22-10 Impact of Dynamic Shoreline Migration on Coastal Aquifer Response to Sea Level Rise

Session: Advances in characterizing groundwater, surface water, and their interactions (Posters)

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Abstract:

Coastal aquifers are classified as either recharge-limited or topography-limited based on how they respond to sea level rise (SLR). In recharge-limited systems, unsaturated accommodation space allows the water table to rise with SLR, maintaining constant fresh aquifer volume. In contrast, topography-limited systems restrict water table rise, leading to decreased fresh aquifer volume following SLR.

Previous models establishing this framework assume a static "armored" shoreline that remains fixed during SLR. However, in natural systems, the shoreline migrates landward with rising sea level, changing the aquifer length, recharge area, and freshwater-saltwater interface tip location—all factors that affect fresh aquifer volume.

This study systematically characterizes how dynamic shoreline migration affects both topography- and recharge-limited coastal aquifers under SLR. We constructed coupled groundwater flow and transport models in MODFLOW 6 using the buoyancy package with time-varying ocean boundary conditions to represent a range of coastal aquifer configurations. By comparing static versus dynamic shoreline scenarios across varying SLR rates and topographic slopes, we demonstrate the impact of lateral shoreline migration on coastal aquifer models. Our results show that fresh aquifer volume decreases in both recharge- and topography-limited systems when shoreline migration is included, though topography-limited systems remain more vulnerable to SLR.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2, 2026

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