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Water-Worked Bedload: Hydrodynamic and Mass Transport

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A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Hydraulics and Hydrodynamics".

Deadline for manuscript submissions: closed (29 March 2019) | Viewed by 36257

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Prof. Dr. Paweł M. Rowiński

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Guest Editor

Institute of Geophysics, Polish Academy of Sciences, ul. Księcia Janusza 64, 01-452 Warsaw, Poland
Interests: mathematical modelling of hydrological processes; fluvial hydraulics; river turbulence; pollution; heat and sediment transport in rivers

Prof. Subhasish Dey

E-Mail Website
Guest Editor

Indian Institute of Technology Kharagpur, Department of Civil Engineering, Kharagpur 721302, West Bengal, India
Interests: applied hydrodynamics; turbulence; fluvial hydraulics; shallow fluid flows

Special Issue Information

Dear Colleagues,

Flow over a streambed that is complex in nature, especially in the near-bed flow zone, has been a topic of continued research interest over several decades due to its practical importance. It is even more complicated due to flow unsteadiness that intensifies transport processes and causes morphological changes in rivers. Our knowledge on how sediment is transported under unsteady flow conditions is still insufficient, which triggers a good deal of experimental, theoretical and computational efforts. The near-bed flow is greatly influenced by a complex, colossal fluid-sediment interaction which gives rise to a spatial flow heterogeneity in addition to an enhanced temporal intermittency in the near-bed flow zone. In a natural river, the flow velocity plays a major role in developing the bed surface topography formed by the roughness elements. To be specific, the sediment particles at the bed surface are in motion if the flow velocity is greater than the threshold velocity of sediment particle motion. Thus, the surface topography of a natural bed exhibits a spatially multifaceted three-dimensional organization, because it is created by the transport processes as a result of the continual deposition and reworking due to fluvial processes. In this way, a so-called water-worked bed is formed in a natural river. On the other hand, in laboratory experimental studies, a simulated streambed is generally prepared depositing randomly mixed sediments to a given thickness into the experimental flume. The streambed surface is then scraped and levelled, forming a screeded bed. Nevertheless, in the laboratory, if the distribution of scaled sediment size is at par with the natural bed sediment size (prototype), the simulated streambed can be deemed acceptable provided that the bed surface characteristics in laboratory flume are analogous to those in the prototype. To be specific, the screeded bed is essentially a mixture of randomly sorted sediments and its statistical distributions in terms of bed surface topography are unable to appropriately represent a water-worked bed, even though the bed surface formed by the sediment has a same particle size distribution. Importantly, the signature of the bed roughness characteristics is essentially transmitted to the characteristics of the time-averaged flow, turbulence parameters and resistance to flow.

Prof. Paweł M. Rowiński
Prof. Subhasish Dey
Guest Editors

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Keywords

bedload
bed shear stress
bed surface topography
fluvial hydraulics
streambed hydrodynamics
sediment transport
turbulence
water-worked bed

Published Papers (10 papers)

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Editorial

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3 pages, 167 KiB

Open AccessEditorial

Water-Worked Bedload: Hydrodynamics and Mass Transport

by Paweł M. Rowiński and Subhasish Dey

Water 2019, 11(7), 1396; https://doi.org/10.3390/w11071396 - 07 Jul 2019

Viewed by 1633

Abstract

Turbulent flow over a natural streambed is complex in nature, especially in the near-bed flow zone, because a natural water-worked bed exhibits a spatially complex, three-dimensional structure [...] Full article

(This article belongs to the Special Issue Water-Worked Bedload: Hydrodynamic and Mass Transport)

Research

Jump to: Editorial, Review

11 pages, 4196 KiB

Open AccessArticle

Roughness Effect of Submerged Groyne Fields with Varying Length, Groyne Distance, and Groyne Types

by Ronald Möws and Katinka Koll

Water 2019, 11(6), 1253; https://doi.org/10.3390/w11061253 - 14 Jun 2019

Cited by 13 | Viewed by 2840

Abstract

Design guidelines were developed for a number of in-stream structures; however, the knowledge about their morphological and hydraulic function is still incomplete. A variant is submerged groynes, which aim to be applicable for bank protection especially in areas with restricted flood water levels due to their shallow height. Laboratory experiments were conducted to investigate the backwater effect and the flow resistance of submerged groyne fields with varying and constant field length and groyne distance. The effect of the shape of a groyne model was investigated using two types of groynes. The validity of different flow types, from “isolated roughness” to “quasi smooth”, was analyzed in relation to the roughness density of the groyne fields. The results show a higher backwater effect for simplified groynes made of multiplex plates, compared to groynes made of gravel. The relative increase of the upstream water level was lower at high initial water levels, for short length of the groyne field, and for larger distance between the single groynes. The highest roughness of the groyne fields was found at roughness densities, which indicated wake interference flow. Considering a mobile bed, the flow resistance was reduced significantly. Full article

