DOCSLIB.ORG

Advanced Numerical Modeling of Sediment Transport in Gravel-Bed Rivers

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Advanced Numerical Modeling of Sediment Transport in Gravel-Bed Rivers water Article Advanced Numerical Modeling of Sediment Transport in Gravel-Bed Rivers Van Hieu Bui 1,2,* , Minh Duc Bui 1 and Peter Rutschmann 1 1 Institute of Hydraulic and Water Resources Engineering, Technische Universität München, Arcisstrasse 21, D-80333 München, Germany; [email protected] (M.D.B.); [email protected] (P.R.) 2 Faculty of Mechanical Engineering, Thuyloi University, 175 Tay Son, Dong Da, Hanoi 100000, Vietnam * Correspondence: [email protected]; Tel.: +49-152-134-15987 Received: 15 February 2019; Accepted: 13 March 2019; Published: 17 March 2019 Abstract: Understanding the alterations of gravel bed structures, sediment transport, and the effects on aquatic habitat play an essential role in eco-hydraulic and sediment transport management. In recent years, the evaluation of changes of void in bed materials has attracted more concern. However, analyzing the morphological changes and grain size distribution that are associated with the porosity variations in gravel-bed rivers are still challenging. This study develops a new model using a multi-layer’s concept to simulate morphological changes and grain size distribution, taking into account the porosity variabilities in a gravel-bed river based on the mass conservation for each size fraction and the exchange of fine sediments between the surface and subsurface layers. The Discrete Element Method (DEM) is applied to model infiltration processes and to confirm the effects of the relative size of fine sediment to gravel on the infiltration depth. Further, the exchange rate and the bed porosity are estimated while using empirical formulae. The new model was tested on three straight channels. Analyzing the calculated results and comparing with the observed data show that the new model can successfully simulate sediment transport, grain sorting processes, and bed change in gravel-bed rivers. Keywords: numerical modelling; bed porosity; grain sorting; gravel-bed rivers 1. Introduction Sediment transport processes that are due to flowing water in gravel-bed rivers can be formed from bed load, suspended load, and movement inside the bed layer. More importantly, in the same hydraulics condition, the transport rate of coarse size fraction may be different from the rate of fine size fraction. These reasons lead to the distinct forms of gravel-bed rivers. Due to high-flow velocity, all of the finer particles may be eroded, leaving a layer of coarse particles. When the flow is unable to carry the coarse particles, then no more erosion occurs, which is known as an armoring process [1,2]. Inversely, under low-flow conditions, sediment transport can cause the extensive infiltration of fine sediment into void spaces in coarse bed material [3,4], which is also known as clogging or colmation [5,6] (see Figure1). Water 2019, 11, 550; doi:10.3390/w11030550 www.mdpi.com/journal/water Water 2019, 11, 550 2 of 21 Water 2019, 10, x FOR PEER REVIEW 2 of 21 FigureFigure 1. 1. PorosityPorosity variatio variationn of of grain grain system system due due to to fine fine grain grain exchange exchange.. TheThe change change in in grain size distribution ofof coarsecoarse andand finefine sediment sediment not not only only leads leads to to the the variation variation in inbed bed profile, profile but, but it also it also mainly mainly results results in the in changethe change in bed in porosity bed porosity defined defined as a fraction as a fraction of the volume of the volumeof voids of over voids the over total the volume total volume of the gravel-bedof the gravel river.‐bed Accordingriver. According to [7,8 ],to the [7,8 porosity], the porosity of sand-gravel of sand‐ gravelmixtures mixtures can vary can from vary aboutfrom about 0.10 to 0.10 0.50. to For 0.50. example, For example, the measured the measured porosity porosity values values in the in Rhine the RhineRiver River range range from 0.06from to 0.06 0.48 to [9 0.4]. 8 [9]. TheThe study study of variationvariation inin porosity porosity is is vital vital for for fluvial fluvial geomorphology geomorphology assessment assessment as well as well as in as river in riverecosystem ecosystem management. management. From From a river a river management management point point of view, of view, the amount the amount of fine of sediment fine sediment stored storedin the voidin the space void of space gravel-bed of gravel up‐ tobed 22% up [ 10to] may22% be[10 neglected] may be duringneglected calculation during bycalculation considering by consideringconstant porosity. constant Furthermore, porosity. Furthermore the porosity, the may porosity exert may strong exert influence strong oninfluence the rate on of the bed rate level of bedchanges level [changes11,12]. The [11, impact12]. The of impact void space of void of gravel-bedspace of gravel on habitats‐bed on forhabitats fish and for aquaticfish and insects aquatic is insectsessential, is essential, and particularly and particularly the importance the importance of assessing of assessing the change