DOCSLIB.ORG

A Tentative Classification of Alluvial River Channels

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A Tentative Classification of Alluvial River Channels A Tentative Classification of Alluvial River Channels A Tentative Classification of Alluvial River Channels By S. A. Schumm An examination of similarities and differences among some Great Plains rivers GEOLOGICAL SURVEY CIRCULAR 477 Washington J 963 United States Department of the Interior STEW ART L. UDALL, SECRETARY Geological Survey THOMAS B. NOLAN, DIRECTOR Free on application to the U.S. Geological Survey, Washington 25, D. C. CONTENTS Page Page ~Abstract---------------------------- 1 The independent variables--Continued Introduction_________________________ 1 The importance of sediment type____ 3 The independent variables _ _ _ _ _ _ _ _ _ _ _ _ 1 A relation of percent silt -clay to Restrictions _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 bedload percent----------------- 6 The classification _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 7 Discharge ------------------------ 2 Total sediment load________________ 2 Conclusions_____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 7 Channel stability _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 References cited ______________ - _ _ _ _ _ 9 Mode of sediment transport_________ 2 ILLUSTRATIONS Page Figure 1. Relation of width -depth ratio to silt -clay_____________________________________ 4 2. Relation of sinuosity to width-depth ratio------------------------------------ 5 3. Relation of sinuosity to silt-claY-------------------------------------------- 5 4. Hypothetical relation of bedload to silt -clay__________________________________ 6 TABLE Page Table 1. Classification of alluvial channels____________________________________________ 8 III A Tentative Classification of Alluvial River Channels By S. A. Schumm ABSTRACT development in the cycle of erosion, such as .youthful, mature, and old (Davis, 1889), and A classification of river channels might be based on the independent variables, discharge and sediment load. Dis­ also according to their origin on a land sur­ charge, however, because it determines mainly the size of a face, such as antecedent, superposed, and channel, is not a critical factor for purposes of this study. consequent (Davis, 1890). These classifica­ Sediment load, because of its influence in determining chan­ nel stability, shape, and sinuosity, is used as the basis of tions relate the rivers to the geology of an this classification. Three classes of channels, stable, erod­ area and are used in the geologic interpreta­ ing, and depositing, are established with regard to channel tion of aerial photographs (Miller, 1962, p. 90- stability or the relation of sediment load to transportability. 97). The numerical classification of Horton A negative exponential correlation between silt-clay in (1945), whereby order numbers are assigned the stream channel and the percent of total sediment load transported as bedload is proposed. From this relation the· to the components of a drainage network, is limits of three additional classes of channels, bedload extremely useful in the morphometric analy­ mixed-load, and suspended-load, are established, on th~ sis of drainage systems. None of the above basis of the predominant mode of sediment transport or the proportions of suspended load and bedload transported ·classifications, however, gives an indication through a channel. "In all, nine subclasses of river channels of the character of the river channel with re­ are defined on the basis of channel stability and the dominant spect to the two independent variables, dis­ mode of sediment transport. charge and sediment load, upon which the INTRODUCTION n1orphology of alluvial river channels de­ pends. Classifications of natural phenomena are of value because they focus attention on the Melton (1936) related streams to the man­ key factors which distinguish the individual ner in which they build their flood plains, but phenomena. Conversely, they may tend to discharge and sediment load of the streams restrict thoughtful consideration of a prob­ did not determine Melton's classification­ lem by categorizing things which are really rather they were reflected in it. Owing to the members of a continuous series. When this complexity of the relationships and the lack disadvantage is recognized, they may become of data, it is not surprising that a classifica­ useful guides to further research. tion of river channels has not been attempted previously. This report classifies some relationships between river morphology and sediment type. THE INDEPENDENT VARIABLES The classification was prepared as a means of organizing these relationships as a guide RESTRICTIONS and stimulus to further research on the influ­ ence of sediment load on fluvial morphology. The proposals must be restricted in appli­ cation, first, because they are based on data Drainage patterns have been defined by obtained ·and observations made in the west­ geologists with