See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/247332796 Rapid Evaluation of Sediment Budgets Book · January 1996 CITATIONS READS 211 250 2 authors: Leslie Margaret Reid Thomas Dunne US Forest Service University of California, Sa… 44 PUBLICATIONS 1,668 178 PUBLICATIONS 13,713 CITATIONS CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: Modeling of hillslope evolution by water erosion View project All content following this page was uploaded by Thomas Dunne on 17 September 2015. The user has requested enhancement of the downloaded file. Leslie M. Reid & Thomas Dunne RAPID EVALUATION OF SEDIMENT BUDGETS GeoEcology paperback Die Deutsche Bibliothek - CIP Einheitsaufnahme Reid, Leslie M.: Rapid evaluation of sediment budgets / Leslie M. Reid & Thomas Dunne. - Reiskirchen : Catena Verl., 1996 (GeoEcology paperback) ISBN 3-923881-39-5 NE: Dunne, Thomas: © Copyright 1996 by CATENA VERLAG GMBH, 35447 Reiskirchen, Germany All rights are reserved. No part of this publication may be reproduced. stored in a retrieval system or transmitted in any form or by any means, electronic. mechanical, photocopying. recording or otherwise, without prior permission of the publisher. This publication has been registered with the Copyright Clearance Center, Inc. Submission of an article for publication implies the transfer of the copyright from the author(s) to the publisher. ISBN 3-923381-39-5 Table of Contents List of Figures List of Tables List of Boxes List of Symbols Abstract Acknowledgements 1 INTRODUCTION 1 1.1 Definition and description 3 1.2 Relation to other methods 5 1.3 Misconceptions 6 1.4 How to use this volume 7 2 PROCEDURE FOR SEDIMENT BUDGET CONSTRUCTION 9 Step 1. Define the problem 9 Step 2. Acquire background information 10 Step 3. Subdivide area 13 Step 4. Interpret aerial photographs 14 Step 5. Conduct fieldwork 16 Step 6. Analyze data 19 Step 7. Check results 20 3 EVALUATING SEDIMENT PRODUCTION FROM HILLSLOPES AND CHANNELS 20 3.1 Overview of shillslope sediment production 22 3.2 Identification of sediment sources 25 3.3 Rates of discrete erosion processes 27 3.3.1 Landslides 27 3.3.2 Debris flows 30 3.3.3 Gullies 31 3.3.4 Treethrow 34 3.3.5 Animal burrows 35 3.4 Rates of chronic erosion processes 36 3.4.1 Sheetwash erosion 36 3.4.2 Wind erosion 41 3.4.3 Dry ravel 43 3.4.4 Bank erosion 43 3.5 Other hillslope sediment transport processes 44 3.6 Sediment delivery from hillslopes to channels 47 3.7 Grain-size composition 50 3.8 Calculation of long-term rates 52 3.9 Predicting future erosion rates 59 4 EVALUATING SEDIMENT TRANSPORT AND STORAGE IN CHANNELS 60 4.1 Overview of channel processes 62 4.2 Characterization of channels 63 4.2.1 Qualitative characterization 63 4.2.2 Selection of measurement sites 65 4.2.3 Slope measurements 67 4.2.4 Channel geometry measurements 68 4.2.5 Channel roughness 69 4.2.6 Definition of flow characteristics 70 4.2.7 Identification of channel changes 71 4.3 Grain-size distributions 73 4.4 Initiation of bed-material transport 83 4.5 Determination of scour depths 90 4.6 Sediment transport rates in channels 92 4.6.1 Sediment transport equations 93 4.6.2 Comparison of transport predictions and measurements 94 4.6.3 Applying sediment transport equations 106 4.6.4 Use of field observations 113 4.6.5 Evaluation of the washload component 114 4.6.6 Limits of sediment transport predictions 116 4.7 Sediment storage 116 4.7.1 Identifying storage elements in channels 117 4.7.2 Defining trends in channel-related sediment storage 118 4.8 Computations of sediment yield 123 5 EXAMPLES OF SEDIMENT BUDGET APPLICATIONS 124 5.1 West slope of the Sierra Nevada, Californai 127 5.2 Shinyanga Region, Tanzania 130 5.3 Snoqualmie River basin, Washington 132 5.4 Olympic Peninsula rivers, Washington 133 6 CONCLUSIONS 135 APPENDIX 1. GLOSSARY 138 APPENDIX 2. ADDITIONAL READING AND USEFUL COMPENDIA 144 Background information 144 Manuals and descriptions of particular methods 146 Data compendia 147 REFERENCES 149 List of Figures 1. Simple flowchart of sediment transport on hillslopes and in channels 4 2. Definition of subareas based on bedrock and vegetation type 13 3. Sequential aerial photographs 15 4. Examples of increasingly complex flowcharts 17 5. Flowchart that indicates typical relation between sediment mobilization, production, deposition, and yield 20 6. Examples of external growth nodes 28 7. Graph of cumulative landslide volume as a function of age of the landslide 29 8. Flowchart indicating the relation of sediment transported by debris flows to sediment produced from hillslopes 31 9. Relation between gully cross-sectional area and gully width 32 10. Use of root exposure and erosion mounds to estimate surface erosion rates 37 II. Correlation