Dynamics of river mouth deposits

Fagherazzi, Sergio; Edmonds, Douglas A.; Nardin, William; Leonardi, Nicoletta; Canestrelli, Alberto; Falcini, Federico; Jerolmack, D. J.; Mariotti, G.; Rowland, J. C.; Slingerland, Rudy

doi:10.1002/2014rg000451

Cited by 144 publications

(113 citation statements)

References 128 publications

(410 reference statements)

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“…However, in field settings, it is difficult to obtain a meaningful data set that covers the full evolution of a delta because these landforms evolve over large spatial and temporal scales. Instead, researchers utilize numerical models and laboratory experiments to investigate the controls on delta dynamics, which can then be related back to natural landscapes (Edmonds & Slingerland, ; Fagherazzi et al, ; Hoyal & Sheets, ; Kim et al, ; Kim & Jerolmack, ; Reitz et al, ). As a community, we rely heavily on physical and computational modeling of these important natural systems to understand how deltas form and evolve over time.…”

Section: Introductionmentioning

confidence: 99%

Laboratory Investigation on Effects of Flood Intermittency on Fan Delta Dynamics

2019

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To simplify the complex hydrological variability of flow conditions, experiments on delta evolution are often conducted using a representative channel‐forming flood flow and results are related to field settings using an intermittency factor, defined as the fraction of time in flood. Although this factor provides an approximation of dominant flow conditions and makes modeling deltas easier by turning their complex hydraulics into a single representative value, little is known about how this generalization affects delta processes. We conducted experiments with periodic flow conditions to determine the effects of intermittent discharges on fan deltas. For each run, the magnitude of floods was held constant, but the duration changed, thus varying the intermittency factor, between 1 and 0.2. Floods consisted of higher water and sediment discharge, while base flow periods had lower water discharge and sediment input ceased, causing the system to become erosional during these periods. We find that as the duration of floods decreases, the delta topset is larger in area with a shallower slope due to reworking on the topset during base flow conditions. During base flows, the experimental system adjusts toward a new equilibrium state that in turn acts as the initial condition for subsequent flood periods. These results suggest that the adjustment timescale is a factor in determining the behavior of deltas and their channels. We conclude that both periods of flood when most of the sediment is supplied to the system and periods of base flow when topset sediment is reworked contribute to delta dynamics.

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Section: Introductionmentioning

confidence: 99%

Laboratory Investigation on Effects of Flood Intermittency on Fan Delta Dynamics

2019

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“…When a river enters a standing body of water, its discharge and sediment load, previously confined to the channel, form a river mouth jet that gradually slows down and expands [ Bates , ; Wright , ; Canestrelli et al , ; Fagherazzi et al , ]. Hydrodynamically, river mouth jets are turbulent and bounded above and below by the free surface and bed friction, respectively [ Rowland et al , ; Canestrelli et al , ].…”

Section: Introductionmentioning

confidence: 99%

Alongshore sediment bypassing as a control on river mouth morphodynamics

et al. 2016

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River mouths, shoreline locations where fluvial and coastal sediments are partitioned via erosion, trapping, and redistribution, are responsible for the ultimate sedimentary architecture of deltas and, because of their dynamic nature, also pose great management and engineering challenges. To investigate the interaction between fluvial and littoral processes at wave-dominated river mouths, we modeled their morphologic evolution using the coupled hydrodynamic and morphodynamic model Delft3D-SWAN. Model experiments replicate alongshore migration of river mouths, river mouth spit development, and eventual spit breaching, suggesting that these are emergent phenomena that can develop even under constant fluvial and wave conditions. Furthermore, we find that sediment bypassing of a river mouth develops though feedbacks between waves and river mouth morphology, resulting in either continuous bypassing pathways or episodic bar bypassing pathways. Model results demonstrate that waves refracting into the river mouth bar create a zone of low alongshore sediment transport updrift of the river mouth, which reduces sediment bypassing. Sediment bypassing, in turn, controls the river mouth migration rate and the size of the river mouth spit. As a result, an intermediate amount of river discharge maximizes river mouth migration. The fraction of alongshore sediment bypassing can be predicted from the balance between the jet and the wave momentum flux. Quantitative comparisons show a match between our modeled predictions of river mouth bypassing and migration rates observed in natural settings.

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“…Edmonds and Slingerland, 2007;Wright, 1977). Extensive work has been done to predict initial flow and sedimentation patterns associated with turbulent jets entering basins (Fagherazzi et al, 2015). Our work seeks to extend this approach to systems with complex emergent topography and multiple interacting channels.…”

Section: Bathymetry and Flow Patterns On River-dominated Deltasmentioning

confidence: 99%

Measuring Subaqueous Progradation of the Wax Lake Delta with a Model of Flow Direction Divergence

Shaw¹,

Estep²,

Whaling³

et al. 2018

Preprint

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Abstract.Remotely sensed flow patterns can reveal the location of the subaqueous distal tip of a distributary channel on a prograding river delta. Morphodynamic feedbacks produce distributary channel tips that become shallower over their final reaches before becoming deeper over the unchannelized foreset. The flow direction field over this morphology tends to diverge 10 and then converge providing a diagnostic signature that can be captured in flow or remote sensing data. Twenty-one measurements from the Wax Lake Delta (WLD) in coastal Louisiana, and 317 measurements from numerically simulated deltas show that the transition from divergence to convergence occurs in a distribution that is centered just downstream of the channel tip, on average 132 m in the case of the WLD. With these data we validate the Flow Direction to Channel tips (FD2C) inverse model for remotely estimating subaqueous channel tip location. We apply this model to 33 remotely sensed images of 15 the WLD between its initiation in 1974 and 2016. We find that the distributaries grew unevenly, 6 of the primary channels grew at rates of 60-80 m/yr while one grew at 116 m/yr. We also estimate the growth rate of the total area enclosed by the subaqueous delta platform to be 1.83 km 2 /yr with no obvious rate changes over time.

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Dynamics of river mouth deposits

Cited by 144 publications

References 128 publications

Laboratory Investigation on Effects of Flood Intermittency on Fan Delta Dynamics

Laboratory Investigation on Effects of Flood Intermittency on Fan Delta Dynamics

Alongshore sediment bypassing as a control on river mouth morphodynamics

Measuring Subaqueous Progradation of the Wax Lake Delta with a Model of Flow Direction Divergence

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