Stability of delta distributary networks and their bifurcations

Edmonds, Douglas A.; Slingerland, Rudy

doi:10.1029/2008wr006992

Cited by 122 publications

(165 citation statements)

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“…This means that despite the variation in the ratio of depth and/or width, the flow tends to have the same mean velocity in both branches. Also, both FlowRCM and Delft3D predict a water surface gradient in the shallower branch that is significantly higher than the one in the deeper branch, consistent with field observations by Edmonds and Slingerland (2008). An example of flow field and water surface elevation (test C3) is plotted in Fig.…”

Section: Test 2: Flow Around a Mouth Barsupporting

confidence: 69%

“…Nevertheless, the gradient in the surface profile is essential to water motion in deltaic environments (Edmonds and Slingerland, 2008). As mentioned in the previous section, FlowRCM estimates the water surface based on the assumption of a 1-D surface profile along flow streamlines.…”

Section: Test 1: Backwater Profile In a Straight Channelmentioning

confidence: 99%

“…4 and 5 such irregularities do not affect the ability of the model to reproduce key hydrodynamic features. network (Edmonds and Slingerland, 2008;Edmonds et al, 2010;Kleinhans et al, 2008Kleinhans et al, , 2013. We use a simple and idealized bifurcation topography to test the response of FlowRCM to bifurcation asymmetry, e.g., changes in width and/or depth ratio of the two downstream branches.…”

Section: Test 2: Flow Around a Mouth Barmentioning

confidence: 99%

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A reduced-complexity model for river delta formation – Part 2: Assessment of the flow routing scheme

et al. 2015

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Abstract. In a companion paper (Liang et al., 2015) we introduced a reduced-complexity model (RCM) for river delta formation, developed using a parcel-based "weighted random walk" method for routing water and sediment flux. This model (referred to as DeltaRCM) consists of a flow routing scheme as the hydrodynamic component (referred to as FlowRCM) and a set of sediment transport rules as the morphodynamic component. In this work, we assess the performance of FlowRCM via a series of hydrodynamic tests by comparing the model outputs to Delft3D and theoretical predictions. These tests are designed to reveal the capability of FlowRCM to resolve flow field features that are critical to delta dynamics at the level of channel processes. In particular, we focus on (1) backwater profile, (2) flow around a mouth bar, (3) flow through a single bifurcation, and (4) flow through a distributary channel network. We show that while the simple rules are not able to reproduce all fine-scale flow structures, FlowRCM captures flow field features that are essential to deltaic processes such as bifurcations and avulsions, the partitioning of flux between channels and inundated islands, and the instability of flux distribution at channel mouths which is responsible for mouth-bar growth. Finally, we discuss advantages and limitations of FlowRCM and identify environments most suitable for it.

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Section: Test 2: Flow Around a Mouth Barsupporting

confidence: 69%

Section: Test 1: Backwater Profile In a Straight Channelmentioning

confidence: 99%

Section: Test 2: Flow Around a Mouth Barmentioning

confidence: 99%

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A reduced-complexity model for river delta formation – Part 2: Assessment of the flow routing scheme

et al. 2015

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“…Physically conceptual models to predict the hydraulic and geomorphic conditions for an avulsion process were developed by many authors (Mackey and Bridge, 1995;Slingerland and Smith, 1998;Barbe et al, 2000;Winer and Raphelt, 2005;Edmonds and Slingerland, 2008;Letter et al, 2008). They showed that the avulsion depends on the main channel to former meander channel bed slopes ratio, the bed grain size, water surface elevation at the bifurcation areas, the diversion angle, etc.…”

Section: Local Control Factors Governing the Distribution Of Flow Energymentioning

confidence: 99%

Contrasted sediment processes and morphological adjustments in three successive cutoff meanders of the Danube delta