between erosion-intensity class and measured recent rates of erosion in Kenya 41 12. Grain-size distribution of average annual sediment yields from 6 small catchments 52 13. Calculation of long-term landsliding rate 54 14. The error function (erf) of Urn 55 15. Landslide frequency versus road age 58 16. Components of the sediment load in a channel 62 17. Example of the relation between low-flow and high-flow water-surface profiles 69 18. Grain-size distribution of colluvium in hollows and alluvium from channels in a 4th-order basin 74 19. Grain-size distributions of channel sediment at River Mile 22 of the Snoqualmie river, Washington 75 20. Contour map of bed elevations in a meander 81 21. Percent of a channel-bed pavement that is intermittently mobile at various shear stresses 87 22. Comparisons of shear stress for initial motion of particles of various sizes predicted using initial-motion equations and those measured by Milhouse 88 23. Phases in the erosion of landslide deposits or other sediment stored behind dams of organic debris 120 24. Flow chart illustrating relationships between various processes of colluvium transport into small streams studied in the N. Fork Kings River basin 128 25. Variation along the Humptulis River of average annual rates of bedload transport 135 List of Tables 1. Recent examples of rapidly constructed sediment budgets 2 2. Common problems addressed by hillslope-based sediment budgets 21 3. Common sources of sediment affected by various land uses 26 4. Ordinal-scale classification scheme for sheetwash erosion severity 40 5. Erosion measurements on roads and paths 42 6. Examples of questions concerning channels that can be addressed by sediment budgeting 61 7. Equations for initiation of motions 85 8. Sediment transport equations A. Bedload 94 B. Total bed-material load or suspended bed-material load 95 9. Tests of sediment transport equations in natural channels A. Gravel-bedded channels 96 B. Sand-bedded channels 97 10. Histograms of modal values for sediment load equations 99 II. Potentially useful sediment transport equations for channels of various types 100 12. Characteristics of streams used to test sediment transport formulas A. Gravel-bedded channels 102 B. Sand-bedded channels 103 13. Studies that compare transport equations with data from natural channels 104 14. Expected proportions of bedload in total load 114 15. Sediment budgeting studies 125 16. Results of selected sediment budget studies 126 17. Comparisons of measured sediment yields with those calculated using sediment budgets 137 List of Boxes 1. Typical resource assessment problem 1 2. Sediment budget definition 3 3. Is a new method applicable to your problem? 8 4. Steps in sediment budget construction 9 5. Acquiring aerial photographs and maps 12 6. Evidence for activity of erosion and sediment transport processes 23 7. Indicators of surface erosion 24 8. Sample calculation of soil creep input 46 9. Recognizing sediment deposits 48 10. Calculating total sediment from a grain size trapped 49 11. Why you can't describe the world from your desk 51 12. Calculation of long-term landslide frequencies 56 13. Selecting a useful channel reach for analysis 66 14. Recognizing bankfull stage 68 15. Considerations in the use of historical evidence 72 16. Evidence of channel bed stability 75 17. A rapid field method for sieving gravel 76 18. Determining the required sample size for a pebble count 79 19. Example of a calculation of required sample size for 0 50 80 20. How comparisons are noted in Table 9 98 21. Defining the zone of active transport 107 22. Checklist for applying sediment transport equations 110 23. Evidence for channel aggradation 121 List of Symbols a constant a' factor in Hey's velocity equation A channel cross-sectional area Ab cross-sectional area of bankfull channel Aw area of catchment Awf area of catchment: future Awp area of catchment: past Agf agriculture factor in bank erosion equation b constant C constant dmax maximum depth of scour or fill in channel df cross-sectional average of fill depth in channel ds cross-sectional average of scour depth in channel D particle diameter Di particle diameter of interest Dg geometric mean of particle diameters D, diameter of tree D50sub median particle diameter in subsurface D IO median particle diameter D84 particle diameter than which 84% of the grains are smaller DD drainage density erf error function E(y) expected value ofy, given probability density of fiY) f Darcy-Weisbach friction factor fly) probability density of y g acceleration due to gravity (approximately 980 cm/s2) h flow depth he flow depth at which particle begins to move h.n height of root mound h.nax maximum flow depth H, hydraulic