the inchange the void in the structure void structure of the bed of thematerial bed material has been has pointed been pointed out strongly out strongly [13]. [13]. ToTo model model sediment sediment transport transport processes processes as as well well as as bed bed deformation deformation,, multi multi-layer‐layer models models were were appliedapplied for for graded graded sediment sediment transport. transport. Despite Despite the the considerable considerable variations variations of of porosity, porosity, most most of of the the conventionalconventional models models assumed assumed that that the the porosity porosity of of bed material is constant. Therefore, Therefore, sediment sediment transporttransport in in the the form form of infiltration of infiltration into intothe void the spaces void spaces of the co ofarse the bed, coarse or fine bed, particles or fine in particles sublayers in andsublayers the entrainment and the entrainment of fine sediment of fine sedimentinto flow into from flow the from substrates the substrates,, is not taken is not into taken account. into account. This assumptionThis assumption can be can inappropriate be inappropriate for simulating for simulating the sediment the sediment transport transport and bed and variation bed variation in gravel in‐ bedgravel-bed rivers. Toro rivers.‐Escobar Toro-Escobar et al. [14] et al. accounted [14] accounted for this for process this process in terms in terms of an of appropriate an appropriate transfer transfer or exchangeor exchange function function at the at theinterface interface between between the the surface surface layer layer and and substrate. substrate. Based Based on onthe the data data from from a largea large-scale‐scale experiment experiment on onthe the aggradation aggradation and and the theselective selective depositio depositionn of gravel of gravel,, they they proposed proposed an empiricalan empirical form form for the for thetransfer transfer function, function, where where material material that thatis transferred is transferred to the to thesubstrate substrate can canbe representedbe represented as a as weighted a weighted average average of ofbedload bedload and and surface surface material, material, with with a abias bias toward toward bedload. bedload. ApplyingApplying this this function function with with th thee assumption assumption of of a a constant constant porosity, porosity, Cui Cui [ [1515]] developed developed a a numerical numerical modelmodel for for sand sand entrainment/infiltration entrainment/infiltration from/into from/into the the subsurface. subsurface. The The model model was was applied applied to to study study thethe dynamics dynamics of of grain grain size size distributions, distributions, including including the the fractions fractions of sand of sand in sediment in sediment depos depositsits and and on theon channel the channel bed surface. bed surface. Further, Further, Sulaiman Sulaiman et al. [ et16 al.] proposed [16] proposed an approximated an approximated bed variation bed variation model whilemodel considering while considering the change the change in bed inporosity, bed porosity, where where the thickness the thickness of each of eachlayer layer is assumed is assumed to be to constantbe constant and and equal. equal. Furthermore, Furthermore, the the exchange exchange be betweentween bed bed material material and and the the transported transported sediment sediment onlyonly takes takes place place on on the surface layer, andand sedimentsediment transporttransport fromfrom an an upper upper layer layer to to the the lower lower layer layer is isneglected. neglected These. These assumptions assumptions are are improper improper ingravel-bed in gravel‐bed rivers, rivers where, where finer finer sediment sediment possibly possibly drops dropsinto the into subsurface the subsurface layer. layer. To bridge above knowledge gap, in this paper we develop a numerical hydromorphological model that considers the bed porosity change and the exchange flux of fine sediment between two Water 2019, 11, 550 3 of 21 To bridge above knowledge gap, in this paper we develop a numerical hydromorphological model that considers the bed porosity change and the exchange flux of fine sediment between two different bed layers. Further, the Discrete Element Method (DEM) is employed for modeling the infiltration processes. We test the new numerical model for three straight gravel-bed open channels. The calculated results are then compared with the observed data to verify the improved model. 2. Methodology As usual, the structure of our proposed model consists of two modules: (1)—hydrodynamic module; and, (2)—sediment transport and bed variation module. In the hydrodynamic module, the backwater equation is employed for low Froude number conditions and the quasi normal flow assumption is applied for the high Froude number flow conditions. The friction slope is calculated with the Keulegan formulation, which is used for calculating the transport rate in the sediment transport and bed variation module. More details regarding the water flow equations can be found in the studies that were conducted by Cui and Parker [15,17–20].
