Author(s): Elena Sanchez-Badorrey; Beatriz Sierra-Ruiz; Juan Flores-Gallardo

Linked Author(s): ELENA SANCHEZ-BADORREY

Keywords: submarine groundwater discharge, barrier island urbanization, climate change, fisheries, water quality

Abstract: Coastal barriers separating open sea of partially isolated inland or transitional water masses like coastal lagoons, ponds or lakes are worldwide present. Often enriched by nutrients and other bioactive solutes, submarine groundwater discharge (SGD) from coastal barriers plays an important role on the water quality of nearshore environments. Thus, affecting the biological productivity and sustainability of nearby fisheries. Hydraulic gradients and aquifer permeability govern the SGD dynamics across sand barriers. The increasing frequency of extreme events is expected to significantly affect present SGD fluxes and mass balance between sand barriers and coastal waters. Thus, open sea level variations on short and seasonal time scales are being amplified by barotropic and wind-drag tides induced by storm events. This effect enhances the hydraulic gradient dynamics, affecting the SGD fluxes. However, the presence of deep foundations in urbanized coastal barriers can modify the effective permeability of the aquifer. Hence, the impact of climate change on SGD fluxes might be different in urbanized and non-urbanized sand barriers. In this contribution, we illustrate this effect by modelling the SGD fluxes across the Beach Point barrier (Cape Cod, EEUU, North Atlantic coast) under severe storm conditions. The Beach Point numerical model (MODFLOW) was first validated using field data and climate data in the site during April 2007. The impact of deep foundations on the daily averaged SGD and the cumulated water volume exchange (V) across the barrier is investigated. Model results confirm the significant impact of deep foundations on the SGD and mass fluxes across the barrier, if compared with the non-urbanized case. Moreover, the daily averaged seaward SGD is found to be increased or reduced depending on the depth, number, typology and location of the deep foundations. This opens up the possibility of designing deep structures for controlling mass exchange across barrier islands. Finally, we analyze practical implications of these results for the productivity and sustainability of fisheries in the proximity of sand barriers.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022SS1514

Year: 2022