm and thoughtfulness in teaching are inspiring; and thanks to you I will never forget counting diatoms under the microscope for hours in PGB. Bill, you may not have started as a geographer, but I very much admire your passion for geography now. Brian, our pre‐comps discussions of representative elementary areas were compelling and formative. Nick, our tour of southern Ontario geological sites in 2008 was invaluable to my learning. I am grateful to André Roy for his positive and constructive external review of this dissertation and for our insightful discussions during the thesis defense. Thanks also to Mike Church for reading parts of this thesis, and specifically for his review and comments on Chapter 3 resulting in considerable enhancements to the final thesis. Thanks to the many field assistants over the period of 2010–2013, namely Stephanie Mah, Beata Opalinska, and Joyce Arabian; as well as James Thayer, Jennifer Henshaw and Tina Hui who also donated some of their own field data. Thanks also to the many public agency staff from OMNR and Conservation Authorities who responded to our information requests, including Brynn Upsdell, Kari Jean, and Ross Wilson (ABCA); Peter Dragunas and Tony Difazio (CCCA); Shannon Wood and David Pybus (SVCA); Glenn Switzer (NVCA); Muriel Andreae and Rick Batterson (SCRCA); Joe Gordon and Brian Widner (KCCA); and Kent Todd (OMNR). iv This research was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC‐CGS graduate scholarship) and research funding from the University of Toronto to J.R. Desloges. Again to my patient PhD advisor Joe Desloges, my sincerest gratitude for your guidance and support over the last 6 years. As the saying goes, or it goes without saying, I could not have done this without you. The thesis might be a bit long, or I guess in the words of Mike Church, a bit overdone. So thank you for accepting a few literary indulgences. Oh well, my mother Doris never minded burnt toast. But she also said I could be rather verbose. I suppose she would be proud of me no matter what. Thanks mom. To my late father Reginald Phillips (1927–2013) I owe my perseverance for learning. To my wife Kate, thank you for your loving commitment, for your editorial reviews, and for remembering that Snuffbox has an “n” in the name. Dedication For Kate, Amelie, and Lachlan. Yes Amelie, I am done my work now. Can you find the three little book mice? v Table of Contents Abstract ............................................................................................................................................ ii Acknowledgments ........................................................................................................................... iv Table of Contents ............................................................................................................................ vi List of Tables ................................................................................................................................. viii List of Figures .................................................................................................................................. ix List of Appendices ........................................................................................................................... xi Chapter 1 Introduction ................................................................................................................... 1 Research Statement ................................................................................................................... 1 1.1 Glacial Legacy Effects on Fluvial Systems ........................................................................... 4 1.2 Fluvial Process and Landform Interactions ......................................................................... 9 1.3 The Laurentian Great Lakes Region .................................................................................. 17 1.3.1 Modern human impacts ....................................................................................... 21 1.4 Summary of Study Approach ............................................................................................ 21 1.4.1 Statement of authorship and publication status .................................................. 23 Chapter 2 Glacially conditioned specific stream powers in low‐relief river catchments of the southern Laurentian Great Lakes ............................................................................................. 24 2.1 Introduction ...................................................................................................................... 25 2.2 Theoretical Background .................................................................................................... 26 2.2.1 The graded river concept ...................................................................................... 26 2.2.2 Specific stream power approach .......................................................................... 30 2.3 Regional Setting ................................................................................................................ 33 2.4 Materials and Methods ..................................................................................................... 36 2.5 Specific Stream Power Inputs ........................................................................................... 41 2.5.1 Discharge regime models ...................................................................................... 41 2.5.2 Bankfull width regime models .............................................................................. 44 2.5.3 DEM longitudinal profile extraction and slope generalization ............................. 47 2.6 Results and Discussion ...................................................................................................... 51 2.6.1 Specific stream power mapping ........................................................................... 51 2.6.2 Profile analysis and SL/K index.............................................................................. 54 2.6.3 Slope–area analysis ............................................................................................... 59 2.6.4 Glacial conditioning of stream power ................................................................... 64 2.7 Conclusions