Load more

Recommended publications
  • (P 117-140) Flood Pulse.Qxp
    117 THE FLOOD PULSE CONCEPT: NEW ASPECTS, APPROACHES AND APPLICATIONS - AN UPDATE Junk W.J. Wantzen K.M. Max-Planck-Institute for Limnology, Working Group Tropical Ecology, P.O. Box 165, 24302 Plön, Germany E-mail: [email protected] ABSTRACT The flood pulse concept (FPC), published in 1989, was based on the scientific experience of the authors and published data worldwide. Since then, knowledge on floodplains has increased considerably, creating a large database for testing the predictions of the concept. The FPC has proved to be an integrative approach for studying highly diverse and complex ecological processes in river-floodplain systems; however, the concept has been modified, extended and restricted by several authors. Major advances have been achieved through detailed studies on the effects of hydrology and hydrochemistry, climate, paleoclimate, biogeography, biodi- versity and landscape ecology and also through wetland restoration and sustainable management of flood- plains in different latitudes and continents. Discussions on floodplain ecology and management are greatly influenced by data obtained on flow pulses and connectivity, the Riverine Productivity Model and the Multiple Use Concept. This paper summarizes the predictions of the FPC, evaluates their value in the light of recent data and new concepts and discusses further developments in floodplain theory. 118 The flood pulse concept: New aspects, INTRODUCTION plain, where production and degradation of organic matter also takes place. Rivers and floodplain wetlands are among the most threatened ecosystems. For example, 77 percent These characteristics are reflected for lakes in of the water discharge of the 139 largest river systems the “Seentypenlehre” (Lake typology), elaborated by in North America and Europe is affected by fragmen- Thienemann and Naumann between 1915 and 1935 tation of the river channels by dams and river regula- (e.g.
    [Show full text]
  • 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]
  • Deposition Patterns and Rates of Mining-Contaminated Sediment Within a Sedimentation Basin System, S.E
    BearWorks Institutional Repository MSU Graduate Theses Spring 2017 Deposition Patterns and Rates of Mining- Contaminated Sediment within a Sedimentation Basin System, S.E. Missouri Joshua Carl Voss Missouri State University - Springfield, [email protected] Follow this and additional works at: http://bearworks.missouristate.edu/theses Part of the Environmental Indicators and Impact Assessment Commons, Environmental Monitoring Commons, and the Hydrology Commons Recommended Citation Voss, Joshua Carl, "Deposition Patterns and Rates of Mining-Contaminated Sediment within a Sedimentation Basin System, S.E. Missouri" (2017). MSU Graduate Theses. 3074. http://bearworks.missouristate.edu/theses/3074 This article or document was made available through BearWorks, the institutional repository of Missouri State University. The orkw contained in it may be protected by copyright and require permission of the copyright holder for reuse or redistribution. For more information, please contact [email protected]. DEPOSITION PATTERNS AND RATES OF MINING-CONTAMINATED SEDIMENT WITHIN A SEDIMENTATION BASIN SYSTEM, BIG RIVER, S.E. MISSOURI A Masters Thesis Presented to The Graduate College of Missouri State University ATE In Partial Fulfillment Of the Requirements for the Degree Master of Science, Geospatial Sciences in Geography, Geology, and Planning By Josh C. Voss May 2017 Copyright 2017 by Joshua Carl Voss ii DEPOSITION PATTERNS AND RATES OF MINING-CONTAMINATED SEDIMENT WITHIN A SEDIMENTATION BASIN SYSTEM, BIG RIVER, S.E. MISSOURI Geography, Geology, and Planning Missouri State University, May 2017 Master of Science Josh C. Voss ABSTRACT Flooding events exert a dominant control over the deposition and formation of floodplains. The rate at which floodplains form depends on flood magnitude, frequency, and duration, and associated sediment transport capacity and supply.
