Date of Award
2026
Degree Type
Dissertation
Degree Name
Doctor of Philosophy in Biological and Environmental Sciences
Department
Biological Sciences
First Advisor
Soni Pradhanang
Abstract
Coastal aquifers supply freshwater to nearly half of the world’s coastal population, yet they are increasingly threatened by sea-level rise (SLR), climate-driven shifts in precipitation, and growing anthropogenic pressures. This dissertation advances the scientific understanding of coastal groundwater vulnerability by integrating global-scale synthesis, numerical modeling, Geospatial analysis, and climate-driven risk assessment to evaluate the resilience of coastal aquifers, with a focus on southern Rhode Island, USA.
First, a global systematic review of publications (1953-2023) was conducted to assess the evolution of modeling approaches used to investigate freshwater-saltwater interactions in coastal aquifers. The review highlights major advances in numerical modeling (e.g., SEAWAT, SUTRA, FEFLOW), the growing use of geophysical tools (ERT, VES, GPR), and persistent challenges related to data scarcity, heterogeneity, and model uncertainty. The synthesis identifies critical research gaps, including limited integration of field-based geophysics with density-dependent flow models and insufficient regional assessments in data-poor coastal zones.
Building on these insights, a three-dimensional transient groundwater flow model (MODFLOW-NWT) was developed for the Ninigret Frontal Block Island Sound (NFBIS) watershed in southern Rhode Island to quantify the impacts of projected SLR and altered precipitation through 2075. Nine climate scenarios combining historical, intermediate, and extreme projections show that groundwater levels will rise across the watershed, with the most substantial increases occurring under high-SLR and extreme-precipitation conditions. Results indicate up to a 7% expansion of groundwater inundated areas, widespread reduction in depth to groundwater, and a shift in groundwater discharge pathways --decreasing coastal groundwater discharge while increasing terrestrial discharge to streams and wetlands. These changes elevate risks to freshwater resources, coastal ecosystems, and subsurface infrastructure.
Finally, groundwater numerical model was coupled with GIS to develop vulnerability maps to evaluate the exposure of onsite wastewater treatment systems (OWTS), roads, and residential basements to rising groundwater. By 2075, areas classified as “very high vulnerability” increase by ~58% for OWTS, >250% for roadways, and expand substantially for residential basements, indicating chronic seepage, structural instability, and reduced wastewater treatment performance. The results demonstrate that groundwater rise - often occurring before surface flooding - poses a hidden but critical hazard to coastal communities.
Collectively, this dissertation provides a comprehensive, multi-scale evaluation of coastal aquifer vulnerability under climate change. It advances methodological integration across numerical modeling, and spatial risk assessment, and delivers actionable insights for groundwater management, infrastructure planning, and climate adaptation in Rhode Island and other shallow, glacially derived coastal aquifers worldwide.
Recommended Citation
Ismail, Mamoon, "ASSESSMENT OF WATER RESOURCES IN COASTAL AQUIFER IN SOUTHERN RHODE ISLAND USING NUMERICAL SIMULATIONS" (2026). Open Access Dissertations. Paper 4573.
https://digitalcommons.uri.edu/oa_diss/4573