Numerical experiments on interactions between wave motion and variable-density coastal aquifers

Bakhtyar, Roham; Barry, David Andrew; Brovelli, Alessandro

doi:10.1016/j.coastaleng.2011.09.001

Cited by 29 publications

(27 citation statements)

References 51 publications

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“…Apart from this study and a few others including laboratory experiments [Boufadel et al, 2007;Heiss et al, 2015;Malott et al, 2016;Sous et al, 2016;Turner et al, 2016;Malott et al, 2017], investigations of wave-induced water exchange and groundwater dynamics have mostly been based on numerical simulations due to the challenge of measuring wave-induced groundwater flows in the field, including how to decouple wave and tide effects. Simulation of wave hydrodynamics coupled with densitydependent groundwater flow is computationally challenging but has been attempted by Bakhtyar et al [2012] and Geng et al [2014], who solved the Reynolds-Averaged Navier-Stokes (RANs) equations to simulate wave motion across a permeable beach surface. Both studies illustrate the 20 complexity of wave-induced groundwater flows induced by individual waves with Bakhtyar et al [2012] also demonstrating the additional impact of waves on beach morphology changes (e.g., wave-driven erosion/accretion).…”

Section: Wavesmentioning

confidence: 99%

“…Simulation of wave hydrodynamics coupled with densitydependent groundwater flow is computationally challenging but has been attempted by Bakhtyar et al [2012] and Geng et al [2014], who solved the Reynolds-Averaged Navier-Stokes (RANs) equations to simulate wave motion across a permeable beach surface. Both studies illustrate the 20 complexity of wave-induced groundwater flows induced by individual waves with Bakhtyar et al [2012] also demonstrating the additional impact of waves on beach morphology changes (e.g., wave-driven erosion/accretion).…”

Section: Wavesmentioning

confidence: 99%

“…The dynamics of this rapid infiltration-exfiltration have been studied with respect to its effect on beach sediment transport and coastal morphology [e.g., Turner and Nielsen, 1997;Horn et al, 1998;Masselink and Hughes, 1998;Turner and Masselink, 1998;Baldock et al, 2001;Elfrink and Baldock, 2002;Horn, 2006;Bakhtyar et al, 2012]. Heiss et al…”

Section: Wavesmentioning

confidence: 99%

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Groundwater dynamics in subterranean estuaries of coastal unconfined aquifers: Controls on submarine groundwater discharge and chemical inputs to the ocean

Robinson¹,

Xin²,

Santos³

et al. 2018

Advances in Water Resources

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Sustainable coastal resource management requires sound understanding of interactions between coastal unconfined aquifers and the ocean as these interactions influence the flux of chemicals to the coastal ocean and the availability of fresh groundwater resources. The importance of submarine groundwater discharge in delivering chemical fluxes to the coastal ocean and the critical role of the subterranean estuary (STE) in regulating these fluxes is well recognized. STEs are complex and dynamic systems exposed to various physical, hydrological, geological, and chemical conditions that act on disparate spatial and temporal scales. This paper provides a review of the effect of factors that influence flow and salt transport in STEs, evaluates current understanding on the interactions between these influences, and synthesizes understanding of drivers of nutrient, carbon, greenhouse gas, metal and organic contaminant fluxes to the ocean.Based on this review, key research needs are identified. While the effects of density and tides are well understood, episodic and longer-period forces as well as the interactions between multiple influences remain poorly understood. Many studies continue to focus on idealized nearshore aquifer systems and future work needs to consider real world complexities such as geological heterogeneities, and non-uniform and evolving alongshore and cross-shore morphology. There is also a significant need for multidisciplinary research to unravel the interactions between physical and biogeochemical processes in the STE, as most existing studies treat these processes in isolation. Better understanding of this complex and dynamic system can improve sustainable management of coastal water resources under the influence of anthropogenic pressures and climate change.

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Section: Wavesmentioning

confidence: 99%

Section: Wavesmentioning

confidence: 99%

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Groundwater dynamics in subterranean estuaries of coastal unconfined aquifers: Controls on submarine groundwater discharge and chemical inputs to the ocean

Robinson¹,

Xin²,

Santos³

et al. 2018

Advances in Water Resources

Self Cite

195

138

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“…Two major parameters that determine the beach type are sediment grain size and beach slope (Miles et al 2006, Bakhtyar et al 2012a. Numerical simulations were run for different beach slopes and for a range from coarse to fine sand beaches (cases 1, 16-20).…”

Section: Influence Of Beach Characteristics On Nearshore Morphologymentioning

confidence: 99%

Impacts of wave and tidal forcing on 3D nearshore processes on natural beaches. Part II: Sediment transport

