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Abstract Interactions between surface flows and groundwater in beaches can influence erosion and accretion, wave overtopping, groundwater levels and salinization, and transport of nutrients and pollutants. Laboratory experiments using transparent crushed quartz and optically matched mineral oil as proxies for sand and water allow the degree of saturation to be computed at pore‐scale (0.7 mm resolution) enabling detailed investigations of the wave runup driven infiltration into a beach in a wave flume for a range of slopes and flow boundary conditions. The evolution of the wetting front resulting from wave runup on an initially unsaturated beach is described in detail, including the formation of an infiltration wedge in the subsurface of the swash zone and the wave‐driven rise in fluid elevation inside the beach. The elevation of the runup for each event is found to be related closely to the saturation of the beach face, reaching an equilibrium state once the subsurface in the swash zone reaches capacity. The back wall boundary condition in the flume has a significant role in how subsurface flows increase saturation within the beach, especially with boundary head elevations greater than the initial phreatic surface. The results of these novel experimental observations are used to develop dimensionless relationships between the surface wave runup and the subsurface saturation rates. To improve monitoring and interpretation of future coastal groundwater studies, three distinct cross‐shore regimes are defined for assessing change in subsurface fluid elevation in the beach. 

This resource contains the data required to reproduce the results of Heiss et al. (2022). Heiss, J. W., Mase, B., & Shen, C. (2022). Effects of Future Increases in Tidal Flooding on Salinity and Groundwater Dynamics in Coastal Aquifers. Water Resources Research, 58. https://doi.org/10.1029/2022WR033195 

This resource contains example model input and output data for Olorunsaye and Heiss (2024). Olorunsaye, O., & Heiss, J. W. (2024). Stability of saltwater‐freshwater mixing zones in beach aquifers with geologic heterogeneity. Water Resources Research, e2023WR036394, 1–22. https://doi.org/10.1029/2023WR036056 

The interactions between the atmosphere, ocean, and beach in the swash zone are dynamic, influencing water flux and solute exchange across the land-sea interface. However, the integrated role of these interactions in governing transport processes within the swash zone remains unexplored. This study employs groundwater simulations to examine the combined effects of waves and evaporation on subsurface flow and salinity dynamics in a shallow beach environment. Our simulations reveal that wave motion generates a saline plume beneath the swash zone, where evaporation induces hypersalinity near the sand surface. This leads to the formation of a hypersaline plume beneath the swash zone during periods of wave recession, which extends vertically downward, driven by the resulting vertical density gradients. This hypersaline plume moves landward and down the beachface due to wave-induced seawater infiltration and is subsequently diluted by the surrounding saline groundwater. Furthermore, swash motion increases near-surface moisture, leading to an elevated evaporation rate, with dynamic fluctuations in both moisture and evaporation rate due to high-frequency surface inundation caused by individual waves. Notably, the highest evaporation rates on the swash zone surface do not always correspond to the greatest elevations of salt concentration within the swash zone. This is because optimal moisture is also required – neither too low to impede evaporation nor too high to dilute accumulated salt near the surface. These insights are crucial for enhancing our understanding of coastal groundwater flow, biogeochemical conditions, and the subsequent nutrient cycling and contaminant transport in coastal zones. 

This archive contains field data used to investigate swash velocities by Britt Raubenheimer, Steve Elgar, and Alexandra Muscalus. The quality controlled cross-shore velocity time series are in the .zip folder "u", and the quality-controlled alongshore velocity time series are in the .zip folder "v". Details about the files and data are provided in README.txt. For further questions, please contact Britt Raubenheimer at braubenheimer@whoi.edu, Steve Elgar at elgar@whoi.edu, or Alexandra Muscalus at alexandra.muscalus@whoi.edu Support was provided by the National Science Foundation, the US Coastal Research Program, and the WHOI Build the Base Program. 

This resource includes the data from the Journal of Hydrology manuscript Hydraulic head fluctuations in an intermediate depth aquifer. The data set includes the 3-year time series of hydraulic heads presented in the manuscript as well as the .hds files from the MODFLOW-NWT runs. 

Alongshore array of ADVs in 2-m water depth and one ADV in inner surfzone