Transport of variable-density solute plumes in beach aquifers in response to oceanic forcing

Bakhtyar, Roham; Brovelli, Alessandro; Barry, David Andrew; Robinson, C. E.; Li, Ling

doi:10.1016/j.advwatres.2012.11.009

Cited by 73 publications

(42 citation statements)

References 49 publications

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“…Even neglecting reactions, both tide and wave-induced circulations and associated saltwater-freshwater mixing can considerably reduce organic contaminant concentrations at the seabed via dilution [Robinson et al, 2007b;Robinson et al, 2009;Geng et al, 2014]. [Zhang et al, 2002;Brovelli et al, 2007;Bakhtyar et al, 2013;Liu et al, 2016].…”

Section: Organic Contaminantsmentioning

confidence: 99%

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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214

148

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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: Organic Contaminantsmentioning

confidence: 99%

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

214

148

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“…These studies can be classified into two categories: field or laboratory experiments and analytical or numerical models. Field or laboratory experiments rely on measurements to delineate the hydrodynamics of near-shore aquifer systems (e.g., Westbrook et al 2005;Trefry et al 2007;Kuan et al 2012;Heiss and Michael 2014), whereas analytical or numerical models solve governing equations that can approximately reproduce system responses according to input parameter variations (Ataie-Ashtiania et al 1999, 2001Mao et al 2006;Werner and Lockington 2006;Li et al 2008;Bakhtyar et al 2013). The greatest challenges hindering most experimental approaches involve obtaining sufficient data for resolving detailed mechanisms of flow and transport among various scales of interest.…”

Section: Introductionmentioning

confidence: 99%

Effects of hydrogeological properties on sea-derived benzene transport in unconfined coastal aquifers

Tsai

et al. 2016

Environ Monit Assess

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This paper presents numerical investigations on quantifying the hydrodynamic effects of coastal environment factors, including tidal fluctuations, beach slopes, hydraulic conductivity, and hydraulic gradients on sea-derived benzene transport in unconfined coastal aquifers. A hydrologic transport and mixed geochemical kinetic/equilibrium reactions in saturated-unsaturated media model was used to simulate the spatial and temporal behaviors of the density flow and benzene transport for various hydrogeological conditions. Simulation results indicated that the tidal fluctuations lead to upper saline plumes (USPs) near the groundwater and seawater interfaces. Such local circulation zones trapped the seaward benzene plumes and carried them down in aquifers to the depth depending on the tide amplitudes and beach slopes across the coastal lines. Comparisons based on different tidal fluctuations, beach slopes, hydraulic conductivity, and hydraulic gradient were systematically conducted and quantified. The results indicated that areas with USPs increased with the tidal amplitude and decreased with the increasing beach slope. However, the variation of hydraulic conductivity and hydraulic gradient has relatively small influence on the patterns of flow fields in the study. The increase of the USP depths was linearly correlated with the increase of the tidal amplitudes. The benzene reactive transport simulations revealed that the plume migrations are mainly controlled by the local flow dynamics and constrained in the USP circulation zones. The self-cleaning process of a coastal aquifer is time-consuming, typically requiring double the time of the contamination process that the benzene plume reach the bottom of a USP circulation zone. The presented systematic analysis can provide useful information for rapidly evaluating seaward contaminants along a coastal line with available hydrogeological properties.

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“…In spite of its significance, detailed simulation of combined waves and tides is not often conducted. This is because hydrodynamics of waves and tides are complex and act on different time scales (Xin et al 2010, Bakhtyar et al 2013a. Foreshore profile changes and sediment concentration for cases with different tidal ranges are given in Fig.…”

Section: Effect Of Tide and Wave Characteristics On Nearshore Morphodmentioning

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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Transport of variable-density solute plumes in beach aquifers in response to oceanic forcing

Cited by 73 publications

References 49 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

Effects of hydrogeological properties on sea-derived benzene transport in unconfined coastal aquifers

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

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