(This article belongs to the Special Issue Water-Worked Bedload: Hydrodynamic and Mass Transport)

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15 pages, 7145 KiB

Open AccessFeature PaperArticle

The Logarithmic Law of the Wall in Flows over Mobile Lattice-Arranged Granular Beds

by Federica Antico, Ana M. Ricardo and Rui M. L. Ferreira

Water 2019, 11(6), 1166; https://doi.org/10.3390/w11061166 - 04 Jun 2019

Cited by 4 | Viewed by 3123

Abstract

The purpose of the present paper is to provide further insights on the definition of the parameters of the log-law in open-channel flows with rough mobile granular beds. Emphasis is placed in the study of flows over cohesionless granular beds composed of monosized spherical particles in simple lattice arrangements. Potentially influencing factors such as grain size distribution, grain shape and density or cohesion are not addressed in this study. This allows for a preliminary discussion of the amount of complexity needed to obtain the log-law features observed in more realistic open-channel flows. Data collection included instantaneous streamwise and bed-normal flow velocities, acquired with a two-dimensional and two-component (2D2C) Particle Image Velocimetry (PIV) system. The issue of the non uniqueness of the definition of the parameters of the log-law is addressed by testing several hypotheses. In what concerns the von Kármán parameter,

κ

, it is considered as flow-independent or flow-dependent (a fitting parameter). As for the geometric roughness scale,

k_{s}

, it results from a best fit procedure or is computed from a roughness function. In the latter case, the parameter B is imposed as

8.5

or is calculated from the best fit estimate. The analysis of the results reveals that a flow dependent von Kármán parameter, lower than the constant

κ

0.40

, should be preferred. Forcing

κ

0.40

leads to non-physical values of

k_{s}

and would imply extending the inner layer up about 50% of the flow depth which is physically difficult to explain. Considering a flow dependent von Kármán parameter allows for coherent explanations for the values of the remaining parameters (the geometric roughness scale

k_{s}

, the displacement height

Δ

, the roughness height

z_{0}

). In particular, for the same transport rate, the roughness height obtained in a natural sediment bed is much greater than in the case of bed made of monosized glass spheres, underlining the influence of the bed surface complexity (texture and self-organized bed forms, in the water-worked cases) on the definition of the log-law parameters. Full article

(This article belongs to the Special Issue Water-Worked Bedload: Hydrodynamic and Mass Transport)

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15 pages, 5032 KiB

Open AccessFeature PaperArticle

Bed-Load Transport in Two Different-Sized Mountain Catchments: Mlynne and Lososina Streams, Polish Carpathians

by Artur Radecki-Pawlik, Piotr Kuboń, Bartosz Radecki-Pawlik and Karol Plesiński

Water 2019, 11(2), 272; https://doi.org/10.3390/w11020272 - 04 Feb 2019

Cited by 9 | Viewed by 3697

Abstract

The prediction and calculation of the volume of gravel and/or sand transported down streams and rivers—called bed-load transport is one of the most difficult things for river engineers and designers because, in addition to field measurements, personnel involved in such activities need to be highly experienced. Bed-load transport treated by many engineers marginally or omitted and often receives only minor consideration from engineers or may be entirely disregarded simply because they do not know how to address the issue—in many cases, this is a fundamental problem in river management tasks such as: flood protection works; river bank protection works against erosion; building bridges and culverts; building water reservoirs and dams; checking dams and any other hydraulic structures. Thus, to share our experience in our paper, bed-load transport was calculated in two river/stream mountain catchments, which are different in terms of the characteristics of the catchment area and the level of river engineering works performed along the stream channel—both are tributaries of the Dunajec River and have similar Carpathian flysh geology. The studies were performed in the Mlyne stream and in the Lososina River in Polish Carpathians. Mlynne is one of the streams in the Gorce Mountains—it is prone to flash flooding events and has caused many problems with floods in the past. It flows partially in the natural river channel and partially in a trained river channel lined with concrete revetments. The stream bed load is accumulated in the reservoir upstream of the check dam. The Lososina River is one of the Polish Carpathian mountainous streams which crosses the south of the Beskid Wyspowy Mountains. It mostly has a gravel bed and it is flashy and experiences frequent flooding spring. At the mouth of the Lososina River, there is one of the largest Polish Carpathian artificial lakes—the Czchow lake. The Lososina mostly transports gravel as the bed load to the Czchow water reservoir where the sediment is deposited. In the early seventies, the Lososina was partly canalised, especially in places where passes inhabited areas. The paper compares the situation of bed-load transport in the Lososina River before and after engineering training works showing how much sediment is transported downstream along the river channel to the Czchow artificial lake. Also compared is the Mlynne bed load transport upstream and downstream from the check dam showing how much sediment might be transported and deposited in the reservoir upstream from the check dam and when one could expect this reservoir to be clogged. Full article