    [Show full text]
  • PRELUDE to SEVEN SLOTS: FILLING and SUBSEQUENT MODIFICATION of SEVEN BROAD CANYONS in the NAVAJO SANDSTONE, SOUTH-CENTRAL UTAH by David B
    PRELUDE TO SEVEN SLOTS: FILLING AND SUBSEQUENT MODIFICATION OF SEVEN BROAD CANYONS IN THE NAVAJO SANDSTONE, SOUTH-CENTRAL UTAH by David B. Loope1, Ronald J. Goble1, and Joel P. L. Johnson2 ABSTRACT Within a four square kilometer portion of Grand Staircase-Escalante National Monument, seven distinct slot canyons cut the Jurassic Navajo Sandstone. Four of the slots developed along separate reaches of a trunk stream (Dry Fork of Coyote Gulch), and three (including canyons locally known as “Peekaboo” and “Spooky”) are at the distal ends of south-flowing tributary drainages. All these slot canyons are examples of epigenetic gorges—bedrock channel reaches shifted laterally from previous reach locations. The previous channels became filled with alluvium, allowing active channels to shift laterally in places and to subsequently re-incise through bedrock elsewhere. New evidence, based on optically stimulated luminescence (OSL) ages, indicates that this thick alluvium started to fill broad, pre-existing, bedrock canyons before 55,000 years ago, and that filling continued until at least 48,000 years ago. Streams start to fill their channels when sediment supply increases relative to stream power. The following conditions favored alluviation in the study area: (1) a cooler, wetter climate increased the rate of mass wasting along the Straight Cliffs (the headwaters of Dry Fork) and the rate of weathering of the broad outcrops of Navajo and Entrada Sandstone; (2) windier conditions increased the amount of eolian sand transport, perhaps destabilizing dunes and moving their stored sediment into stream channels; and (3) southward migration of the jet stream dimin- ished the frequency and severity of convective storms.
    [Show full text]
  • Urban Flooding Mitigation Techniques: a Systematic Review and Future Studies
    water Review Urban Flooding Mitigation Techniques: A Systematic Review and Future Studies Yinghong Qin 1,2 1 College of Civil Engineering and Architecture, Guilin University of Technology, Guilin 541004, China; [email protected]; Tel.: +86-0771-323-2464 2 College of Civil Engineering and Architecture, Guangxi University, 100 University Road, Nanning 530004, China Received: 20 November 2020; Accepted: 14 December 2020; Published: 20 December 2020 Abstract: Urbanization has replaced natural permeable surfaces with roofs, roads, and other sealed surfaces, which convert rainfall into runoff that finally is carried away by the local sewage system. High intensity rainfall can cause flooding when the city sewer system fails to carry the amounts of runoff offsite. Although projects, such as low-impact development and water-sensitive urban design, have been proposed to retain, detain, infiltrate, harvest, evaporate, transpire, or re-use rainwater on-site, urban flooding is still a serious, unresolved problem. This review sequentially discusses runoff reduction facilities installed above the ground, at the ground surface, and underground. Mainstream techniques include green roofs, non-vegetated roofs, permeable pavements, water-retaining pavements, infiltration trenches, trees, rainwater harvest, rain garden, vegetated filter strip, swale, and soakaways. While these techniques function differently, they share a common characteristic; that is, they can effectively reduce runoff for small rainfalls but lead to overflow in the case of heavy rainfalls. In addition, most of these techniques require sizable land areas for construction. The end of this review highlights the necessity of developing novel, discharge-controllable facilities that can attenuate the peak flow of urban runoff by extending the duration of the runoff discharge.
