Caracterización hidrodinámica de la confluencia de Los Ríos Tercero (Ctalamochita) y Saladillo

Las confluencias están presentes en toda red de escurrimiento superficial de cuencas hidrográficas, y son puntos en los cuales se producen cambios significantes en la hidrodinámica aguas abajo del punto de encuentro, tanto en aspectos morfológicos como en los patrones de mezcla del flujo. El estudio de las confluencias incluye gran cantidad de simulaciones numéricas (Kirkil y Constantinescu, 2009; Miyawaki et. al, 2009) y estudio a escala de laboratorio (Biron et. al, 1996; Herrero et.al, 2010). Con respeto a estudios en campo, el estado del arte ha llegado a caracterizar la hidrodinámica en confluencias fluviales a través de valores medios, pero no se ha alcanzado a realizar un análisis de la evolución temporal y espacial de estructuras turbulentas presentes en la zona de mezcla. En la actualidad, la disponibilidad de modernas técnicas de medición con una elevada resolución espacial y temporal, permiten lograr una adecuada caracterización de la hidrodinámica en confluencias fluviales, no sólo de las variables medias sino también poder caracterizar escalas espaciales y temporales de estructuras turbulentas. La confluencia de los ríos Ctalamochita y Saladillo que da origen al río Carcarañá, es un punto de interés ya que las cuencas de los tributarios poseen características muy diferentes.Fil: Herrero, Horacio. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Estudios y Tecnología del Agua; Argentina.Fil: García, Carlos. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Estudios y Tecnología del Agua; Argentina.Fil: Ragessi, Matías. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Estudios y Tecnología del Agua; Argentina.Fil: Szupiany, Ricardo. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas. Centro Internacional de Estudios de Grandes Ríos; Argentina.Ingeniería Civi

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

Evaluación experimental de la hidrodinámica y procesos de mezcla en la confluencia de los ríos Tercero y Saladillo

En este trabajo se presenta la caracterización experimental in situ de la hidrodinámica y patrones de mezcla de una confluencia natural de flujos de diferente densidad de dos ríos de mediana escala. Para ello se implementaron y optimizaron modernas técnicas experimentales de medición de velocidad de flujo (Perfiladores de corriente acústicos Doppler – ADCP), visualización del flujo, y medición de conductividad del agua. Con ADCP se determinaron la batimetría, y los parámetros hidráulicos globales mientras que con el uso de técnicas de visualización del flujo se pudo identificar el tamaño de la zona de estancamiento y las características de la capa de mezcla. Además, con GPS diferencial de alta precisión se relevó la pendiente de la superficie del agua. Finalmente, mediante la medición de la conductividad eléctrica y temperatura del agua de los flujos de aproximación y en la interfase de mezcla aguas abajo de la confluencia, se determinó la longitud requerida para la mezcla transversal completa de ambas masas de agua. Los resultados obtenidos en este trabajo permitieron evaluar el patrón hidrodinámico y de mezcla más conveniente para modelar los principales procesos presentes en confluencias fluviales como la estudiada que presenta naturaleza compleja. La presencia de flujos de diferente densidad genera una mayor complejidad en los patrones hidrodinámicos y de mezcla observados.Fil: Herrero, Horacio. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Estudios y Tecnología del Agua; Argentina.Fil: García, Carlos M. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Estudios y Tecnología del Agua; Argentina.Fil: Patalano, Antoine. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Estudios y Tecnología del Agua; Argentina.Fil: Szupiany, Ricardo. Universidad Nacional del Litoral. Facultad de Ingeniería y Ciencias Hídricas. Centro Internacional de Estudios de Grandes Ríos; Argentina.Ingeniería Civi

Hydro-geomorphological and sedimentological processes along the major fluvial-lacustrine delta of the Paraná River (Argentina): Their role in floodplain construction

River-dominated sea deltas have been thoroughly studied by different authors. In these environments the interrelationships of the hydro-sedimentological variables between river, tides, and waves, among others, are the main factors controlling the delta formation. However, few studies have focused on the deltaic processes in river–lagoon environments and even fewer in large river floodplains (defined here as a fluvial-lacustrine delta, FLD) and their role in floodplain construction. This study provides a comprehensive and novel analysis approach combining satellite imagery treatment and aerial photographs with detailed field measurements of sediment samplers, cores, and acoustic techniques applied to quantify flow and discharge distribution along main, secondary, floodplain channels, and lagoon systems under different hydro-sedimentological conditions. All data allow a full description of deltaic processes and the main variables that control the evolution of the major FLD located along the Middle Paraná River floodplain (Argentina). These results show: (i) pre-existing local geology elements affect the deltaic processes; (ii) the hydro-sedimentological behaviour of the main channel and its connection with the floodplain channels and independent basin systems affects the delta evolution; (iii) the dynamics (temporally and spatially) of sediment transport input and the interaction with lagoons produce different delta front bars planform and composition; (iv) periods of mean and high water levels play a key role in delta evolution; and (v) the rapid vegetation growth above the formed bars favours the sedimentation of fine material, producing permanent changes and leading to floodplain construction. Particularly, our findings suggest a complex interrelationship between the different factors in this particular environment, such as hydrology, local geology, main/secondary and floodplain channels, sediment supply, sediment transport modes, vegetation, and free surface slopes. All these factors act together in a complex manner, providing unique features to the FLD system that could help us better understand the floodplains construction in large river systems worldwide.Fil: Dominguez Ruben, Lucas Gerardo. 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: 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: Ramonell, Carlos Guillermo. 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: Ru, Micaela Yamila. 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: García, Marcelo Horacio. University of Illinois. Urbana - Champaign; Estados Unido

