Morphology, flow structure, and suspended bed sediment transport at two large braid-bar confluences

Mid-channel bars and their associated confluences are key morphodynamic nodes within braided rivers, with past studies having investigated the morphodynamics of small natural channels or laboratory models with relatively low width/depth (W/D) ratios, typically at <10. This paper investigates the morphology, suspended bed sediment distribution, and flow structure at two large braid bar confluences in the Río Parana (Argentina), wherein W/D ratios are much higher (approaching 100) than in smaller channels. The results highlight the significant control of the cross-sectional distribution of downstream flow velocity on confluence flow, suspended bed sediment concentration, and morphodynamics and indicate that this factor may become progressively more significant with increasing channel scale and W/D ratio, particularly when simple discharge (or momentum) ratios between the incoming flows are used to explain the flow dynamics. Additionally, secondary flow cells, often proposed to occupy a large part of the channel width in small river channel confluences, are only identified in relatively small portions of the channel width at these larger spatial scales. Such a restriction seems related to the generative mechanisms of secondary flows at these higher W/D ratios, which are likely to be dominated by turbulence generated along the mixing layer between the two flows and topographic influences that limit the spatial extent of these effects. This paper highlights the importance of these findings with respect to the flow and sediment dynamics of large channel confluences.Fil: Szupiany, Ricardo Nicolas. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas. Departamento de Hidráulica; ArgentinaFil: Amsler, Mario Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Parsons, Daniel R.. University Of Leeds - School Of Earth And Environ.; Reino UnidoFil: Best, James L.. University Of Illinois - Dept. Of Geology And Geography; Estados Unido

Meander Statistics Toolbox (MStaT): a toolbox for geometry characterization of bends in large meandering channels

This contribution presents MStaT, a wavelet-based open-source software developed to provide a detailed characterization of large meandering river morphodynamics. MStaT integrates three independent modules: (i) meandering morphometrics module; (ii) migration module; and (iii) confluence module. MStaT delivers a short and medium-term framework to analyze the river centerline and valley-meandering channel interrelationship at low computational cost. It provides quantitative information on the spatial distribution of the arc-wavelength, migration rates, cutoffs events, and tributary channels influences. Data are presented through a user-friendly graphical user interface that makes the output interpretation easier, and that is freely available to the communities of river morphodynamics scientists and engineers.Fil: Dominguez Ruben, Lucas Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas; ArgentinaFil: Naito, Kensuke. Universidad de Ingenieria y Tecnologia; PerúFil: Gutierrez, Ronald Roger. Pontificia Universidad Católica de Perú; PerúFil: Szupiany, Ricardo Nicolas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas; ArgentinaFil: Abad, Jorge Darwin. Universidad de Ingenieria y Tecnologia; Perú. Red Yaku; Per