(This article belongs to the Special Issue Water-Worked Bedload: Hydrodynamic and Mass Transport)

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17 pages, 4156 KiB

Open AccessFeature PaperArticle

Distribution and Potential Risk of Heavy Metals in Sediments of the Three Gorges Reservoir: The Relationship to Environmental Variables

by Lei Huang, Hongwei Fang, Ke Ni, Wenjun Yang, Weihua Zhao, Guojian He, Yong Han and Xiaocui Li

Water 2018, 10(12), 1840; https://doi.org/10.3390/w10121840 - 12 Dec 2018

Cited by 11 | Viewed by 3014

Abstract

In this study, surface sediment samples were taken from the Three Gorges Reservoir (TGR) in June 2015 to estimate the spatial distribution and potential risk of Cu, Zn, Cd, Pb, Cr, and Ni (34 sites from the mainstream and 9 sites from the major tributaries), and correlations with environmental variables were analyzed (e.g., median sediment size, water depth, turbidity, dissolved oxygen of the bottom water samples, and total organic carbon, total nitrogen, and total phosphorus of the surface sediment samples). Results show that the heavy metal concentrations in the sediments have increased over the last few decades, especially for Cd and Pb; and the sites in the downstream area, e.g., Badong (BD) and Wushan (WS), have had greater increments of heavy metal concentrations. The sampling sites from S6 to S12-WS are identified as hot spots for heavy metal distribution and have relatively high heavy metal concentrations, and there are also high values for the sites affected by urban cities (e.g., the concentrations of Zn, Cd, Cr and Ni for the site S12-WS). Overall, the heavy metal concentrations increased slightly along the mainstream due to pollutants discharged along the Yangtze River and sediment sorting in the reservoir, and the values in the mainstream were greater than those in the tributaries. Meanwhile, the heavy metal concentrations were generally positively correlated with water depth (especially for Ni), while negatively correlated with dissolved oxygen, turbidity, and median sediment size. These environmental variables have a great impact on the partition of heavy metals between the sediment and overlying water. According to the risk assessment, the heavy metals in the surface sediments of TGR give a low to moderate level of pollution. Full article

(This article belongs to the Special Issue Water-Worked Bedload: Hydrodynamic and Mass Transport)

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15 pages, 7802 KiB

Open AccessArticle

The 3-D Morphology Evolution of Spur Dike Scour under Clear-Water Scour Conditions

by Li Zhang, Hao Wang, Xianqi Zhang, Bo Wang and Jian Chen

Water 2018, 10(11), 1583; https://doi.org/10.3390/w10111583 - 05 Nov 2018

Cited by 12 | Viewed by 3698

Abstract

By changing the alignment angle of spur dike, this study focused on the evolution of scour hole morphology in three alignments under clear-water scour conditions, including the 3-D structure of the scour hole, 2-D profile morphological evolution process and the evolution characteristics of the local bed shear stress. The results show that the plane area and volume of the scour hole both are power functions over time, which is similar to the evolution characteristics of scour depth. Local scour includes three stages: The initial stage, development stage and balance stage. The local bed shear stress presents successively: τ_b > τ_c, τ_b = τ_c and τ_b < τ_c. Based on this characteristic, the evolution mechanism between scour hole morphology and the local bed shear stress is further clarified. Furthermore, although the alignment of the spur dike significantly affects the longitudinal and vertical dimension erosion rates of the scour hole, the scour hole morphology is not only relatively constant but also has a specific proportion, and the evolution process is orderly in the whole process of evolution. To the scouring equilibrium state, the length of the scour hole on the upstream and downstream of the spur dike is approximately in line with the golden section feature. The related results provide technical support for scour parameter design and scour hole protection of spur dike in flood period. Full article

(This article belongs to the Special Issue Water-Worked Bedload: Hydrodynamic and Mass Transport)

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18 pages, 5541 KiB

Open AccessArticle

Experimental Investigations of Interactions between Sand Wave Movements, Flow Structure, and Individual Aquatic Plants in Natural Rivers: A Case Study of Potamogeton Pectinatus L.

by Łukasz Przyborowski, Anna Maria Łoboda and Robert Józef Bialik

Water 2018, 10(9), 1166; https://doi.org/10.3390/w10091166 - 30 Aug 2018

Cited by 10 | Viewed by 3660

Abstract

Long-duration measurements were performed in two sandy bed rivers, and three-dimensional (3D) flow velocity and bottom elevation changes were measured in a vegetated area and in a clear region of a river. Detailed flow velocity profiles downstream and upstream of a single specimen of Potamogeton pectinatus L. were obtained and the bed morphology was assessed. Potamogeton plants gathered from each river were subjected to tensile and bending tests. The results show that the existence of the plants was influenced by both bottom and flow conditions, as the plants were located where water velocity was lower by 12% to 16% in comparison to clear region. The characteristics of the flow and sand forms depended on the cross-sectional arrangement of the river, e.g., dunes were approximately four times higher in the middle of the river than in vegetated regions near the bank. Furthermore, the studied hydrophytes were too sparse to affect water flow and had no discernible impact on the sand forms’ movements. The turbulent kinetic energy downstream of a single plant was reduced by approximately 25%. Additionally, the plants’ biomechanical characteristics and morphology were found to have adjusted to match the river conditions. Full article

