The goal of this dissertation is to contribute toward a better understanding of the flow and transport dynamics in saturated and unsaturated soils. In the first phase of this study, we have focused on understanding the impacts of climate change driven hydrological processes such as excess rainfall and/or draught cycles on saltwater intrusion processes with a focus on managing freshwater resources in island aquifers. As part of this effort, we used a combination of laboratory experiments and numerical simulations to study the impacts of changes in rainfall patterns on saltwater intrusion dynamics. In the second phase of this study, we have focused on understanding soil moisture storage processes in unsaturated soils. The knowledge of water stored in unsaturated soil is indispensable for several hydrological and geoenvironmental processes. The accuracy of the soil moisture transport models used in these studies depends on the precise characterization of saturated and unsaturated soil properties. In this effort, we developed novel experimental methods and modeling tools for developing soil characteristic models such as the van Genuchten and Brooks and Corey models using measured soil moisture and capillary pressure data. Also, in recent years, there has been increasing interest in developing remote sensing tools to measure soil moisture at multiple scales. As part of this research, to benchmark a novel radar technology, we collaborated with the remote sensing center to develop in-situ soil moisture datasets at a test facility in fine spatiotemporal scales.