Sediment Transport Flow and Morphological Processes Edited by Faruk Bhuiyan SEDIMENT TRANSPORT – FLOW PROCESSES AND MORPHOLOGY Edited by Faruk Bhuiyan INTECHOPEN.COM Sediment Transport - Flow and Morphological Processes http://dx.doi.org/10.5772/1827 Edited by Faruk Bhuiyan Contributors P K Bhunya, Ronny Berndtsson, Raj Dev Singh, C S P Ojha, Ram Balachandar, Prashanth Reddy Hanmaiahgari, Faruk Bhuiyan, Dong Chen, Ronald Bingner, Henrique Momm, Robert Wells, Seth Dabney, Mervyn Peart, Fok Lincoln, Chen Ji, J.T. Andrews, Muhammet Emin Emiroglu, José Fortes Lopes, Takahiro Shiono, Kuniaki Miyamoto, Alireza Keshavarzi, James Ball, Chien-Chih Chen, Jia-Jyun Dong, Chih-Yu Kuo, Ruey-Der Hwang, Ming-Hsu Li, Chyi-Tyi Lee © The Editor(s) and the Author(s) 2011 The moral rights of the and the author(s) have been asserted. All rights to the book as a whole are reserved by INTECH. 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Notice Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher. No responsibility is accepted for the accuracy of information contained in the published chapters. The publisher assumes no responsibility for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained in the book. First published in Croatia, 2011 by INTECH d.o.o. eBook (PDF) Published by IN TECH d.o.o. Place and year of publication of eBook (PDF): Rijeka, 2019. IntechOpen is the global imprint of IN TECH d.o.o. Printed in Croatia Legal deposit, Croatia: National and University Library in Zagreb Additional hard and PDF copies can be obtained from orders@intechopen.com Sediment Transport - Flow and Morphological Processes Edited by Faruk Bhuiyan p. cm. ISBN 978-953-307-374-3 eBook (PDF) ISBN 978-953-51-4911-8 Selection of our books indexed in the Book Citation Index in Web of Science™ Core Collection (BKCI) Interested in publishing with us? Contact book.department@intechopen.com Numbers displayed above are based on latest data collected. For more information visit www.intechopen.com 4,100+ Open access books available 151 Countries delivered to 12.2% Contributors from top 500 universities Our authors are among the Top 1% most cited scientists 116,000+ International authors and editors 120M+ Downloads We are IntechOpen, the world’s leading publisher of Open Access books Built by scientists, for scientists Meet the editor Dr. Faruk Bhuiyan is a water resources specialist with a civil engineering background. He has more than 15 years of experience in teaching, research and consul- tancy related to sediment transport and river processes. As a commonwealth scholar he obtained Ph.D from the School of Environmental Sciences, University of East Anglia, UK. Dr. Bhuiyan’s interests encompass field studies, laboratory experimentation and numerical modeling in several areas including large alluvial river processes (e.g., the Ganges and Brah- maputra-Jamuna Rivers), variably saturated groundwater flow modeling and river basin management issues. He visited and worked in a number of institutions including Hydraulic Research Wallingford Ltd. (UK), Delft University of Technology (The Netherlands), Loughborough University (UK) and University of Windsor (Canada). As a Visiting Professor in the Department of Civil and Environmental Engineering, University of Al- berta, he conducted researches on fish micro-habitat, entrainment during hydropower operation, CFD modeling and sediment mound formation. Contents Preface XI Chapter 1 A Sediment Graph Model Based on SCS-CN Method 1 P. K. Bhunya, Ronny Berndtsson, Raj Deva Singh and S.N.Panda Chapter 2 Bed Forms and Flow Mechanisms Associated with Dunes 35 Ram Balachandar and H. Prashanth Reddy Chapter 3 Stochastic Nature of Flow Turbulence and Sediment Particle Entrainment Over the Ripples at the Bed of Open Channel Using Image Processing Technique 69 Alireza Keshavarzi and James Ball Chapter 4 Stochastic and Deterministic Methods of Computing Graded Bedload Transport 93 Faruk Bhuiyan Chapter 5 Methods for Gully Characterization in Agricultural Croplands Using Ground-Based Light Detection and Ranging 101 Henrique Momm, Ronald Bingner, Robert Wells and Seth Dabney Chapter 6 Modeling Channel Response to Instream Gravel Mining 125 Dong Chen Chapter 7 Modeling of Sediment Transport in Surface Flow with a Grass Strip 141 Takahiro Shiono and Kuniaki Miyamoto Chapter 8 Clear-Water Scour at Labyrinth Side Weir Intersection Along the Bend 157 M. Emin Emiroglu Chapter 9 On the Influence of the Nearbed Sediments in the Oxygen Budget of a Lagunar System: The Ria de Aveiro - Portugal 177 José Fortes Lopes X Contents Chapter 10 Environmental Observations on the Kam Tin River, Hong Kong 207 Mervyn R. Peart, Lincoln Fok and Ji Chen Chapter 11 Unraveling Sediment Transport Along Glaciated Margins (the Northwestern Nordic Seas) Using Quantitative X-Ray Diffraction of Bulk (< 2mm) Sediment 225 J.T. Andrews Chapter 12 Reconstruction of the Kinematics of Landslide and Debris Flow Through Numerical Modeling Supported by Multidisciplinary Data: The 2009 Siaolin, Taiwan Landslide 