Extremes in dune preservation: controls on the completeness of fluvial deposits

Understanding sedimentary preservation underpins our ability to interpret the ancient sedimentary record and reconstruct palaeoenvironments and palaeoclimates. Dune sets are ubiquitous in preserved river deposits and are typically interpreted based on a model that that describes the recurrence of erosion in a vertical sequence, but without consideringspatial variability. However, spatial variability in flow and sediment transport will change the recurrence of erosion, and therefore dune preservation. In order to better understand the limits of these Interpretations and outline the causes of potential variability in preservation potential, this paper reviews existing work and presents new observations of an extreme end-member of dune preservation: ?form-sets?, formed by dunes in which both stoss- and lee- slopes are preserved Intact. These form-sets do not conform to models that are based on the recurrence of erosion, since erosion does not recur in their case, and can therefore be used to evaluate the assumptions that underpin sedimentary preservation. New Ground Penetrating Radar data from the Río Paraná, Argentina, show dune fields that are buried intact within larger scale barforms. These trains of form-sets are up to 300 m in length, are restricted to unit-bar troughs in the upper 5 m of the channel deposits, occur in >5% of the mid-channel bar deposits, show reactivation surfaces, occur in multiple levels, and match the size of average-flow dunes. A review of published accounts of form-sets highlights a diversity of processes that can be envisaged for their formation: i) abandonment after extreme floods, ii) slow burial of abandoned dune forms by cohesive clay in sheltered bar troughs and meander-neck cut-offs, iii) fast burial by mass-movement processes, and iv)climbing of dune sets due to local dominance of deposition over dune migration.Analysis of these new and published accounts of form-sets and their burial processes highlights that form-sets need not be indicative of extreme floods. Instead, form-sets are closely associated with surrounding geomorphology such as river banks, meander-neck cutoffs,and bars because this larger-scale context controls the local sediment budget and the nature of recurrence of erosion. Locally enhanced preservation by the ?extreme? dominance of deposition is further promoted by finer grain sizes and prolonged changes in flow stage. Such conditions are characteristic, although not exclusive, of large lowland rivers such as the Río Paraná. The spatial control on dune preservation is critical: although at-a-point models adequately describe near-horizontal sets of freely migrating dunes in uniform flows, they are unsuitable for inclined dune co-sets and other cases where multiple scales of bedforms interact. Spatial and temporal variations in flow and sediment transport betweenthe thalweg and different positions on larger bar-forms can change the preservation potential of dunes within river channels. Therefore, dune set thickness distributions are likely grouped in larger-scale units that reflect both formative dune geometries and bar-scale variations inpreservation potential. The multi-scale dynamics of preservation highlighted herein also provides a useful comparison for other sedimentary systemsFil: Reesink, Arnold J.. University Of Binghamton; Estados UnidosFil: Van den Berg, J. H.. University of Utrecht; Países BajosFil: Parsons, Daniel R.. University Of Hull; Reino UnidoFil: Amsler, Mario Luis. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Best, James L.. University of Illinois. Urbana - Champaign; Estados UnidosFil: Hardy, Richard J.. University Of Durham; Reino UnidoFil: Orfeo, Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Szupiany, Ricardo Nicolas. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas; Argentin

Acoustic Instruments for Mean Flow Characterization in Field Conditions: Acoustic Doppler Current Profilers (ADCP)

This two-volume book is a comprehensive guide to designing, conducting and interpreting experiments in a broad range of topics associated with hydraulic engineering. It is the first substantial effort in hydraulic engineering to assemble in one place descriptions of all the components of experimentation along with a concise outline of essential theory to highlight the intrinsic connection between analytical and experimental research and illustrate the need for their complementary use. Providing end-to-end guidance to support experimentalists is long overdue, as most of the information can only be found in scientific papers or specialized monographs on laboratory and fieldwork practice. The book was prepared for college faculty, researchers, practitioners, and students involved in hydraulics experiments. Written by a team of more than 45 authors well-experienced in hydraulics experimentation, the book takes into account experiments performed under a range of conditions, including well-equipped and -staffed laboratories, and laboratories lacking aspects of advanced instrumentation and expertise. The book could serve as a textbook on hydraulics experiments. Its style is intentionally concise and makes frequent use of convenient summaries, tables and figures to present information. The writers provide specific guidance on methods and instruments currently used in hydraulics experiments, and emphasizes new and emerging measurement technologies and analysis methods. Extensive references enable interested readers to further explore details on each topic. Although the book focuses primarily on laboratory experiments, including hydraulic modelling, it also applies to fieldwork of varying complexity and accessibility.Fil: Szupiany, Ricardo Nicolas. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas. Departamento de Hidráulica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Garcia, Carlos M.. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Estudios Tecnológicos Sobre el Agua; ArgentinaFil: Oberg, Kevin. United States Geological Survey; Estados Unido

Confluence analysis at basin scale in a tropical bedrock river – The Ivaí River, Southern Brazil