regard to the respons~ of ern United States, mainly on the Great Plains, streams to geologic structure and lithology though the writer is hopeful that the relation­ of an area-for example, dendritic, rectangu­ ships may prove to be of a general nature; sec­ lar, and radial (Zernitz, 1932). Rivers have ond, the rivers studies are alluvial, generally been classified according to their stage of 1 2 A TENTATIVE CLASSIFICATION OF ALLUVIAL RIVER. CHANNELS having a well formed flood plain and lacking TOTAL SEDIMENT LOAD regulation of course or gradient by rock out­ crops except over short distances; third, the CHANNEL STABILITY channels contain less than 20 percent coarse gravel and the sediment load is, therefore, A major division of alluvial channels can relatively fine -grained. be made on the basis of stream stability or lack of it. These differences can be thought The classification can only be applied lo­ of with respect to the total sediment load de­ cally or to segments of a river system, for livered to the channel. An excess of total the characteristics of a stream channel can load causes deposition, a deficiency causes change significantly within a short distance erosion, and between the extremes lies the if it becomes unstable (Schumm, 1961) or re­ stable channel. Although often in the field ceives sediment of a different type from a a given river channel cannot be clearly iden­ tributary (Schumm, 1960a). Therefore, it is a tified as stable, eroding, or depositing, it is classification of channels rather than rivers. possible to think of all rivers as falling into one or another of these three classes. The classification, as indicated in the title, is tentative, for the basic data necessary to The stable channel is one that shows no prove its validity are lacking. Nevertheless, progressive change in gradient, dimensions, it is presented as a stimulus to the collection or shape. Temporary changes occur during of the necessary data and perhaps as ::~ new floods, but the stable channel, if the classifi­ approach to the consideration of alluvial cation were not restricted to short segments rivers. of the river, would be identical to the graded stream as defined by Mackin (1948) in which, DISCHARGE "over a period of years, slope is delicately adjusted to provide, with available discharge Discharge is an independent variable that and with prevailing channel characteristics, largely determin~s the size of stream chan­ just the velocity required for the transporta­ nels (Leopold and Maddock, 1953) and the am­ tion of the load supplied from the drainage plitude and wave length of meanders (Leopold basin." and Wolman, 195 ... ). Width and depth of the channels to be Jiscussed herein are largely a The eroding channel is one that is being function of dis..;harge, although the sediment progressively degraded or widened by bank forming the channel may introduce important erosion or both. Conversely, the depositing modifications (Schumm, 1962). channel is one that is being aggraded or is having sediment deposited on its banks or Discharge, however, is not a valid basis for both. Classification of river channels on the a classification of ~tream channels unless basis of stability as eroding, stable, or de­ size is considered most important, though a positing, emphasizes the diversity among qualitative distinction among stream channels rivers and stream channels; each of the three can be made on the basis of discharge char­ classes can be considered to be distinct from acteristics, that is, ephemeral and perennial the others. streams. This distinction is obvious but not fundamental. Dowr.stream differences be­ MODE OF SEDIMENT TRANSPORT tween ephemeral ctnd perennial streams have been d(:~monstrated by Leopold and Miller The channels are further subdivided with ( 19 56), but the ,. uthor has shown that some reference to the predominant mode of sedi­ elements of the pattern and shape of both ment transport through the channel. Mode of ephem,eral and perennial stream channels are transport is simplified here to mean the related to the type of sediment forming the transportation of sediment as either sus­ perimeter of the channel (Schumm, 1960a, pended load or bedload. 1963) rather than to the amount or character of discharge. THE INDEPENDENT VARIABLES 3 It is necessary to clarify the definition of c:omprises the bedload when the river is in the terms bedload and suspended load as used flood. The 0.351-mm size, because it re­ herein. According to Einstein, Anderson and flects flood conditions, seems too high, for Johnson (1940, p. 632) "the bed-load consists at low flows sediment particles 0.3 mm in of material moving as surface -creep and diameter will certainly move on the stream material moving in suspension, both of which bed. Sundborg (1956, p. 219) suggested that can be expressed as a rate related to the the finest material transported as bedload stream discharge. ****Primarily the con­ ranges from 0.15 to 0.20 mm, and Hjulstrom's ception is that bed-load and suspended load curves (1935, p.