249 Chien-chih Chen, Jia-Jyun Dong, Chih-Yu Kuo, Ruey-Der Hwang, Ming-Hsu Li and Chyi-Tyi Lee Preface It is my pleasure to write the preface of the book “Sediment Transport - Flow and Morphological Processes ” published by Intech Open Access Publisher. The transport of sediment in the turbulent flow comprises of complex phenomena. Although sediment transport due to water flow is directly related with long-term and short-term alteration of the earth's surface, which has significance in science, engineering and environmental applications, up until now the scientific progress in quantifying the relevant processes has been rather slow. This explains the reason for abundance of empiricism and independent field observations in this discipline. It has been several decades since the advent of our understanding on micro-level turbulence properties of fluid flows that we have started to apply our knowledge on turbulence for transport in geophysical boundary layers. Intech Open Access Publisher has taken a good step to publish a series of books on the issues of sediment transport. The participation to the current book is by special invitation to authors selected based on their previous contributions in recognized scientific journals. Consequently, contents of the chapters are the reflections of the authors’ research thoughts. This book provides indications on current knowledge, research and applications of sediment transport processes. The first three chapters of the book present basic and advanced knowledge on flow mechanisms and transport. These are followed by examples of modeling efforts and individual case studies on erosion-deposition and their environmental consequences. I believe that the materials of this book would help a wide range of readers to update their insight on fluvial transport processes. Finally, I would like to thank Intech Open Access Publisher for inviting me to contribute as a book editor. Special thanks are also due to the Publishing Process Manager for her cooperation and help during preparation of the book. Dr Faruk Bhuiyan Department of Water Resources Engineering Bangladesh University of Engineering & Technology (BUET), Dhaka, Bangladesh 1 A Sediment Graph Model Based on SCS-CN Method P. K. Bhunya 1 , Ronny Berndtsson 2 , Raj Deva Singh 1 and S.N. Panda 3 1National Institute of Hydrology, Roorkee, Uttarakhand 2Dept. of Water Resources Engineering, Lund University, Lund, 3 Indian Institute of Technology, Kharagpur WB 1,3 India 2 Sweden 1. Introduction Sediment is fragmented material primarily formed by the physical and chemical disintegration of rocks from the earth's crust. For example, physical disintegration means where the material is broken down by human interference or can be due to the construction or engineering works. Similarly chemical disintegration is by chemicals in fluids, wind, water or ice and/or by the force of gravity acting on the particle itself. The estimation of sediment yield is needed for studies of reservoir sedimentation, river morphology and soil and water conservation planning. However, sediment yield estimate of a watershed is difficult as it results due to a complex interaction between topographical, geological and soil characteristics. In spite of extensive studies on the erosion process and sediment transport modelling, there exists a lack of universally accepted sediment yield formulae (Bhunya et al. 2010). The conditions that will transport sediment are needed for engineering problems, for example, during canal construction, channel maintenance etc. Interpreting ancient sediments; most sediments are laid down under processes associated with flowing water like rivers, ocean currents and tides. Usually, the transport of particles by rolling, sliding and saltating is called bed-load transport, while the suspended particles are transported as suspended load transport. The suspended load may also include the fine silt particles brought into suspension from the catchment area rather than from, the streambed material (bed material load) and is called the wash load. An important characteristic of wash load is that its concentration is approximately uniform for all points of the cross-section of a river. This implies that only a single point measurement is sufficient to determine the cross-section integrated wash-load transport by multiplying with discharge. In estuaries clay and silt concentrations are generally not uniformly distributed. Bed load refers to the sediment which is in almost continuous contact with the bed, carried forward by rolling, sliding or hopping. Suspended load refers to that part of the total sediment transport which is maintained in suspension by turbulence in the flowing water for considerable periods of time without contact with the stream bed. It moves with practically Sediment Transport – Flow Processes and Morphology 2 the same velocity as that of the flowing water. That part of the suspended load which is composed of particle sizes smaller than those found in appreciable quantities in the bed material. It is in near-permanent suspension and therefore, is transported through the stream without deposition. The discharge of the wash load through a reach depends only on the rate with which these particles become available in the catchment area and not on the transport capacity of the flow. Fluid flow and sediment transport are obviously linked to the formation of primary sedimentary structures. Here in this chapter, we tackle the question of how sediment moves in response to flowing water that flows in one direction. 