Beach groundwater dynamics play a critical role in coastal ecosystem functions, particularly in low-lying beach habitats used for nesting by endangered species like sea turtles. Incubating nests are susceptible to prolonged inundation below the groundwater table (GWT), as flooding duration critically affects egg viability. Understanding how oceanic processes and rain drive GWT fluctuations in the nesting area is essential for evaluating nest relocation strategies and designing nature-based solutions that mitigate nest flooding. Here, we analyze how infragravity waves, tides, storm surge, and rainfall drive short-term fluctuations (hourly to weekly) in the beach GWT on Galveston Island, Texas—a dissipative, mild-sloping barrier island system along the northwestern Gulf of Mexico coast. Applying tailored spectral analyses to field observations collected in 2023, we show that surge and rainfall dominate short-term GWT response in the nesting area, while higher-frequency wave and tidal signals are increasingly damped landward. To facilitate this analysis, we classify observed water levels into groundwater, mixed, and submerged regimes based on estimated wave runup. A flooding threshold analysis reveals multiple, prolonged nest inundation events (exceeding 12 h) across the backshore, even for the shallowest nests. This strongly suggests that Galveston Island’s beaches are currently unsuitable for turtle nesting, underscoring the need to continue the ongoing nest relocation program and further research nature-based solutions that enable sea turtle nesting (e.g., turtle-friendly nourishments).

Beach groundwater and nearshore hydrodynamic data were collected during a field experiment along two dissipative beach transects on Galveston Island, Texas, in the fall of 2023. The monitored beaches serve as nesting habitat for the critically endangered Kemp’s ridley sea turtle. Conditions ranged from calm to stormy, with two storms occurring during the experiment, inundating the entire beach up to the dune toe. Collected hydrodynamic data include readings from pressure loggers submerged in the foreshore and mounted in groundwater wells in the backshore, data from two wave buoys about 1.5 km offshore, and GoPro timestacks of the instantaneous waterline (wave runup). Other collected data include bathymetry and topography surveys, subsurface temperature and moisture content readings, and sediment characteristics. This comprehensive dataset can be used to (1) study relevant beach inundation and groundwater processes, including their effect on the local ecosystem (e.g., repeated flooding of sea turtle nests), (2) study the propagation of nearshore hydrodynamic processes into the beach matrix and groundwater table, and (3) validate existing beach groundwater models.