DOCSLIB.ORG

The Pool-Riffle Sequence As the Principal Design Component Of

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

THE POOL-RIFFLE SEQUENCE AS THE PRINCIPAL DESIGN COMPONENT OF LOW-GRADIENT, MEANDERING, GMWL-BED CHANNELS A Thesis Presented to The Facdty of Graduate Studies of The University of Guelph by A.M. HARTLEY In partial filfilment of requirements for the degree of Master of Science Apnl, 1999 O A. Mark Hartley, 1999 National Library Bibliothèque nationale I*m of Canada du Canada Acquisitions and Acquisitions et Bibliographic Services services bibliographiques 395 Wellington Street 395. me Wellington OttawaON KIA ON4 Ottawa ON K1A ON4 Canada Canada Yow hk Votre referenca Our tüe Notre reldrence The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant a La National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sel1 reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfichelfilm, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fkom it Ni la thèse ni des extraits substantiels may be printed or othenvise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. ABSTRACT THE POOL-RLFFLE SEQUENCE AS THE PRINCIPAL DESIGN COMPONENT OF LOW-GRADIENT, MEANDERING GRAVEL-BED CHANNELS A. Mark Hartley, P.Eng. Advisor: University of Guelph, 1999 Dr. Hugh Whiteiey Channel design methods have recently been eqanded in Southem Ontario to consider the form and fuaction of channek observed in nature. These efforts have recognized sipifkant geomorphic (sinuosity, entrenchment, bedforms) and fish habitat features of a river. Recent case studies and design guidance documents recognize the three dimensional structure of rivers but the hydraulic properties are pooriy characterïzed. Bedforms provide a usefùr focal point for the characterization of geometric, fluvial as well as hydradic characteristics. Bedforms have a dominant effect on the variables used in the standard-step backwater equation during flows equal to or less than banl6ull stage. Measurements of these variables at the upstream and downstrearn ends of bedforms, in this case pools and riffles, were collected at one reach of the Credit River and one reach of Whitemans Creek. Results indicated that geomeûic (bed elevation) and fluvial (water depth, shear veIocity) characteristics were signifïcantly difEerent between nfEles and pools within a reach, between riBies of the two reaches and between pools of the two reaches. Hydraulic characteristics (grain and form energy losses) were not significantiy Werent due to high variabiliv and low sarnple number. The energy-Ioss coefficient may be as high a 2.0 and is rareIy Iess that 1.5. A design procedure far pool-rime sequences in low-gradient gravel-bed channels is presented as weii as recommendations for Mer work. This research has been a classical exercise in education by discovery and has been greatly enhancecl by several considerable contributions, both financial and scholastic. I would like to thank my Advisory Cornmittee, Drs. Whiteley, Dickinson and Kostaschuk for giving me the freedom to "explore the possibikties" yet not aUowing any significant deviations from what seemed to me to be a rnoving target. This thesis would not have been completed doutJudy7s gentle reminders and Peggy's endless patience, my reiiable "contacts" with the University; 1997 was a tough year - thanks for your help Thanks to Bill A~ablefor "showing me the ropes", teaching me the "Rosgen method" through the many, rnany long days spent in the field and evenings spent c'discussing the days workx and helping me to stay away fiom the "classical" channel design methodologies by stresshg ''let the rivsr teach us". The high qualis custorn-designed equipment bdt by the School of Engineering technical stafT, Paul and Bill, was critical to the collection of good field data; 1 couldn7thave done it without them. 1 would to thank Bill Snodgrass for dowing me the use of the velocity meter for such a long period of tirne. It's amazing what you can do with good equipment. Financial support was provided by the National Science and Engineering Research Council, the Grand River Conservation Authority and the American Fisheries Society - Southem Ontario Chapter. 1 greatly appreciate the assistance provided by the Grand River Conservation AuthorXty and the Credit Vdey Conservation for aiiowiag me access to the reaches within their watersheds. Last but not 1- words cannot begh to describe the shear volurne of unquestioning support, understanding and fkith provided by my de, Doina. When the water appeared the darkest and deepest, your soothing words, radiant srnile and gentle hand pulied me through. Dedicated to my parents, Norman Aiderson Hartley 1933 - 1997 Elizabeth Ann Hartiey 1933 - 1997 TABLE OF CONTENTS 1.0 INTRODUCTION ................. ....... ........... ...t ................................................................................. 1 2.0 BACKGROUND.......................................................................................................................... 5 2.1 DESIGMNGR~~TERC~ANNELS ............................... .... ..................................................................... 6 2.1.1 Recently Date loped Procedures................................................................................................... 6 2.1.2 Recent Channel Consh-uctiodRestorationEfforts ...................................................................... 12 2.2 R~VERCHANNELS AND CLASSIFICATIONSYSTEMS ............................................................................... 13 2.3 LARGESCALE CHARACTERISTICS OF RIVERS....................................................................................... 19 2.3.1 Physiography and River VaDeys ............................................................................................... 19 2.3.2 Meandering ofriver channeCs .................................................................................................... 21 2.3.3 Dominant Discharge .................................................................................................................. 23 2-4 MORPHOLOGYOF GRAVEL-BEDRTVERS ............................................................................................ 25 2.4.1 Bedforms in grave[-bed rivers - Rifles and Pools ...................................................................... 25 2.4.2 Physical Characteristics ofRzfles and Pools ............................................................................. 27 2.4.2.1 Longitudinal Dimensions................................................................................................................... 27 2.4.2.2 Cross Sectional Features ..................................................................................................................... 28 2.4.2.3 Bed Roughness.................................................................................................................................... 30 2.4.3 Fluvial Characteristics ofRifles and Pools .............................................................................. 32 2.4.3.1 Flow resistance ................................................................................................................................ 32 2.4.3.2 Energy Losses ..................................................................................................................................... 36 2.4.4 Env ironmentaf Sign~pcanceof Riffles and Pools: Fish Habitat .............................................. 39 3.0 STUDY OBJECTIVES................................................................................................................... 43 4.0 METHODOLOGY....................................................................................................................... 45 4.1 SmSELECTION ................................................................................................................................ 45 4.2 FIELDWORK ..................................................................................................................................... 48 3.2 1 Topographie Survey. .................................................................................................................. 51 4.2.2 Water SmceElmations ........................................................................................................... 52 ............................................................ 4.2.3 Veloci~Profiles ............................................................ 52 3.2.4 Substrate Particle Size ............................................................................................................... 53 4.3 DATAANALYSIS................................................................................................................................ 53 4.3.1 Flow Durution and Flood Frequency ......................................................................................... 53 43.2 Geomorphic Characteristics of Rifles & Pools .......................................................................... 53 43.3 Velocj~Distribution and Energy Losses .................................................................................... 54 5.0 RESULTS AND DISCUSSION ....................................................................................................
Recommended publications
  • Measurement of Bedload Transport in Sand-Bed Rivers: a Look at Two Indirect Sampling Methods