River confluences are sites that operate with complex interactions between material and energy, provided by the combination of different flow patterns that present continuous changes in flow structure and sediment transport. In addition, river confluences have intrinsic ecological value, where biophysical processes and ecosystem services may be concentrated. This study aimed to analyze the morphology, flow structure, and hydrosedimentary interaction along tributary-trunk river confluences in a bedrock-alluvial plateau basin. The study included a field investigation into the mixed bedrock-alluvial basin of morphology, bed sediments, and hydrologic condition (including the flow structure) of 29 confluences to identify and analyze the similarities and differences between these confluences at the basin scale. For example, we considered the Ivaí River Basin, a medium-sized dam-free river that exhibits a mixed bedrock-alluvial bed and heterogeneity in both geology and longitudinal profile. Our findings show that the flow structure and morphology are conditioned by geological aspects, and the composition of the flow is extremely affected by the Ivaí River. In general, our results presented distinct differences from field-based data described in the literature for alluvial river confluences.Fil: Dos Santos, V.. Centre National de la Recherche Scientifique; FranciaFil: Stevaux, J. C.. Universidade Federal do Mato Grosso do Sul; BrasilFil: Szupiany, Ricardo Nicolas. Universidad Nacional del Litoral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentin

Hydrodynamics and sediment transport in an estuary with an abrupt depth step

The hydrodynamic patterns resulting from the combination of tide flow, riverine discharge and bathymetry and their effects on water circulation and sediment transport are studied to assess the impact of geomorphic changes in the Quequén Grande River estuary (Buenos Aires, Argentina). A depth step located at about 2 km from the sea, created by dredging to provide favourable navigational conditions in the harbour, induces different flow patterns in the deeper and shallow estuarine parts, creating an attractive system to study. The main purpose of this paper is to report key physical features of this water system and the results of detailed longitudinal and transverse measurements of velocity and backscatter intensity. The data reveal the selective settling of suspended sediments in the harbour and a net loss of sediments to the sea. The effects of local severe storms that cause an intense tidal intrusion and mixing as well as a stronger ebb flow and seiches are also described.Fil: Pereyra, Mariana Gisele. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Flujos Geofisicos y Ambientales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Marino, Beatriz Maria. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Flujos Geofisicos y Ambientales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Szupiany, Ricardo Nicolas. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas; ArgentinaFil: Thomas, Luis Pablo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Flujos Geofisicos y Ambientales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentin

Characterisation of the suspended particulate matter in a stratified estuarine environment employing complementary techniques

The ability to predict the sediment and nutrient circulation within estuarine waters is of significant economic and ecological importance. In these complex systems, flocculation is a dynamically active process that is directly affected by the prevalent environmental conditions. Consequently, the floc properties continuously change, which greatly complicates the characterisation of the suspended particle matter (SPM). In the present study, three different techniques are combined in a stratified estuary under quiet weather conditions and with a low river discharge to search for a solution to this problem. The challenge is to obtain the concentration, size and flux of suspended elements through selected cross-sections using the method based on the simultaneous backscatter records of 1200 and 600 kHz ADCPs, isokinetic sampling data and LISST-25X measurements. The two-ADCP method is highly effective for determining the SPM size distributions in a non-intrusive way. The isokinetic sampling and the LISST-25X diffractometer offer point measurements at specific depths, which are especially useful for calibrating the ADCP backscatter intensity as a function of the SPM concentration and size, and providing complementary information on the sites where acoustic records are not available. Limitations and potentials of the techniques applied are discussed.Fil: Thomas, Luis Pablo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Marino, Beatriz Maria. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Szupiany, Ricardo Nicolas. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gallo, Marcos N.. Universidade Federal do Rio de Janeiro; Brasi

Large meandering bends with high width-to-depth ratios: insights from hydro-sedimentological processes