Load more

Recommended publications
  • Measurement of Bedload Transport in Sand-Bed Rivers: a Look at Two Indirect Sampling Methods
    Published online in 2010 as part of U.S. Geological Survey Scientific Investigations Report 2010-5091. Measurement of Bedload Transport in Sand-Bed Rivers: A Look at Two Indirect Sampling Methods Robert R. Holmes, Jr. U.S. Geological Survey, Rolla, Missouri, United States. Abstract Sand-bed rivers present unique challenges to accurate measurement of the bedload transport rate using the traditional direct sampling methods of direct traps (for example the Helley-Smith bedload sampler). The two major issues are: 1) over sampling of sand transport caused by “mining” of sand due to the flow disturbance induced by the presence of the sampler and 2) clogging of the mesh bag with sand particles reducing the hydraulic efficiency of the sampler. Indirect measurement methods hold promise in that unlike direct methods, no transport-altering flow disturbance near the bed occurs. The bedform velocimetry method utilizes a measure of the bedform geometry and the speed of bedform translation to estimate the bedload transport through mass balance. The bedform velocimetry method is readily applied for the estimation of bedload transport in large sand-bed rivers so long as prominent bedforms are present and the streamflow discharge is steady for long enough to provide sufficient bedform translation between the successive bathymetric data sets. Bedform velocimetry in small sand- bed rivers is often problematic due to rapid variation within the hydrograph. The bottom-track bias feature of the acoustic Doppler current profiler (ADCP) has been utilized to accurately estimate the virtual velocities of sand-bed rivers. Coupling measurement of the virtual velocity with an accurate determination of the active depth of the streambed sediment movement is another method to measure bedload transport, which will be termed the “virtual velocity” method.
    [Show full text]
  • Geomorphic Classification of Rivers
    9.36 Geomorphic Classification of Rivers JM Buffington, U.S. Forest Service, Boise, ID, USA DR Montgomery, University of Washington, Seattle, WA, USA Published by Elsevier Inc. 9.36.1 Introduction 730 9.36.2 Purpose of Classification 730 9.36.3 Types of Channel Classification 731 9.36.3.1 Stream Order 731 9.36.3.2 Process Domains 732 9.36.3.3 Channel Pattern 732 9.36.3.4 Channel–Floodplain Interactions 735 9.36.3.5 Bed Material and Mobility 737 9.36.3.6 Channel Units 739 9.36.3.7 Hierarchical Classifications 739 9.36.3.8 Statistical Classifications 745 9.36.4 Use and Compatibility of Channel Classifications 745 9.36.5 The Rise and Fall of Classifications: Why Are Some Channel Classifications More Used Than Others? 747 9.36.6 Future Needs and Directions 753 9.36.6.1 Standardization and Sample Size 753 9.36.6.2 Remote Sensing 754 9.36.7 Conclusion 755 Acknowledgements 756 References 756 Appendix 762 9.36.1 Introduction 9.36.2 Purpose of Classification Over the last several decades, environmental legislation and a A basic tenet in geomorphology is that ‘form implies process.’As growing awareness of historical human disturbance to rivers such, numerous geomorphic classifications have been de- worldwide (Schumm, 1977; Collins et al., 2003; Surian and veloped for landscapes (Davis, 1899), hillslopes (Varnes, 1958), Rinaldi, 2003; Nilsson et al., 2005; Chin, 2006; Walter and and rivers (Section 9.36.3). The form–process paradigm is a Merritts, 2008) have fostered unprecedented collaboration potentially powerful tool for conducting quantitative geo- among scientists, land managers, and stakeholders to better morphic investigations.