2. Fluid flow and sediment transport The action of sediment transport which is maintained in the flowing water is typically due to a combination of the force of gravity acting on the sediment and/or the movement of the fluid. A schematic diagram of these forces in a flowing water is shown in Figure 1. The bottom plate is fixed and the top plate is accelerated by applying some force that acts from left to right. The upper plate will be accelerated to some terminal velocity and the fluid between the plate will be set into motion. Terminal velocity is achieved when the applied force is balanced by a resisting force (shown as an equal but opposite force applied by the stationary bottom plate). Fig. 1. Varying forces acting on flowing water along the flow depth The shear stress transfers momentum (mass times velocity) through the fluid to maintain the linear velocity profile. The magnitude of the shear stress is equal to the force that is applied to the top plate. The relationship between the shear stress, the fluid viscosity and the velocity gradient is given by: du dy (1a) A Sediment Graph Model Based on SCS-CN Method 3 Where u is the velocity, y is the fluid depth at this point as given in figure, is the fluid viscosity, and is the shear stress. From this relationship we can determine the velocity at any point within the column of fluid. Rearranging the terms: / du dy or ( / ) dy du or ( / ) y u y c (1b) where c (the constant of integration) is the velocity at y=0 (where u=0) such that: y u y From this relationship we can see the following: a. That the velocity varies in a linear fashion from 0 at the bottom plate (y=0) to some maximum at the highest position (i.e., at the top plate). b. That as the applied force (equal to ) increases so does the velocity at every point above the lower plate. c. That as the viscosity increases the velocity at any point above the lower plate decreases. Driving force is only the force applied to the upper, moving plate, and the shear stress (force per unit area) within the fluid is equal to the force that is applied to the upper plate. Fluid momentum is transferred through the fluid due to viscosity. 3. Fluid gravity flows Water flowing down a slope in response to gravity e.g. in rivers, the driving force is the down slope component of gravity acting on the mass of fluid; more complicated because the deeper into the flow the greater the weight of overlying fluid. In reference to Figure 2 that shows the variation in velocity along the flowing water, D is the flow depth and y is some height above the boundary, FG is the force of gravity acting on a block of fluid with dimensions, (D-y) x 1 x 1; here y is the height above the lower boundary, is the slope of the water surface, it may be noted here that the depth is uniform so that this is also the slope of the lower boundary, and y is the shear stress that is acting across the bottom of the block of fluid and it is the down slope component of the weight of fluid in the block at some height y above the boundary. Fig. 2. Variation in velocity for depth Sediment Transport – Flow Processes and Morphology 4 For this general situation, y , the shear stress acting on the bottom of such a block of fluid that is some distance y above the bed can be expressed as follows: ( ) 1 1 sin( ) y g D y (2) The first term in the above equation i.e. ( ) 1 1 g D y is the weight of water in the block and Sin ( ) is the proportion of that weight that is acting down the slope. Clearly, the deeper within the water i.e. with decreasing y the greater the shear stress acting across any plane within the flow. At the boundary y = 0, the shear stress is greatest and is referred to as the boundary shear stress ( o ); this is the force per unit area acting on the bed which is available to move sediment. Setting y =0: 0 ( )sin( ) g D y and y du d y (3a) From the above equations, we get the following velocity distribution for such flows by substituting / ( )sin( ) / du dy g D y (3b) Integrating with respect to y : 2 ( ) ( / 2) y gSin gSin du u d y D y d y c y D y c dy (4) Where c is the constant of integration and equal to the velocity at the boundary (Uy=0) such that: 2 sin 2 y g y u yD (5) Fig. 3. Variation in velocity for depth Velocity varies as an exponential function from 0 at the boundary to some maximum at the water surface; this relationship applies to: A Sediment Graph Model Based on SCS-CN Method 5 a. Steady flows: not varying in velocity or depth over time. b. Uniform flows: not varying in velocity or depth along the channel. c. Laminar flows: see next section. 