Inclined Physical Subsurface Barriers for Saltwater Intrusion Management in Coastal Aquifers

Saltwater intrusion (SWI) has a negative environmental impact on groundwater quality in coastal areas. Therefore, effective management strategies are required to preserve fresh groundwater resources. Historically, vertical barriers have been exclusively considered in both numerical studies and practical applications. The novelty of this study consists in investigating the SWI mitigation effectiveness of inclined physical subsurface barriers (PSBs), and specifically cutoff walls (CWs) and subsurface dams (SDs). An initial benchmark analysis of the Henry problem was performed. Following verification, the proposed model was applied to a real case study - the Biscayne aquifer (Southeastern Florida, USA). The model simulations run for different scenarios considering the vertical placement of the PSB, an inclined placement of the PSB according to different slopes (1/4, 1/2 and 1/1, at sea- and landside) and the combination of the best scenario. The results showed that CWs are more effective in limiting SWI in comparison with SDs. The most positive impact in both cases was achieved for a slope of 1/4, indicating that a moderate vertical inclination of the PSB better preserve coastal groundwater resources. The model presented in this work can be a valuable tool for policy makers in predicting the coastal aquifer response. However, a comprehensive cost-benefit analysis is required to further account for the feasibility and the economic costs related to the construction of inclined PSBs.