    [Show full text]
  • Missouri River Floodplain from River Mile (RM) 670 South of Decatur, Nebraska to RM 0 at St
    Hydrogeomorphic Evaluation of Ecosystem Restoration Options For The Missouri River Floodplain From River Mile (RM) 670 South of Decatur, Nebraska to RM 0 at St. Louis, Missouri Prepared For: U. S. Fish and Wildlife Service Region 3 Minneapolis, Minnesota Greenbrier Wetland Services Report 15-02 Mickey E. Heitmeyer Joseph L. Bartletti Josh D. Eash December 2015 HYDROGEOMORPHIC EVALUATION OF ECOSYSTEM RESTORATION OPTIONS FOR THE MISSOURI RIVER FLOODPLAIN FROM RIVER MILE (RM) 670 SOUTH OF DECATUR, NEBRASKA TO RM 0 AT ST. LOUIS, MISSOURI Prepared For: U. S. Fish and Wildlife Service Region 3 Refuges and Wildlife Minneapolis, Minnesota By: Mickey E. Heitmeyer Greenbrier Wetland Services Advance, MO 63730 Joseph L. Bartletti Prairie Engineers of Illinois, P.C. Springfield, IL 62703 And Josh D. Eash U.S. Fish and Wildlife Service, Region 3 Water Resources Branch Bloomington, MN 55437 Greenbrier Wetland Services Report No. 15-02 December 2015 Mickey E. Heitmeyer, PhD Greenbrier Wetland Services Route 2, Box 2735 Advance, MO 63730 www.GreenbrierWetland.com Publication No. 15-02 Suggested citation: Heitmeyer, M. E., J. L. Bartletti, and J. D. Eash. 2015. Hydrogeomorphic evaluation of ecosystem restoration options for the Missouri River Flood- plain from River Mile (RM) 670 south of Decatur, Nebraska to RM 0 at St. Louis, Missouri. Prepared for U. S. Fish and Wildlife Service Region 3, Min- neapolis, MN. Greenbrier Wetland Services Report 15-02, Blue Heron Conservation Design and Print- ing LLC, Bloomfield, MO. Photo credits: USACE; http://statehistoricalsocietyofmissouri.org/; Karen Kyle; USFWS http://digitalmedia.fws.gov/cdm/; Cary Aloia This publication printed on recycled paper by ii Contents EXECUTIVE SUMMARY ....................................................................................
    [Show full text]
  • River Dynamics 101 - Fact Sheet River Management Program Vermont Agency of Natural Resources
    River Dynamics 101 - Fact Sheet River Management Program Vermont Agency of Natural Resources Overview In the discussion of river, or fluvial systems, and the strategies that may be used in the management of fluvial systems, it is important to have a basic understanding of the fundamental principals of how river systems work. This fact sheet will illustrate how sediment moves in the river, and the general response of the fluvial system when changes are imposed on or occur in the watershed, river channel, and the sediment supply. The Working River The complex river network that is an integral component of Vermont’s landscape is created as water flows from higher to lower elevations. There is an inherent supply of potential energy in the river systems created by the change in elevation between the beginning and ending points of the river or within any discrete stream reach. This potential energy is expressed in a variety of ways as the river moves through and shapes the landscape, developing a complex fluvial network, with a variety of channel and valley forms and associated aquatic and riparian habitats. Excess energy is dissipated in many ways: contact with vegetation along the banks, in turbulence at steps and riffles in the river profiles, in erosion at meander bends, in irregularities, or roughness of the channel bed and banks, and in sediment, ice and debris transport (Kondolf, 2002). Sediment Production, Transport, and Storage in the Working River Sediment production is influenced by many factors, including soil type, vegetation type and coverage, land use, climate, and weathering/erosion rates.