    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.
  • Geomorphic Classification of Rivers

    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.
  • Seasonal Flooding Affects Habitat and Landscape Dynamics of a Gravel

    Seasonal Flooding Affects Habitat and Landscape Dynamics of a Gravel

    Seasonal flooding affects habitat and landscape dynamics of a gravel-bed river floodplain Katelyn P. Driscoll1,2,5 and F. Richard Hauer1,3,4,6 1Systems Ecology Graduate Program, University of Montana, Missoula, Montana 59812 USA 2Rocky Mountain Research Station, Albuquerque, New Mexico 87102 USA 3Flathead Lake Biological Station, University of Montana, Polson, Montana 59806 USA 4Montana Institute on Ecosystems, University of Montana, Missoula, Montana 59812 USA Abstract: Floodplains are comprised of aquatic and terrestrial habitats that are reshaped frequently by hydrologic processes that operate at multiple spatial and temporal scales. It is well established that hydrologic and geomorphic dynamics are the primary drivers of habitat change in river floodplains over extended time periods. However, the effect of fluctuating discharge on floodplain habitat structure during seasonal flooding is less well understood. We collected ultra-high resolution digital multispectral imagery of a gravel-bed river floodplain in western Montana on 6 dates during a typical seasonal flood pulse and used it to quantify changes in habitat abundance and diversity as- sociated with annual flooding. We observed significant changes in areal abundance of many habitat types, such as riffles, runs, shallow shorelines, and overbank flow. However, the relative abundance of some habitats, such as back- waters, springbrooks, pools, and ponds, changed very little. We also examined habitat transition patterns through- out the flood pulse. Few habitat transitions occurred in the main channel, which was dominated by riffle and run habitat. In contrast, in the near-channel, scoured habitats of the floodplain were dominated by cobble bars at low flows but transitioned to isolated flood channels at moderate discharge.
  • Culvert Design Transportation & the Environment Conference December 3, 2014 Chris Freiburger – Fisheries Division - DNR Perched Piping