(This article belongs to the Special Issue Water-Worked Bedload: Hydrodynamic and Mass Transport)

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13 pages, 5000 KiB

Open AccessArticle

Geometric Characteristics of Spur Dike Scour under Clear-Water Scour Conditions

by Li Zhang, Pengtao Wang, Wenhai Yang, Weiguang Zuo, Xinhong Gu and Xiaoxiao Yang

Water 2018, 10(6), 680; https://doi.org/10.3390/w10060680 - 24 May 2018

Cited by 16 | Viewed by 4786

Abstract

Factors such as flow and sediment characteristics affecting the spur dike’s local depth of erosion have yielded considerable research results, but there is little discussion of the geometry of the spur dike’s local scour holes. This study focuses on the spatial characteristics of the geometry of local scour holes in straight-wall spur dikes. The discussion shows that the spur dike arrangement clearly changes the plane geometry of the scour hole. The maximum scour depth has a power function relationship with the area of the scour hole and the scour hole-volume. Moreover, the ratio of the product of the maximum scour depth and the plane area of the scour hole to the scour hole-volume is a fixed constant. The average slope of upstream of the scour hole and along the axis direction of the spur dike is slightly larger than the angle of repose of the sediment, the slope distribution of the scour holes profiles presents an inverted “U” type, and its profile morphology and slope distribution have geometric similarity. This distribution also reflected that, the interaction between the downward flow and the horseshoe vortex inside the scour hole leads to the formation of a cusp. Full article

(This article belongs to the Special Issue Water-Worked Bedload: Hydrodynamic and Mass Transport)

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Review

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16 pages, 931 KiB

Open AccessReview

Impact of Unsteady Flow Events on Bedload Transport: A Review of Laboratory Experiments

by Magdalena M. Mrokowska and Paweł M. Rowiński

Water 2019, 11(5), 907; https://doi.org/10.3390/w11050907 - 29 Apr 2019

Cited by 25 | Viewed by 5342

Abstract

Recent advances in understanding bedload transport under unsteady flow conditions are presented, with a particular emphasis on laboratory experiments. The contribution of laboratory studies to the explanation of key processes of sediment transport observed in alluvial rivers, ephemeral streams, and river reaches below a dam is demonstrated, primarily focusing on bedload transport in gravel-bed streams. The state of current knowledge on the impact of flow properties (unsteady flow hydrograph shape and duration, flood cycles) and sediment attributes (bed structure, sediment availability, bed composition) on bedload are discussed, along with unsteady flow dynamics of the water-sediment system. Experiments published in recent years are summarized, the main findings are presented, and future directions of research are suggested. Full article

(This article belongs to the Special Issue Water-Worked Bedload: Hydrodynamic and Mass Transport)

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19 pages, 4013 KiB

Open AccessReview

Water-Worked Gravel Bed: State-of-the-Art Review

by Ellora Padhi, Subhasish Dey, Venkappayya R. Desai, Nadia Penna and Roberto Gaudio

Water 2019, 11(4), 694; https://doi.org/10.3390/w11040694 - 04 Apr 2019

Cited by 7 | Viewed by 3773

Abstract

In a natural gravel-bed stream, the bed that has an organized roughness structure created by the streamflow is called the water-worked gravel bed (WGB). Such a bed is entirely different from that created in a laboratory by depositing and spreading gravels in the experimental flume, called the screeded gravel bed (SGB). In this paper, a review on the state-of-the-art research on WGBs is presented, highlighting the role of water-work in determining the bed topographical structures and the turbulence characteristics in the flow. In doing so, various methods used to analyze the bed topographical structures are described. Besides, the effects of the water-work on the turbulent flow characteristics, such as streamwise velocity, Reynolds and form-induced stresses, conditional turbulent events and secondary currents in WGBs are discussed. Further, the results form WGBs and SGBs are compared critically. The comparative study infers that a WGB exhibits a higher roughness than an SGB. Consequently, the former has a higher magnitude of turbulence parameters than the latter. Finally, as a future scope of research, laboratory experiments should be conducted in WGBs rather than in SGBs to have an appropriate representation of the flow field close to a natural stream. Full article

(This article belongs to the Special Issue Water-Worked Bedload: Hydrodynamic and Mass Transport)

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