    [Show full text]
  • Stream Restoration, a Natural Channel Design
    Stream Restoration Prep8AICI by the North Carolina Stream Restonltlon Institute and North Carolina Sea Grant INC STATE UNIVERSITY I North Carolina State University and North Carolina A&T State University commit themselves to positive action to secure equal opportunity regardless of race, color, creed, national origin, religion, sex, age or disability. In addition, the two Universities welcome all persons without regard to sexual orientation. Contents Introduction to Fluvial Processes 1 Stream Assessment and Survey Procedures 2 Rosgen Stream-Classification Systems/ Channel Assessment and Validation Procedures 3 Bankfull Verification and Gage Station Analyses 4 Priority Options for Restoring Incised Streams 5 Reference Reach Survey 6 Design Procedures 7 Structures 8 Vegetation Stabilization and Riparian-Buffer Re-establishment 9 Erosion and Sediment-Control Plan 10 Flood Studies 11 Restoration Evaluation and Monitoring 12 References and Resources 13 Appendices Preface Streams and rivers serve many purposes, including water supply, The authors would like to thank the following people for reviewing wildlife habitat, energy generation, transportation and recreation. the document: A stream is a dynamic, complex system that includes not only Micky Clemmons the active channel but also the floodplain and the vegetation Rockie English, Ph.D. along its edges. A natural stream system remains stable while Chris Estes transporting a wide range of flows and sediment produced in its Angela Jessup, P.E. watershed, maintaining a state of "dynamic equilibrium." When Joseph Mickey changes to the channel, floodplain, vegetation, flow or sediment David Penrose supply significantly affect this equilibrium, the stream may Todd St. John become unstable and start adjusting toward a new equilibrium state.
    [Show full text]
  • Scour and Fill in Ephemeral Streams
    SCOUR AND FILL IN EPHEMERAL STREAMS by Michael G. Foley , , " W. M. Keck Laboratory of Hydraulics and Water Resources Division of Engineering and Applied Science CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 91125 Report No. KH-R-33 November 1975 SCOUR AND FILL IN EPHEMERAL STREAMS by Michael G. Foley Project Supervisors: Robert P. Sharp Professor of Geology and Vito A. Vanoni Professor of Hydraulics Technical Report to: U. S. Army Research Office, Research Triangle Park, N. C. (under Grant No. DAHC04-74-G-0189) and National Science Foundation (under Grant No. GK3l802) Contribution No. 2695 of the Division of Geological and Planetary Sciences, California Institute of Technology W. M. Keck Laboratory of Hydraulics and Water Resources Division of Engineering and Applied Science California Institute of Technology Pasadena, California 91125 Report No. KH-R-33 November 1975 ACKNOWLEDGMENTS The writer would like to express his deep appreciation to his advisor, Dr. Robert P. Sharp, for suggesting this project and providing patient guidance, encouragement, support, and kind criticism during its execution. Similar appreciation is due Dr. Vito A. Vanoni for his guidance and suggestions, and for generously sharing his great experience with sediment transport problems and laboratory experiments. Drs. Norman H. Brooks and C. Hewitt Dix read the first draft of this report, and their helpful comments are appreciated. Mr. Elton F. Daly was instrumental in the design of the laboratory apparatus and the success of the laboratory experiments. Valuable assistance in the field was given by Mrs. Katherine E. Foley and Mr. Charles D. Wasserburg. Laboratory experiments were conducted with the assistance of Ms.
    [Show full text]
  • Logistic Analysis of Channel Pattern Thresholds: Meandering, Braiding, and Incising
    Geomorphology 38Ž. 2001 281–300 www.elsevier.nlrlocatergeomorph Logistic analysis of channel pattern thresholds: meandering, braiding, and incising Brian P. Bledsoe), Chester C. Watson 1 Department of CiÕil Engineering, Colorado State UniÕersity, Fort Collins, CO 80523, USA Received 22 April 2000; received in revised form 10 October 2000; accepted 8 November 2000 Abstract A large and geographically diverse data set consisting of meandering, braiding, incising, and post-incision equilibrium streams was used in conjunction with logistic regression analysis to develop a probabilistic approach to predicting thresholds of channel pattern and instability. An energy-based index was developed for estimating the risk of channel instability associated with specific stream power relative to sedimentary characteristics. The strong significance of the 74 statistical models examined suggests that logistic regression analysis is an appropriate and effective technique for associating basic hydraulic data with various channel forms. The probabilistic diagrams resulting from these analyses depict a more realistic assessment of the uncertainty associated with previously identified thresholds of channel form and instability and provide a means of gauging channel sensitivity to changes in controlling variables. q 2001 Elsevier Science B.V. All rights reserved. Keywords: Channel stability; Braiding; Incision; Stream power; Logistic regression 1. Introduction loads, loss of riparian habitat because of stream bank erosion, and changes in the predictability and vari- Excess stream power may result in a transition ability of flow and sediment transport characteristics from a meandering channel to a braiding or incising relative to aquatic life cyclesŽ. Waters, 1995 . In channel that is characteristically unstableŽ Schumm, addition, braiding and incising channels frequently 1977; Werritty, 1997.