Bakhtyar¹,

Dastgheib²,

Roelvink³

et al. 2016

Ocean Systems Engineering

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Abstract. This is the second of two papers on the 3D numerical modeling of nearshore hydro-and morphodynamics. In Part I, the focus was on surf and swash zone hydrodynamics in the cross-shore and longshore directions. Here, we consider nearshore processes with an emphasis on the effects of oceanic forcing and beach characteristics on sediment transport in the cross-and longshore directions, as well as on foreshore bathymetry changes. The Delft3D and XBeach models were used with four turbulence closures (viz., k-ε, k-L, ATM and H-LES) to solve the 3D Navier-Stokes equations for incompressible flow as well as the beach morphology. The sediment transport module simulates both bed load and suspended load transport of non-cohesive sediments. Twenty sets of numerical experiments combining nine control parameters under a range of bed characteristics and incident wave and tidal conditions were simulated. For each case, the general morphological response in shore-normal and shore-parallel directions was presented. Numerical results showed that the k-ε and H-LES closure models yield similar results that are in better agreement with existing morphodynamic observations than the results of the other turbulence models. The simulations showed that wave forcing drives a sediment circulation pattern that results in bar and berm formation. However, together with wave forcing, tides modulate the predicted nearshore sediment dynamics. The combination of tides and wave action has a notable effect on longshore suspended sediment transport fluxes, relative to wave action alone. The model's ability to predict sediment transport under propagation of obliquely incident wave conditions underscores its potential for understanding the evolution of beach morphology at field scale. For example, the results of the model confirmed that the wave characteristics have a considerable effect on the cumulative erosion/deposition, cross-shore distribution of longshore sediment transport and transport rate across and along the beach face. In addition, for the same type of oceanic forcing, the beach morphology exhibits different erosive characteristics depending on grain size (e.g., foreshore profile evolution is erosive or accretive on fine or coarse sand beaches, respectively). Decreasing wave height increases the proportion of onshore to offshore fluxes, almost reaching a neutral net balance. The sediment movement increases with wave height, which is the dominant factor controlling the beach face shape.

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“…Consequently, understanding of the beach environment needs to take account of the interactions between fluid flow and sediment particles on the beach, especially the role of waves and tides on foreshore profile changes. Prediction of the evolution of the nearshore morphology relies on understanding of the main processes affecting sediment transport, i.e., the relationships between sediment transport and tidal, wave and swash motions (Larson et al 2004, 2012a.…”

Section: Introductionmentioning

confidence: 99%

Impacts of wave and tidal forcing on 3D nearshore processes on natural beaches. Part I: Flow and turbulence fields

Bakhtyar¹,

Dastgheib²,

Roelvink³

et al. 2016

Ocean Systems Engineering

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Abstract. The major objective of this study was to develop further understanding of 3D nearshore hydrodynamics under a variety of wave and tidal forcing conditions. The main tool used was a comprehensive 3D numerical model -combining the flow module of Delft3D with the WAVE solver of XBeach -of nearshore hydro-and morphodynamics that can simulate flow, sediment transport, and morphological evolution. Surf-swash zone hydrodynamics were modeled using the 3D Navier-Stokes equations, combined with various turbulence models (k-ε, k-L, ATM and H-LES). Sediment transport and resulting foreshore profile changes were approximated using different sediment transport relations that consider both bed-and suspended-load transport of non-cohesive sediments. The numerical set-up was tested against field data, with good agreement found. Different numerical experiments under a range of bed characteristics and incident wave and tidal conditions were run to test the model's capability to reproduce 3D flow, wave propagation, sediment transport and morphodynamics in the nearshore at the field scale. The results were interpreted according to existing understanding of surf and swash zone processes. Our numerical experiments confirm that the angle between the crest line of the approaching wave and the shoreline defines the direction and strength of the longshore current, while the longshore current velocity varies across the nearshore zone. The model simulates the undertow, hydraulic cell and rip-current patterns generated by radiation stresses and longshore variability in wave heights. Numerical results show that a non-uniform seabed is crucial for generation of rip currents in the nearshore (when bed slope is uniform, rips are not generated). Increasing the wave height increases the peaks of eddy viscosity and TKE (turbulent kinetic energy), while increasing the tidal amplitude reduces these peaks. Wave and tide interaction has most striking effects on the foreshore profile with the formation of the intertidal bar. High values of eddy viscosity, TKE and wave set-up are spread offshore for coarser grain sizes. Beach profile steepness modifies the nearshore circulation pattern, significantly enhancing the vertical component of the flow. The local recirculation within the longshore current in the inshore region causes a transient offshore shift and strengthening of the longshore current. Overall, the analysis shows that, with reasonable hypotheses, it is possible to simulate the nearshore hydrodynamics subjected to oceanic forcing, consistent with existing understanding of this area. Part II of this work presents 3D nearshore morphodynamics induced by the tides and waves.

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Numerical experiments on interactions between wave motion and variable-density coastal aquifers

Cited by 29 publications

References 51 publications

Groundwater dynamics in subterranean estuaries of coastal unconfined aquifers: Controls on submarine groundwater discharge and chemical inputs to the ocean

Groundwater dynamics in subterranean estuaries of coastal unconfined aquifers: Controls on submarine groundwater discharge and chemical inputs to the ocean

Impacts of wave and tidal forcing on 3D nearshore processes on natural beaches. Part II: Sediment transport

Impacts of wave and tidal forcing on 3D nearshore processes on natural beaches. Part I: Flow and turbulence fields

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