Experimental Study of Seawater Intrusion in Stratified Layers with Sloping Ocean–Aquifer Boundary

Seawater intrusion (SWI) is a concern for coastline-saturated aquifers because it increases salinity, which contaminates and degrades groundwater quality. Rising sea levels and other natural processes, as well as anthropogenic activities such as overpumping, are the causes of intrusion. Because these experiments are the most reliable methods for study, this study focused on the experimental investigation of SWI in a hypothetical stratified aquifer with parallel and perpendicular stratification and a sloping beach boundary. Stratified media were formed by stacking layers in parallel and perpendicular layers in different combinations. Sensitivity analysis was performed with 10-, 20-, and 30-cm gaps for interactions with 4-layer formations with height to toe length expanding from 0.12 to 2.33. High-resolution images were captured at specified intervals and demarcated for a clear visualization of intrusion. A homogenous base case was used to evaluate the feasibility of the proposed method and the results were compared with those of a sandbox apparatus and found to be consistent in terms of the shape of the wedge and the toe length. The height of the intrusion ranges from 28.3 to 32.2 cm. The intrusion was fast and accurate due to the higher permeability of the material. It was concluded that the toe length–height ratio varies from 0.43 to 7.0. For materials with lower permeabilities, this ratio is small because the intrusion is slow but steady in both directions; however, for materials with higher permeabilities, this ratio corresponds to a higher value. The intrusion is restricted to the individual layer until it encounters an impervious layer and follows a proportional pattern with an increasing area of intrusion as the opening area increases.