Duţu

Provansal

Coz³

et al. 2014

Geomorphology

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Since the 1980s intensive anthropogenic disturbances have affected the channel of the St. George branch, the southern distributary of the Danube River. The meander cutoff program since [1984][1985][1986][1987][1988] induced different hydrosedimentary impacts on the local distribution of river flow velocities, discharge, and sediment fluxes between the former meanders and the man-made canals (Ichim and Radoane, 1986;Popa, 1997;Panin, 2003). This paper selects three large cutoff meander reaches of the St. George branch (the Mahmudia,

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“…Furthermore, these studies considered isolated bifurcations, whereas in natural delta networks the bifurcations are interconnected. For instance, the presence of a bifurcation produces a backwater slope that extends upstream [Edmonds and Slingerland, 2008], and its absence could affect the water surface slopes of other reaches, thereby propagating the original perturbation throughout the entire delta network.[5] To address these shortcomings, this paper presents the first numerical study of the response of distributaries within a self-formed, river-dominated delta to changes in Q at the delta head. Results show a threshold behavior.…”

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confidence: 99%

Response of river‐dominated delta channel networks to permanent changes in river discharge

Edmonds

Slingerland

Best

et al. 2010

Geophysical Research Letters

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[1] Using numerical experiments, we investigate how river-dominated delta channel networks are likely to respond to changes in river discharge predicted to occur over the next century as a result of environmental change. Our results show for a change in discharge up to 60% of the initial value, a decrease results in distributary abandonment in the delta, whereas an increase does not significantly affect the network. However, an increase in discharge beyond a threshold of 60% results in channel creation and an increase in the density of the distributary network. This behavior is predicted by an analysis of an individual bifurcation subject to asymmetric water surface slopes in the bifurcate arms. Given that discharge in most river basins will change by less than 50% in the next century, our results suggest that deltas in areas of increased drought will be more likely to experience significant rearrangement of the delta channel network. Motivation[2] An immediate impact of climate change and human modifications to river catchments is that the long-term average discharge of most rivers will change appreciably over the next century [Nohara et al., 2006;Palmer et al., 2008]. On rivers that terminate in marine or lacustrine basins, this hydrological change also will impact their deltas, and yet no framework exists for predicting the adjustments deltas may undergo as discharge changes. Relative sea-level rise is already threatening the world's deltas [Blum and Roberts, 2009;Syvitski et al., 2009], and that problem could be further compounded if permanent changes in discharge also dramatically alter delta landscapes, which provide wetlands, biodiversity,, and homes to a significant part of the world's population [Coleman, 1988;Day et al., 2007]. Studies to date have focused on identifying which deltas are at risk [Day et al., 1995;Ericson et al., 2006] and how they might respond to perturbations such as sea-level rise [Jerolmack, 2009]. But, how deltaic distributary networks will respond to changes in river discharge remains unknown.[3] As the long-term average river discharge (Q) changes, the most dramatic response of a deltaic channel network, apart from a full avulsion caused by delta-lobe switching [Coleman, 1988], is abandonment or initiation of distributary channels. This scenario could be expected because the number of bifurcations in a distributary network correlates positively with the input Q and inversely with the power in the marine environment [Syvitski and Saito, 2007]. However, it is unclear whether an individual delta's response to changes in Q would follow the same trend between Q and channel number observed from the Syvitski and Saito delta compilation.[4] Past work has shown that the splitting of discharges at channel bifurcations is subject to fairly stringent stability conditions. Two distributaries with identical downstream boundary conditions and a given upstream Shields stress (Q) distribute water and sediment asymmetrically because this is a stable equilibrium configuration [Wang et al., 1995;S...

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Stability of delta distributary networks and their bifurcations

Cited by 122 publications

References 40 publications

A reduced-complexity model for river delta formation – Part 2: Assessment of the flow routing scheme

A reduced-complexity model for river delta formation – Part 2: Assessment of the flow routing scheme

Contrasted sediment processes and morphological adjustments in three successive cutoff meanders of the Danube delta

Response of river‐dominated delta channel networks to permanent changes in river discharge

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