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The Character of Channel Planform Control on the Morphology And THE CHARACTER OF CHANNEL PLANFORM CONTROL ON THE MORPHOLOGY AND SEDIMENTOLOGY OF THE GRAVEL-BED SQUAMISH RIVER FLOODPLAIN, BRITISH COLUMBIA GARY J. BRIERLEY B.A.(Hons), Durham University, 1981 M.Sc., Simon Fraser University, 1984 THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in the Department of Geography 0 GARY J. BRIERLEY 1989 SIMON FRASER UNIVERSITY February, 1989 All rights reserved. This work may not be reproduced in whole or in part, by photocopy or other means, without permission of the author. APPRWAL Name : Gary John Brierley Degree: Doctor of Philosophy Title of Thesis: The Character of Channel Planfom Control on the Morphology and Sedimentology of the Gravel-Bed Squamish River Floodplainr British Columbia Examining Cmittee: Chairman: J.T. Pierce Associate Professor E.J. Hickin Professor Senior Supervisor M.C. Roberts Professor -- -- 7 --* A.D. Miall Professor Department of Geology University of Toronto / V -.-. -. - i -- - / D.G. Sith Professor External Examiner Department of Geography University of Calgary PART IAL COPYR l GHT L I CENSE I hereby grant to Simon Fraser Unlverslty the right to lend my thesis, proJect or extended essay (the title of which is shown below) to users of the Simon Fraser University Library, and to make partial or single copies only for such users or In response to a request from the library of any other unlverslty, or other educatlonal institution, on its own behalf or for one of Its users. I further agree that permission for multiple copying of this work for scholarly purposes may be granted by me or the Dean of Graduate Studies. It is understood that copying or publication of this work for flnanclal galn shall not be allowed without my written permission. T i t 1 e of Thes i s/Project/Extended Essay The Character of Channel Planform Control on the Morphology and Sedimentology of the Gravel-Bed Squamish River Floodplain, ' British Columbia Author: . .-.. .- (sign$ture) Gary John Brierley April 7, 1989 (date) ABSTRACT The gravel based, high energy Squamish River exhibits a distinct downstream sequence of river channel planform styles. In the 20km study reach, the river changes from a braided through a wandering gravel-bed to a meandering planform type. To assess the sedimentologic distinctiveness of these planform styles, sediment sequences were examined in a series of holes, regularly spaced in a grid-like fashion on 10 channel bar surfaces, in 9 trenches, dug perpendicular to the main channel at the barlfloodplain margin of 5 bars, and in 13 longitudinal bank exposures, divided equally among the three planform styles. A specific facies coding scheme was developed, based on channel bedform features. An alternative, broader scale depositional unit (termed elements), based on geomorphic criteria, also was employed in the trench and bank exposure data sets. Sedimentologic differentiation of the three channel planform styles was examined in terms of facies and element abundance, their composition and character, their spatial organization (vertically, laterally and longitudinally), particle size trends, and basal surface characteristics. Markov-derived planform facies models indicate complex sediment associations in each planform reach. Observed differences between models are largely insignificant and sediment trends relate much more closely to local depositional environment (or locales, namely bar platform, chute channel, ridge and established floodplain) than to channel bar type, or channel planform style. Locale spatial association varies by planform, but this variability is not reflected in floodplain deposits, as channel bar sediments are reworked by chute channels prior to being incorporated into the floodplain (i.e. bar platform deposits have extremely low preservation potentials). In both the trench and bank exposure data sets, facies are extremely laterally discontinuous, and vertical, sediment sequences typically are characterized by upward transitions from channel framework gravels to lower energy depositional units, irrespective of channel planform type. When analysed in vertical sequence, locale type is evaluated in elemental terms. The established floodplain locale is divided into flood cycle and sand sheet elements. These vertically accreted, top stratum deposits, are the dominant component of the Squamish River floodplain. In the older sediment sequences of bank exposures, distal overbank deposits occasionally are observed. In these instances, the preserved proportion of bar platform (bottom stratum) sands is greater, as chute channel reworking of sediments is minimized by rapid shifting or avulsion of the main channel. When based on small scale sediment structures, facies types and their organization can not be used to differentiate between river depositional environments, as they merely reflect local scale flow conditions. Similarly, as there is no process differentiation between planform types, river channel planform style can not be detected from sediment patterns. In contrast, the element scale, based upon field geomorphic units, provides much more insight into environment of deposition, and offers greater reliability in past environmental reconstruction. ACKNOWLEDGEMENTS This thesis could not have been completed without the digging efforts of many graduate colleagues and friends. Thanks are especially extended to my summer field assistants, namely John Olyslager, Rod Malcolm, Kelly Thompson and Graham Schnare. The Eluck cabin, along with hospitality from Sue and Marty Vanderhoof, made the Upper Squamish experience much easier and more enjoyable than it might otherwise have been. Computing assistance for Markov Analysis was provided by Eddie Leung. The intellectual stimulation and financial support for this study were supplied by Professor Edward Hickin (and his NSERC grant). Thanks Ted, for help during the many ups and downs of this project. Thanks also to the other members of my supervisory/examining committee, for their advice and comments. TABLE OF CONTENTS Approval ...................................................................................................................................ii ... Abstract ...................................................................................................................................ill Acknowledgements ....................................................................................................................v List of Tables ...........................................................................................................................xi List of Figures ........................................................................................................................xiv A. FRAMEWORK OF THE STUDY ....................................................................................1 I . INTRODUCTION .................................................................................................2 1 : 1 Introductory statement ..................................................................................2 1 : 2 Objectives .....................................................................................................2 1 : 3 Outline and organization of the study .............................................................3 I1. LITERATURE REVIEW .......................................................................................5 2 : 1 Introduction and outline of chapter .................................................................5 2 : 2 River classification and geomorphic controls upon channel planform style ........ 5 2 : 3 Floodplain geomorphology ..............................................................................9 2 : 4 : 1 Introduction to fluvial sedimentology .......................................................11 2 : 4 : 2 The facies concept and facies modelling principles ....................................13 2 : 5 : 1 Channel bar sedimentology .....................................................................14 2 : 5 : 2 River floodplain sedimentologic zones ......................................................16 2 : 6 : 1 Sedimentology of braided river reaches ....................................................16 2 : 6 : 2 Sedimentology of wandering gravel-bed river reaches ..............................19 2 : 6 : 3 Sedimentology of meandering reaches .....................................................21 2 : 6 : 4 Sedimentologic differentiation of channel planforms .................................23 2 : 7 Architectural element analysis .....................................................................27 2 : 8 The state of the art ......................................................................................28 I11. REGIONAL SETTING ........................................................................................29 3 : 1 Introduction ................................................................................................29 3 : 2 Geologic Background ...................................................................................29 3 : 3 Recent glacial history and its consequences ..................................................31 3 : 4 Climate, hydrology and other physical factors .............................................. 31 3 : 5 :1 Geomorphology of the Squamish River Basin : Introduction ......................32 3 : 5 : 2 Howe Sound fjord and the Squamish River delta ......................................34 3 : 5 : 3 Sediment sources within the Squamish
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