    [Show full text]
  • Lesson 4: Sediment Deposition and River Structures
    LESSON 4: SEDIMENT DEPOSITION AND RIVER STRUCTURES ESSENTIAL QUESTION: What combination of factors both natural and manmade is necessary for healthy river restoration and how does this enhance the sustainability of natural and human communities? GUIDING QUESTION: As rivers age and slow they deposit sediment and form sediment structures, how are sediments and sediment structures important to the river ecosystem? OVERVIEW: The focus of this lesson is the deposition and erosional effects of slow-moving water in low gradient areas. These “mature rivers” with decreasing gradient result in the settling and deposition of sediments and the formation sediment structures. The river’s fast-flowing zone, the thalweg, causes erosion of the river banks forming cliffs called cut-banks. On slower inside turns, sediment is deposited as point-bars. Where the gradient is particularly level, the river will branch into many separate channels that weave in and out, leaving gravel bar islands. Where two meanders meet, the river will straighten, leaving oxbow lakes in the former meander bends. TIME: One class period MATERIALS: . Lesson 4- Sediment Deposition and River Structures.pptx . Lesson 4a- Sediment Deposition and River Structures.pdf . StreamTable.pptx . StreamTable.pdf . Mass Wasting and Flash Floods.pptx . Mass Wasting and Flash Floods.pdf . Stream Table . Sand . Reflection Journal Pages (printable handout) . Vocabulary Notes (printable handout) PROCEDURE: 1. Review Essential Question and introduce Guiding Question. 2. Hand out first Reflection Journal page and have students take a minute to consider and respond to the questions then discuss responses and questions generated. 3. Handout and go over the Vocabulary Notes. Students will define the vocabulary words as they watch the PowerPoint Lesson.
    [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]
  • Sandbridge Beach FONSI
    FINDING OF NO SIGNIFICANT IMPACT Issuance of a Negotiated Agreement for Use of Outer Continental Shelf Sand from Sandbridge Shoal in the Sandbridge Beach Erosion Control and Hurricane Protection Project Virginia Beach, Virginia Pursuant to the National Environmental Policy Act (NEPA), Council on Environmental Quality regulations implementing NEPA (40 CFR 1500-1508) and Department of the Interior (DOI) regulations implementing NEPA (43 CFR 46), the Bureau of Ocean Energy Management (BOEM) prepared an environmental assessment (EA) to determine whether the issuance of a negotiated agreement for the use of Outer Continental Shelf (OCS) sand from Sandbridge Shoal Borrow Areas A and B for the Sandbridge Beach Erosion Control and Hurricane Protection Project near Virginia Beach, VA would have a significant effect on the human environment and whether an environmental impact statement (EIS) should be prepared. Several NEPA documents evaluating impacts of the project have been previously prepared by both the US Army Corps of Engineers (USACE) and BOEM. The USACE described the affected environment, evaluated potential environmental impacts (initial construction and nourishment events), and considered alternatives to the proposed action in a 2009 EA. This EA was subsequently updated and adopted by BOEM in 2012 in association with the most recent 2013 Sandbridge nourishment effort (BOEM 2012). Prior to this, BOEM (previously Minerals Management Service [MMS]) was a cooperating agency on several EAs for previous projects (MMS 1997; MMS 2001; MMS 2006). This current EA, prepared by BOEM, supplements and summarizes the aforementioned 2012 analysis. BOEM has reviewed all prior analyses, supplemented additional information as needed, and determined that the potential impacts of the current proposed action have been adequately addressed.