    [Show full text]
  • Variability of Bed Mobility in Natural Gravel-Bed Channels
    WATER RESOURCES RESEARCH, VOL. 36, NO. 12, PAGES 3743–3755, DECEMBER 2000 Variability of bed mobility in natural, gravel-bed channels and adjustments to sediment load at local and reach scales Thomas E. Lisle,1 Jonathan M. Nelson,2 John Pitlick,3 Mary Ann Madej,4 and Brent L. Barkett3 Abstract. Local variations in boundary shear stress acting on bed-surface particles control patterns of bed load transport and channel evolution during varying stream discharges. At the reach scale a channel adjusts to imposed water and sediment supply through mutual interactions among channel form, local grain size, and local flow dynamics that govern bed mobility. In order to explore these adjustments, we used a numerical flow ␶ model to examine relations between model-predicted local boundary shear stress ( j) and measured surface particle size (D50) at bank-full discharge in six gravel-bed, alternate-bar ␶ channels with widely differing annual sediment yields. Values of j and D50 were poorly correlated such that small areas conveyed large proportions of the total bed load, especially in sediment-poor channels with low mobility. Sediment-rich channels had greater areas of full mobility; sediment-poor channels had greater areas of partial mobility; and both types had significant areas that were essentially immobile. Two reach- mean mobility parameters (Shields stress and Q*) correlated reasonably well with sediment supply. Values which can be practicably obtained from carefully measured mean hydraulic variables and particle size would provide first-order assessments of bed mobility that would broadly distinguish the channels in this study according to their sediment yield and bed mobility.
    [Show full text]
  • Chapter 4: Land Degradation
    Final Government Distribution Chapter 4: IPCC SRCCL 1 Chapter 4: Land Degradation 2 3 Coordinating Lead Authors: Lennart Olsson (Sweden), Humberto Barbosa (Brazil) 4 Lead Authors: Suruchi Bhadwal (India), Annette Cowie (Australia), Kenel Delusca (Haiti), Dulce 5 Flores-Renteria (Mexico), Kathleen Hermans (Germany), Esteban Jobbagy (Argentina), Werner Kurz 6 (Canada), Diqiang Li (China), Denis Jean Sonwa (Cameroon), Lindsay Stringer (United Kingdom) 7 Contributing Authors: Timothy Crews (The United States of America), Martin Dallimer (United 8 Kingdom), Joris Eekhout (The Netherlands), Karlheinz Erb (Italy), Eamon Haughey (Ireland), 9 Richard Houghton (The United States of America), Muhammad Mohsin Iqbal (Pakistan), Francis X. 10 Johnson (The United States of America), Woo-Kyun Lee (The Republic of Korea), John Morton 11 (United Kingdom), Felipe Garcia Oliva (Mexico), Jan Petzold (Germany), Mohammad Rahimi (Iran), 12 Florence Renou-Wilson (Ireland), Anna Tengberg (Sweden), Louis Verchot (Colombia/The United 13 States of America), Katharine Vincent (South Africa) 14 Review Editors: José Manuel Moreno Rodriguez (Spain), Carolina Vera (Argentina) 15 Chapter Scientist: Aliyu Salisu Barau (Nigeria) 16 Date of Draft: 07/08/2019 17 Subject to Copy-editing 4-1 Total pages: 186 Final Government Distribution Chapter 4: IPCC SRCCL 1 2 Table of Contents 3 Chapter 4: Land Degradation ......................................................................................................... 4-1 4 Executive Summary ........................................................................................................................
