By Patricia Ramalho de Barros Leite and Alison N. Schulenburg et.al
Drivers of Saltwater Intrusion
Sea level rise (SLR) poses a significant threat to coastal regions. Along the Eastern Seaboard of the United States, coastal agricultural fields are particularly vulnerable. As sea levels continue to rise along the coasts, saltwater can encroach into uplands, a phenomenon known as saltwater intrusion (SWI) (Tully et al., 2019).
SWI occurs when seawater floods low-lying areas or infiltrates freshwater systems, raising groundwater levels and salinity. Prolonged droughts exacerbate this impact by depleting freshwater availability and increasing evaporation, which in turn further concentrates salts in the soil.
There are two primary pathways by which SWI affects coastal farmlands:
Bottom-up intrusion
This process occurs when elevated groundwater levels or pressure from nearby saline bodies gradually force saltwater into lower soil horizons. This process alters soil chemistry, damages root systems, and reduces soil fertility. Consequently, bottom-up SWI can be particularly insidious because it occurs below the soil surface, posing distinct challenges for agricultural management and making it difficult to detect and remediate (de Barros et al., 2025).
Top-down intrusion
Top-down saltwater intrusion is caused by tidal flooding, storm surges, or overtopping of saline ditches, which deposit salt directly onto the soil surface. Though more visible, this process can be intermittent, depending on the frequency of flooding events.
Source : umd.edu