Small island communities worldwide face a water crisis decades in the making, as the legacy of inadequate planning and unsustainable extraction has accelerated saltwater intrusion (SWI), threatening their most vital resource. Existing research often lacks integrated long-term hydrologic datasets needed to link climate variability, groundwater use, and SWI in volcanic island aquifers. As climate pressures intensify, advanced modeling is essential for course-correction and long-term resilience. To address this limitation, this study leverages multi-decadal hydrologic data (1984-2025) to develop and parameterize a density-dependent numerical groundwater model for assessing SWI dynamics in Tutuila, American Samoa. Streamflow, groundwater levels, pumping rates, and chloride concentrations are compiled and analyzed to characterize long-term hydrologic drivers of SWI. Processed datasets inform the development and parameterization of a three-dimensional, variable-density FEFLOW model of coastal groundwater flow and solute transport in Tutuila. Preliminary results reveal strong spatial and temporal trends in groundwater levels and SWI driven by geologic heterogeneity, episodic recharge, and localized pumping intensity rather than uniform, long-term trends. Results highlight strong sensitivity of saltwater intrusion to episodic recharge variability, with drought periods producing amplified salinity responses across low-elevation coastal aquifers. Gaps in long-term hydrologic data constrain understanding of saltwater intrusion processes; however, data-driven modeling approaches enable evaluation of key drivers and management alternatives. This work demonstrates how cutting-edge modeling can guide small island communities toward water security as climate-related risks compound and traditional management approaches lose their viability.