    [Show full text]
  • Sediment Transport and the Genesis Flood — Case Studies Including the Hawkesbury Sandstone, Sydney
    Sediment Transport and the Genesis Flood — Case Studies including the Hawkesbury Sandstone, Sydney DAVID ALLEN ABSTRACT The rates at which parts of the geological record have formed can be roughly determined using physical sedimentology independently from other dating methods if current understanding of the processes involved in sedimentology are accurate. Bedform and particle size observations are used here, along with sediment transport equations, to determine rates of transport and deposition in various geological sections. Calculations based on properties of some very extensive rock units suggest that those units have been deposited at rates faster than any observed today and orders of magnitude faster than suggested by radioisotopic dating. Settling velocity equations wrongly suggest that rapid fine particle deposition is impossible, since many experiments and observations (for example, Mt St Helens, mud- flows) demonstrate that the conditions which cause faster rates of deposition than those calculated here are not fully understood. For coarser particles the only parameters that, when varied through reasonable ranges, very significantly affect transport rates are flow velocity and grain diameter. Popular geological models that attempt to harmonize the Genesis Flood with stratigraphy require that, during the Flood, most deposition believed to have occurred during the Palaeozoic and Mesozoic eras would have actually been the result of about one year of geological activity. Flow regimes required for the Flood to have deposited various geological cross- sections have been proposed, but the most reliable estimate of water velocity required by the Flood was attained for a section through the Tasman Fold Belt of Eastern Australia and equalled very approximately 30 ms-1 (100 km h-1).
    [Show full text]
  • Sediment Transport in the San Francisco Bay Coastal System: an Overview
    Marine Geology 345 (2013) 3–17 Contents lists available at ScienceDirect Marine Geology journal homepage: www.elsevier.com/locate/margeo Sediment transport in the San Francisco Bay Coastal System: An overview Patrick L. Barnard a,⁎, David H. Schoellhamer b,c, Bruce E. Jaffe a, Lester J. McKee d a U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA, USA b U.S. Geological Survey, California Water Science Center, Sacramento, CA, USA c University of California, Davis, USA d San Francisco Estuary Institute, Richmond, CA, USA article info abstract Article history: The papers in this special issue feature state-of-the-art approaches to understanding the physical processes Received 29 March 2012 related to sediment transport and geomorphology of complex coastal–estuarine systems. Here we focus on Received in revised form 9 April 2013 the San Francisco Bay Coastal System, extending from the lower San Joaquin–Sacramento Delta, through the Accepted 13 April 2013 Bay, and along the adjacent outer Pacific Coast. San Francisco Bay is an urbanized estuary that is impacted by Available online 20 April 2013 numerous anthropogenic activities common to many large estuaries, including a mining legacy, channel dredging, aggregate mining, reservoirs, freshwater diversion, watershed modifications, urban run-off, ship traffic, exotic Keywords: sediment transport species introductions, land reclamation, and wetland restoration. The Golden Gate strait is the sole inlet 9 3 estuaries connecting the Bay to the Pacific Ocean, and serves as the conduit for a tidal flow of ~8 × 10 m /day, in addition circulation to the transport of mud, sand, biogenic material, nutrients, and pollutants.
    [Show full text]
  • Secondary Flow Effects on Deposition of Cohesive Sediment in A
    water Article Secondary Flow Effects on Deposition of Cohesive Sediment in a Meandering Reach of Yangtze River Cuicui Qin 1,* , Xuejun Shao 1 and Yi Xiao 2 1 State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China 2 National Inland Waterway Regulation Engineering Research Center, Chongqing Jiaotong University, Chongqing 400074, China * Correspondence: [email protected]; Tel.: +86-188-1137-0675 Received: 27 May 2019; Accepted: 9 July 2019; Published: 12 July 2019 Abstract: Few researches focus on secondary flow effects on bed deformation caused by cohesive sediment deposition in meandering channels of field mega scale. A 2D depth-averaged model is improved by incorporating three submodels to consider different effects of secondary flow and a module for cohesive sediment transport. These models are applied to a meandering reach of Yangtze River to investigate secondary flow effects on cohesive sediment deposition, and a preferable submodel is selected based on the flow simulation results. Sediment simulation results indicate that the improved model predictions are in better agreement with the measurements in planar distribution of deposition, as the increased sediment deposits caused by secondary current on the convex bank have been well predicted. Secondary flow effects on the predicted amount of deposition become more obvious during the period when the sediment load is low and velocity redistribution induced by the bed topography is evident. Such effects vary with the settling velocity and critical shear stress for deposition of cohesive sediment. The bed topography effects can be reflected by the secondary flow submodels and play an important role in velocity and sediment deposition predictions.
    [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]