Morphodynamics and seismostratigraphy of a deep hole at tidal channel confluence

Ginsberg, Silvia Susana; Aliotta, Salvador; Lizasoain, Guillermo Omar

doi:10.1016/j.geomorph.2008.09.002

Cited by 19 publications

(10 citation statements)

References 35 publications

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“…The bed level rises at the bifurcations and drops at the downstream end into scour holes. Such scours are typical for suspended load‐dominated rivers (Ikeda, ) and are often found at channel junctions (Ferrarin et al., ; Ginsberg et al., ). Scours are common in flow diversions (Herrero et al., ; Önen & Agaccioglu, ) and chute cut‐offs (Herbertson & Fares, ).…”

Section: Discussionmentioning

confidence: 99%

Flow and Suspended Sediment Division at Two Highly Asymmetric Bifurcations in a River Delta: Implications for Channel Stability

Kästner

Hoitink

2019

JGR Earth Surface

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The division of sediment at river bifurcations results from the complex interaction between three‐dimensional flow, planform, and channel bed morphology, as well as the heterogeneity of the bed material. Sediment division processes cannot be incorporated in their full complexity in scale experiments and are difficult to reproduce with numerical models. Field measurements are thus necessary to advance our understanding of those processes in river deltas. However, such measurements are rare. We present measurements of the flow and sediment division at two tidally influenced bifurcations of the Kapuas River, a large sand‐bedded suspended load‐dominated river in West Kalimantan, Indonesia. At both bifurcations, a smaller channel branches off from the side of the main river, which makes the planform strongly asymmetric. The planform of both bifurcations has been stable at least since the end of the nineteenth century when the region was mapped for the first time. Based on our measurements, we explore possible factors that stabilize the bifurcations. We measure the flow velocities with a boat‐mounted acoustic velocity profiler and determine the sediment concentration from acoustic backscatter, calibrated against water samples. The side branch of the first bifurcation receives a proportionally lower fraction of sediment than water. In contrast, the side branch at the second bifurcation receives a proportionally higher fraction of sediment than water. A comparison of flow velocity and suspended sand concentration indicates that the bed material sorting strongly influences the division of sediment, in particular at one of the bifurcations, which is situated in a meander bend.

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Section: Discussionmentioning

confidence: 99%

Flow and Suspended Sediment Division at Two Highly Asymmetric Bifurcations in a River Delta: Implications for Channel Stability

Kästner

Hoitink

2019

JGR Earth Surface

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“…explained a similar phenomenon of confluence deposition [15]. They found that the river sediment was deflected back into the river by the flood tides, thus producing the sediment deposition on the scour hole's gentle side (downstream slope).…”

Section: Morphological Changesmentioning

confidence: 81%

“…When flow velocity fell below 0.8 m/s, deposition occurred in the confluence area. Using morpho-sedimentological and seismo-stratigraphic data, Silva et al explained a similar phenomenon of confluence deposition [15]. They found that the river sediment was deflected back into the river by the flood tides, thus producing the sediment deposition on the scour hole's gentle side (downstream slope).…”

Section: Morphological Changesmentioning

confidence: 95%

Understanding Morphodynamic Changes of a Tidal River Confluence through Field Measurements and Numerical Modeling

Xie

Yang

Lundström

et al. 2018

Water

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A confluence is a natural component in river and channel networks. This study deals, through field and numerical studies, with alluvial behaviors of a confluence affected by both river run-off and strong tides. Field measurements were conducted along the rivers including the confluence. Field data show that the changes in flow velocity and sediment concentration are not always in phase with each other. The concentration shows a general trend of decrease from the river mouth to the confluence. For a given location, the tides affect both the sediment concentration and transport. A two-dimensional hydrodynamic model of suspended load was set up to illustrate the combined effects of run-off and tidal flows. Modeled cases included the flood and ebb tides in a wet season. Typical features examined included tidal flow fields, bed shear stress, and scour evolution in the confluence. The confluence migration pattern of scour is dependent on the interaction between the river currents and tidal flows. The flood tides are attributable to the suspended load deposition in the confluence, while the ebb tides in combination with run-offs lead to erosion. The flood tides play a dominant role in the morphodynamic changes of the confluence.

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“…These authors indicate that under different tidal conditions, the dunes always have displayed an asymmetric profile with the lee side towards the Principal channel. On the other hand, according to Ginsberg et al (2009a) the morphological and seismic studies in the system Tres BrazasTierra Firme are also indicative of ebb dominance in both channels, although only in the inner part of Tres Brazas channel there is a significant availability of sandy sediment mobilized as bedload transport. This circulation pattern is evidenced by the formation of the dunes above mentioned.…”

Section: Estimation Of the Bedload Sediment Transport And Relationshimentioning

confidence: 96%

“…Medium dune is the most common bedform in various sites of different tidal channels of Bahía Blanca estuary (Aliotta et al, 2004;Lizasoain, 2007;Ginsberg et al, 2009b). In particular, the channel system of Tres Brazas-El Alambre (Ginsberg et al, 2009a) have been found these bedforms (L=8-10 m; H=0.4-0.6 m) on a relatively thin sand belt, in the inner sector of Tres Brazas channel. Also, they found large dunes (L=12 m and H=0.8 m) in the mouth of Tres Brazas channel with their crestlines very sinuous and barchanoid structure with low lateral continuity.…”

Section: Estimation Of the Bedload Sediment Transport And Relationshimentioning

confidence: 99%

Sediment Transport Circulation Pattern through Mesotidal Channels System

Ginsberg¹,

Aliotta²

2011

Sediment Transport

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Morphodynamics and seismostratigraphy of a deep hole at tidal channel confluence

Cited by 19 publications

References 35 publications

Flow and Suspended Sediment Division at Two Highly Asymmetric Bifurcations in a River Delta: Implications for Channel Stability

Flow and Suspended Sediment Division at Two Highly Asymmetric Bifurcations in a River Delta: Implications for Channel Stability

Understanding Morphodynamic Changes of a Tidal River Confluence through Field Measurements and Numerical Modeling

Sediment Transport Circulation Pattern through Mesotidal Channels System

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