3.1 The classification of fluid gravity flows 3.1.1 Flow Reynolds’ Number (R) Reynolds’s experiments involved injecting a dye streak into fluid moving at constant velocity through a transparent tube. Fluid type, tube diameter and the velocity of the flow through the tube were varied, and the three types of flows that were classified are as follows: (a) Laminar Flo w: every fluid molecule followed a straight path that was parallel to the boundaries of the tube, (b) Transitional Flow : every fluid molecule followed wavy but parallel path that was not parallel to the boundaries of the tube, and (c) Turbulent Flow : every fluid molecule followed very complex path that led to a mixing of the dye. Reynolds’s combined these variables into a dimensionless combination now known as the Flow Reynolds’ Number ( R ) where: UD R (6a) Where U is the velocity of the flow, is the density of the fluid , D is the diameter of the tube, and is the fluid’s dynamic viscosity. Flow Reynolds’ number is often expressed in terms of the fluid’s kinematic viscosity ( ) equally expressed as units are m 2 /s) and UD R (6b) The value of R determine the type of flows in the following manner: a. Laminar flows : R <1000 b. Transitional flows : 1000 < R <2000 c. Turbulent flows : R >2000 Fig. 4. Reynolds’s experiments for different types of flows Sediment Transport – Flow Processes and Morphology 6 In laminar flows, the fluid momentum is transferred only by viscous shear; a moving layer of fluid drags the underlying fluid along due to viscosity (see the left diagram, below). The velocity distribution in turbulent flows has a strong velocity gradient near the boundary and more uniform velocity (an average) well above the boundary. The more uniform distribution well above the boundary reflects the fact that fluid momentum is being transferred not only by viscous shear. The chaotic mixing that takes place also transfers momentum through the flow. The movement of fluid up and down in the flow, due to turbulence, more evenly distributes the velocity, low speed fluid moves upward from the boundary and high speed fluid in the outer layer moves upward and downward. This leads to a redistribution of fluid momentum. Fig. 5. Variation in velocity for depth at three different types of flows Turbulent flows are made up of two regions. And there is an inner region near the boundary that is dominated by viscous shear i.e., y du dy (7) And, an outer region that is dominated by turbulent shear which focus on transfer of fluid momentum by the movement of the fluid up and down in the flow. y du du dy dy (8) Where is the eddy viscosity which reflects the efficiency by which turbulence transfers momentum through the flow. A Sediment Graph Model Based on SCS-CN Method 7 Fig. 6. Two regions of turbulent shear As a result, the formula for determining the velocity distribution of a laminar flow cannot be used to determine the distribution for a turbulent flow as it neglects the transfer of momentum by turbulence. Experimentally, determined formulae are used to determine the velocity distribution in turbulent flows e.g. the Law of the Wall for rough boundaries under turbulent flows: * 2.3 8.5 log y o u y U y ; y 0 (= d/30), * 0/ U and 0 ( ) gDSin (9) Where is Von Karman’s constant which is generally taken 0.41 for clear water flows lacking sediment, y is the height above the boundary, y 0 (= d/30) and d is grain size, and U* is the shear velocity of the flow. If the flow depth and shear velocity are known, as well as the bed roughness, this formula can be used to determine the velocity at any height y above the boundary. * 0 2.3 8.5 log y y u U y (10a) * 2.3 8.5 lo g ( ) y u U gDSin (10b) The above formula may be used to estimate the average velocity of a turbulent flow by setting y to 0.4 times the depth of the flow i.e. y = 0.4D. Experiments have shown that the average velocity is at 40% of the depth of the flow above the boundary. Sediment Transport – Flow Processes and Morphology 8 3.1.2 Flow Froude Number (F) Classification of flows according to their water surface behaviour, is an important part of the basis for classification of flow regime a. F < 1 has a sub critical flow (tranquil flow) b. F = 1 has a critical flow c. F > 1 has a supercritical flow (shooting flow) Flow Froude Number (F) is defined as follow: gD U F (11) gD = the celerity (speed of propagation) of gravity waves on a water surface. F < 1, U < gD : water surface waves will propagate upstream because they move faster than the current. Bed forms are not in phase with the water surface. F > 1, U > gD : water surface waves will be swept downstream because the current is moving faster than they can propagate upstream. Bed forms are in phase with the water surface. In sedimentology the Froude number, is important to predict the type of bed form that will develop on a bed of mobile sediment. Fig. 7. Classification of flows according to degree of Froude Number