Morphodynamics and hydro-sedimentological processes in meandering rivers are one of the most complex phenomena observed in alluvial channels. Because of the complex nature of the interaction between flow structure, morphology, sediment transport, and bank roughness, a better understanding of these morphological units is needed, particularly for low-gradient rivers characterized by large meandering bends with high width-to-depth ratios. The present research provides an accurate description of the interaction between suspended bed-sediment transport, flow structure, and bed morphology on three consecutive bends characterized by width-to-depth ratios higher than 50. The study focuses on a selected reach of the Colastiné River, which is a secondary channel of the Paraná River, Argentina. Acoustic measurement techniques with high spatial-time resolution were employed during two different events - a bankfull and a medium-flow stage event - to capture the three-dimensionality of the flow velocity, suspended bed-sediment transport, and variations in bed morphology. Although the core of maximum velocity shifts from bank to bank at the bend entrance, following the thalweg shifting, the suspended bed-sediment concentration remains in the center of the channel because of the strong influence of the secondary currents and the bed morphology. Two types of secondary flows are well-defined in the cross section: a unidirectional flow toward the outer bank generated by the topographic steering effect along the point bar, and the classical helical motion confined to the thalweg zone. Close to the outer bank, the core of maximum velocity shifts toward the center of the channel because of the presence of macro-roughness induced by banklines and downed trees, which in turn generate high turbulence patterns along the outer bank. The bed morphology shows an extended point bar occupying almost half of the channel width (in the cross section apex) and spreading downstream to the entrance of the following bend. The thalweg shows an abrupt change from bank to bank, producing high curvature at each bend entrance. The findings reported herein show a lack of correlation between the cores of maximum velocity and suspended bed sediment, exhibiting different behaviors than those observed in smaller alluvial channels with lower width-to-depth ratios.Fil: Dominguez Ruben, Lucas Gerardo. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Szupiany, Ricardo Nicolas. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Tassi, Pablo. No especifíca;Fil: Vionnet, Carlos Alberto. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentin

Evaluation of image velocimetry for the quantification of flow discharge and characterization of the flow field in the Pilcomayo River

The Pilcomayo River basin is shared by three countries: Argentina, Bolivia and Paraguay, which rises great challenges socially, economically and environmentally. First, from the social point of view, there are more than 20 ethnic groups living in the basin area. Second, economic demand is high in this region although the river basin is located far away from the major economic centers in each country. Environmentally several aspects can be considered. In the upper basin mining and oil-gas activities have been intense for centuries. In the middle basin the river has a high lateral mobility and sediment transport from the higher basin to the lower one gives the river a characteristic behavior of stream blockage which leads to the formation of various wetlands with high biodiversity. This second edition presents a compilation and analysis of major hydraulic problems encountered in the basin. These problems involve the high mobility of the channel, the possibility of changing course during floods, and serious difficulties in the distribution of water and sediment between Argentina and Paraguay.Fil: Patalano, Antoine. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Estudios Tecnológicos Sobre el Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Szupiany, Ricardo Nicolas. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Garcia, Carlos Marcelo. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Estudios Tecnológicos Sobre el Agua; ArgentinaFil: Testa Tacchino, Alejo Juan Sebastián. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Estudios Tecnológicos Sobre el Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Obtuse-angle vs. confluent sharp meander bends: insights from the Paraguay-Cuiabá confluence in the tropical Pantanal wetlands, Brazil

River confluences are notable features in the drainage system with complex hydrodynamics, bed morphology, sediment transport, and mixing processes. Junction planform plays a pivotal role in the confluence hydrodynamics. However, most investigations have concentrated on the junction of two straight channels, and few studies have focused on confluent meander bends or obtuse-angle confluences. Here we analyze a confluence with an obtuse-angle planform–the tributary enters the confluence at an angle higher than 180°–that abruptly curves to join the main river. In the Pantanal wetlands, the strong flood wave is responsible for significant variations of the discharge and momentum-flux ratios within the confluence. Consequently, the Paraguay-Cuiabá confluence is able to shift from an obtuse-angle working mode to a confluent meander bend working mode according to the hydrological conditions. When the momentum ratio is greater than 1 (Mr>1), the confluence works as an obtuse-angle junction, whereas when the ratio is less than 1 (Mr<1), the observed behaviors correspond to a confluent meander bend.Fil: Luz, Leandro D.. UNIVERSIDADE ESTADUAL DE MARINGÁ (UEM);Fil: Szupiany, Ricardo Nicolas. Universidad Nacional del Litoral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Parolin, Mauro. Universidade Federal do Paraná; BrasilFil: Silva, Aguinaldo. Universidade Federal do Mato Grosso do Sul; BrasilFil: Stevaux, José C.. Universidade Federal do Mato Grosso do Sul; Brasi