    Culvert Design Transportation & the Environment Conference December 3, 2014 Chris Freiburger – Fisheries Division - DNR Perched Piping

    Culvert Design Transportation & the Environment Conference December 3, 2014 Chris Freiburger – Fisheries Division - DNR Perched Piping Blockage Sediment What are we after? •Natural and dynamic stream channel •Passage of all aquatic organisms •Low maintenance, flood-resilient road Sizing & Placement of Stream Culverts The Stream Will Tell You! •Match Culvert Width to Bankfull Stream Width •Extend Culvert Length through side slope toe •Set Culvert Slope same as Stream Slope •Bury Culvert 1/6th Bankfull Stream Width •Offset Multiple Culverts (floodplain ~ splits lower buried one) (higher one ~ 1 ft. higher) •Align Culvert with Stream (or dig with stream sinuosity) •Consider Headcuts and Cut-Offs Dr. Sandy Verry Chief Research Hydrologist Forest Service Mesboac Culvert Design – 0’ • Match 3’ Bankfull width 6’ • Extend Culvert to side slope toe • Set on Channel Slope Set Slope Failure to set culverts on the same slope th as the stream (and bury them 1/6 widthBKF) is the single reason that many culverts do not allow for fish passage! Slope can be measured as: Slope along the bank (wider variation, than thalweg) Slope of the water surface (big errors at low flow or in flooded channels, good at moderate to bankfull flows) Slope of the thalweg (this, by far, is the best one) Measure a longitudinal profile to allow the precise placement of culverts. Precision Setting is the key to a fully functional riffle culvert installation At each point riffle 1. Bankfull riffle 2. Water surface Setting the elevation 3. Thalweg of the culvert invert True North Backsight upstream & riffle Benchmark downstream assures success! riffle riffle Measure Bankfull elevation, water surface elevation, and major thalweg topographic breaks (riffle top, riffle bottom, pool bottom), at each station, on the longitudinal profile 1997 LITTLE POKEGAMA CREEK PLOT 7 LONGITUDINAL 1003 1002 1001 1000 FT - 999 998 Bankfull elevation 997 ELEVATION 996 Slope = 0.0191 Water Surface elevation 995 Thalweg elevation 994 993 0 50 100 150 200 250 300 350 400 THALWEG DISTANCE-FT 1.
  • Missouri River Floodplain from River Mile (RM) 670 South of Decatur, Nebraska to RM 0 at St

    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 ....................................................................................
  • Stream Restoration, a Natural Channel Design

    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.
  • Logistic Analysis of Channel Pattern Thresholds: Meandering, Braiding, and Incising

    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.
  • Sediment in Alluvial Rivers and Channels

    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.
  • Total Bed-Material Discharge in Alluvial Channels

    Total Bed-Material Discharge in Alluvial Channels

    Total Bed-Material Discharge in Alluvial Channels GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1498-1 Total Bed-Material Discharge in Alluvial Channels By F. M. CHANG, D. B. SIMONS, and E. V. RICHARDSON STUDIES OF FLOW IN ALLUVIAL CHANNELS GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1498-1 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1965 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C., 20402 - Price 20 cents (paper cover) CONTENTS Page Symbols_ _______________________________________________________ iv Abstract__ _____________________________________________________ I 1 Introduction._ ____________________________________________________ 1 Scope._______________________________________________________ 1 Acknowledgments. ____________________________________________ 3 Analysis of sediment size.__________________________________________ 3 Velocity distribution in alluvial channels____________________________ 5 Bed-material discharge._------__-______-_-_________________________ 8 Contact-bed-material discharge________________________________ 10 Suspended-bed-material discharge.______________________________ 13 Total bed-material discharge._________-_____-_-___________----__ 16 Evaluation.__________________________________________________ 18 Summary and conclusions__--_-__________-_-__-___-_______--_-___ 20 References_ _ ____________________________________________________ 22 ILLUSTRATIONS Page FIGURE 1. Bed-material size distribution of sands for flume data____ 12 2. Relation of sediment Reynolds number and von Karman's coefficient. ______________________________ _ ______ 7 3-6. Comparison of theoretical and measured velocity dis­ tribution for flume data 3. For de=0.19-mm sand ___ ___________________ 7 4. For de=0.33-, 0.35-mm sand. _________------_- 8 5. For de=0.50-, 0.52-mm sand___._._ _ ___._.__ 9 6. For rfe=0.93-mm sand ____ __._ ______ _-__ 9 7.
  • 5.1 Coarse Bed Load Sampling