    [Show full text]
  • Classifying Rivers - Three Stages of River Development
    Classifying Rivers - Three Stages of River Development River Characteristics - Sediment Transport - River Velocity - Terminology The illustrations below represent the 3 general classifications into which rivers are placed according to specific characteristics. These categories are: Youthful, Mature and Old Age. A Rejuvenated River, one with a gradient that is raised by the earth's movement, can be an old age river that returns to a Youthful State, and which repeats the cycle of stages once again. A brief overview of each stage of river development begins after the images. A list of pertinent vocabulary appears at the bottom of this document. You may wish to consult it so that you will be aware of terminology used in the descriptive text that follows. Characteristics found in the 3 Stages of River Development: L. Immoor 2006 Geoteach.com 1 Youthful River: Perhaps the most dynamic of all rivers is a Youthful River. Rafters seeking an exciting ride will surely gravitate towards a young river for their recreational thrills. Characteristically youthful rivers are found at higher elevations, in mountainous areas, where the slope of the land is steeper. Water that flows over such a landscape will flow very fast. Youthful rivers can be a tributary of a larger and older river, hundreds of miles away and, in fact, they may be close to the headwaters (the beginning) of that larger river. Upon observation of a Youthful River, here is what one might see: 1. The river flowing down a steep gradient (slope). 2. The channel is deeper than it is wide and V-shaped due to downcutting rather than lateral (side-to-side) erosion.
    [Show full text]
  • Morphological Bedload Transport in Gravel-Bed Braided Rivers
    Western University Scholarship@Western Electronic Thesis and Dissertation Repository 6-16-2017 12:00 AM Morphological Bedload Transport in Gravel-Bed Braided Rivers Sarah E. K. Peirce The University of Western Ontario Supervisor Dr. Peter Ashmore The University of Western Ontario Graduate Program in Geography A thesis submitted in partial fulfillment of the equirr ements for the degree in Doctor of Philosophy © Sarah E. K. Peirce 2017 Follow this and additional works at: https://ir.lib.uwo.ca/etd Part of the Physical and Environmental Geography Commons Recommended Citation Peirce, Sarah E. K., "Morphological Bedload Transport in Gravel-Bed Braided Rivers" (2017). Electronic Thesis and Dissertation Repository. 4595. https://ir.lib.uwo.ca/etd/4595 This Dissertation/Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact [email protected]. Abstract Gravel-bed braided rivers, defined by their multi-thread planform and dynamic morphology, are commonly found in proglacial mountainous areas. With little cohesive sediment and a lack of stabilizing vegetation, the dynamic morphology of these rivers is the result of bedload transport processes. Yet, our understanding of the fundamental relationships between channel form and bedload processes in these rivers remains incomplete. For example, the area of the bed actively transporting bedload, known as the active width, is strongly linked to bedload transport rates but these relationships have not been investigated systematically in braided rivers. This research builds on previous research to investigate the relationships between morphology, bedload transport rates, and bed-material mobility using physical models of braided rivers over a range of constant channel-forming discharges and event hydrographs.
    [Show full text]
  • Sediment in Alluvial Rivers and Channels
    Module 2 The Science of Surface and Ground Water Version 2 CE IIT, Kharagpur Lesson 10 Sediment Dynamics in Alluvial Rivers and Channels Version 2 CE IIT, Kharagpur Instructional Objectives On completion of this lesson, the student shall be able to learn the following: 1. The mechanics of sediment movement in alluvial rivers 2. Different types of bed forms in alluvial rivers 3. Quantitative assessment of sediment transport 4. Resistance equations for flow 5. Bed level changes in alluvial channels due to natural and artificial causes 6. Mathematical modelling of sediment transport 2.10.0 Introduction In Lesson 2.9, we looked into the aspects of sediment generation due to erosion in the upper catchments of a river and their transport by the river towards the sea. On the way, some of this sediment might get deposited, if the stream power is not sufficient enough. It was noted that it is the shear stress at the riverbed that causes the particles near the bed to move provided the shear is greater than the critical shear stress of the particle which is proportional to the particle size. Hence, the same shear generated by a particular flow may be able to move of say, sand particles, but unable to cause movement of gravels. The particles which move due to the average bed shear stress exceeding the critical shear stress of the particle display different ways of movement depending on the flow condition, sediment size, fluid and sediment densities, and the channel conditions. At relatively slow shear stress, the particles roll or slide along the bed.
    [Show full text]