The Acoustic Properties of Suspended Sediment in Large Rivers: Consequences on ADCP Methods Applicability

The use of echo-levels from Acoustic Doppler Current Profiler (ADCP) recordings has become more and more common for estimating suspended bed-material and wash loads in rivers over the last decade. Empirical, semi-empirical and physical-based acoustic methods have been applied in different case studies, which provided relationships between scattering particles features derived from samples (i.e., concentration and grain size) and corresponding backscattering strength and sound attenuation. These methods entail different assumptions regarding sediment heterogeneity in the ensonified volume (e.g., particle size distribution (PSD) and spatial concentration gradient). Our work was to compare acoustic backscatter and attenuation properties of suspended sediments, sampled in the rivers Parana and Danube that represented rather different hydro-sedimentological conditions during the surveys. The Parana represents a large sandy river, characterized through a huge watershed and the typical bimodal PSD of sediment in suspension, while the Danube represents in the investigated reach an exposed sand-gravel bed and clay-silt particles transported in the water column in suspension. Sand and clay-silt concentrations clearly dominate the analyzed backscattering strength in the rivers Parana and Danube, respectively, with an effect of PSD level of sorting in the latter case. This comparison clarifies the extent of assumptions made, eventually advising on the actual possibility of applying certain ADCP methods, depending on the expected concentration gradients and PSD of suspended sediment to be investigated

The role of discharge variability in determining alluvial stratigraphy

We illustrate the potential for using physics-based modeling to link alluvial stratigraphy to large river morphology and dynamics. Model simulations, validated using ground penetrating radar data from the Río Paraná, Argentina, demonstrate a strong relationship between bar-scale set thickness and channel depth, which applies across a wide range of river patterns and bar types. We show that hydrologic regime, indexed by discharge variability and flood duration, exerts a first-order influence on morphodynamics and hence bar set thickness, and that planform morphology alone may be a misleading variable for interpreting deposits. Indeed, our results illustrate that rivers evolving under contrasting hydrologic regimes may have very similar morphology, yet be characterized by marked differences in stratigraphy. This realization represents an important limitation on the application of established theory that links river topography to alluvial deposits, and highlights the need to obtain field evidence of discharge variability when developing paleoenvironmental reconstructions. Model simulations demonstrate the potential for deriving such evidence using metrics of paleocurrent variance

Fluvial organic carbon composition regulated by seasonal variability in lowland river migration and water discharge

Identifying drivers of seasonal variations in fluvial particulate organic carbon (POC) composition can aid sediment provenance and biogeochemical cycling studies. We evaluate seasonal changes in POC composition in the Río Bermejo, Argentina, a lowland river running ∼1,270 km without tributaries. Weekly POC concentration and isotopic composition from 2016 to 2018 show that during the wet season, increased lateral channel migration generates an influx of 13C-enriched and 14C-enriched floodplain-sourced material, overprinting the 13C-depleted and 14C-depleted headwater signature that is observed during the dry season. These findings demonstrate how channel morphodynamics can drive variability of POC composition in lowland rivers, and may modulate the composition of POC preserved in sedimentary archives

Linking hydro-morphology with invertebrate ecology in diverse morphological units of a large river-floodplain system

Interdisciplinary research in the fields of ecohydrology and ecogeomorphology is becoming increasingly important as a way to understand how biological and physical processes interact with each other in river systems. The objectives of the current study were 1) to determine changes in invertebrate community due to hydrological stages, 2) to link local physical features [flow configuration, sediment composition and morphological feature) with the ecological structure between and within dissimilar morphological units (meander and confluence), and 3) to determine the existence and the origin of bed hydro-geomorphic patches, determining their ecological structure. Results were discussed in the frame of prevailing ecological models and concepts. The study site extends over a floodplain area of the large Paraná River (Argentina), including minor and major secondary channels as well as the main channel. Overall results suggested that hydrodynamics was the driving force determining distribution patterns of benthic assemblages in the floodplain. However, while the invertebrates living in minor secondary channels seem to benefit from flooding, this hydrological phase had the opposite effect on organisms from the main and major secondary channels. We also found a clear linkage between physical features and invertebrate ecology, which caused a dissimilar fauna structure between and within the meander and the confluence. Furthermore, several sandy-patches were recorded in the confluence. These patches were colonized by the particular benthic assemblage recorded in the main channel, supported the view of rivers as patchy discontinua, under uncertain ecological equilibrium.Instituto de Limnología "Dr. Raúl A. Ringuelet