    5.1 Coarse Bed Load Sampling

    University of Montana ScholarWorks at University of Montana Graduate Student Theses, Dissertations, & Professional Papers Graduate School 1997 The initiation of coarse bed load transport in gravel bed streams Andrew C. Whitaker The University of Montana Follow this and additional works at: https://scholarworks.umt.edu/etd Let us know how access to this document benefits ou.y Recommended Citation Whitaker, Andrew C., "The initiation of coarse bed load transport in gravel bed streams" (1997). Graduate Student Theses, Dissertations, & Professional Papers. 10498. https://scholarworks.umt.edu/etd/10498 This Dissertation is brought to you for free and open access by the Graduate School at ScholarWorks at University of Montana. It has been accepted for inclusion in Graduate Student Theses, Dissertations, & Professional Papers by an authorized administrator of ScholarWorks at University of Montana. For more information, please contact [email protected]. INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter free, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps.
  • Objective Identification of Pools and Riffles in a Human-Modified Stream System

    Objective Identification of Pools and Riffles in a Human-Modified Stream System

    Middle States Geographer, 2002, 35:52-60 OBJECTIVE IDENTIFICATION OF POOLS AND RIFFLES IN A HUMAN-MODIFIED STREAM SYSTEM Kelly M. Frothingham and Natalie Brown Department of Geography & Planning, Buffalo State College 1300 Elmwood Avenue Buffalo, NY 14222 ABSTRACT: Pools have been defined as topographic lows along a longitudinal stream profile and riffles are topographic highs. Past research has shown pools and riffles are the fundamental bedforms in meandering streams and that channel cross sections in meandering channels exhibit varying degrees of asymmetry that coincide with these bed form features. Two indices that identify pool and riffle bed forms are the bed differencing technique (bdt) developed by O'Neill and Abrahams (1984) and the areal difference asymmetry index (A') (Knighton. 1981). The purpose of this research was to use these indices to objectively identify pools and riffles in three reaches of a human-modified stream. Geomorphological data were collected in two meandering reaches and one straight reach ofthe East Branch ofCazenovia Creek, NY. Between 16 and 19 cross sections were surveyed in each reach during summer low flow conditions. The bdt identified more bed forms in the meandering reaches versus the straight channelized reach (six and two bed forms, respectively). Results from the asymmetry' analysis indicated that more cross sections in the two meandering reaches were asymmetrical (71 and 73% ofthe cross sections) versus 47% of the cross sections being asymmetrical in the straight reach. Moreover, asymmetrical cross sections generally corresponded with pool bed forms identified by the bdt and symmetrical cross sections corresponded with riffle bed forms identified hy the bdt.
  • Re-Creating Meander Geometry Photo(S)

    Re-Creating Meander Geometry Photo(S)

    Practice Title Re-creating meander geometry Photo(s) Greene County streams after their meander geometry was restored to the extent necessary to move sediment and flow without excess erosion or deposition (bottom photos). The proper meander geometry is determined through detailed stream assessment. Also, a diagram showing the typical position of pools and riffles within a meandering stream, and a few other stream meander geometry patterns (top). Summary of Practice The winding pattern of a river or stream is called its meander pattern. These meanders result in a longer channel with a lower slope. These curves slow down the water and absorb energy, which helps to reduce the potential for erosion. The velocity of a stream is typically greatest on the outside of a meander bend. The increased force of this water often results in erosion along this bank, extending a short distance downstream. On the inside of the bend, the stream velocity typically decreases, which often results in the deposition of sediment, usually sand and gravel. If you could look at the long-term history of a valley over hundreds or thousands of years, you would see that the stream has moved back and forth across the valley bottom. In fact, this lateral migration of the channel, accompanied by down cutting, is what has formed the valley. Success in stream management is based on working with the stream, not against it. If a reach of channel is suffering unusual bank erosion, down cutting of the bed, aggradation, change of channel pattern, or other evidence of instability, a realistic approach to addressing these problems should be based on restoring the system’s equilibrium.