Coastal Groundwater Inundation Group: Facing Puerto Rico’s Hidden Coastal Threat

In October 2018, the Coastal Groundwater Inundation Group was conceived and coordinated by Pedro González of MARESociety. This multidisciplinary team brought together experts and community leaders determined to confront an invisible but growing coastal hazard in Puerto Rico.

The group included:

• Two hydrogeologists from the U.S. Geological Survey

• A physical oceanographer from the University of Puerto Rico’s Marine Science Department

• The Coastal Manager and Director of the Sea Grant College at UPR–Mayagüez

• Two independent engineer-hydrologists

• Several community leaders

Together, they set out to study a phenomenon few had considered: groundwater inundation caused by rising seas.

The Unseen Hazard Beneath Our Feet

While most discussions of sea level rise focus on visible flooding, this group addressed a less obvious but equally dangerous threat: groundwater inundation.

Even during dry periods, in certain low-lying coastal areas, seawater can push inland underground. The result? Saltwater rises into elevator shafts, underground parking lots, residential courtyards, and stormwater drainage systems causing damage long before waves or rain arrive.

This phenomenon is most evident during spring tides, ocean swells, strong onshore winds, and heat waves. It compromises the foundations of roads, the structural integrity of buildings, and the effectiveness of drainage infrastructure, leaving communities more vulnerable to rain-induced flooding and water stagnation.

The Cost of Inaction

The group emphasized a difficult truth: mitigation will be costly, but inaction will be catastrophic.

Adapting to groundwater inundation requires long-term planning, financing, and construction. And yet, as sea level rise accelerates exponentially, waiting only increases the risks. The problem is compounded by scientific uncertainty—multiple interacting factors influence sea level rise, making projections complex.

Still, one fact is clear: groundwater inundation is already happening, and proactive action is essential.

Monitoring, Modeling, and Mitigation

To confront this challenge, the group highlighted the urgent need for:

• Specialized monitoring instruments to track groundwater levels

• Hydrogeological and oceanographic studies to understand processes

• Mathematical modeling to project future inundation and identify mitigation measures

With better data, Puerto Rico can prepare strategies to reduce risks, protect infrastructure, and safeguard socio-economic stability in coastal communities.

From Science to Policy

Recognizing the importance of connecting science with decision-making, the problem was presented to Hon. Henry Neuman, Puerto Rico Commonwealth Senator, who expressed concern and support for the project.

This collaboration between scientists, engineers, community leaders, and policymakers underscores the campaign’s mission: to shine a light on a hidden threat and ensure that Puerto Rico is prepared for the challenges of tomorrow.

Takeaway: Coastal risks are not limited to what we see on the surface. Beneath our feet, rising seas are quietly reshaping the future of our coasts. Addressing groundwater inundation today is critical to protecting Puerto Rico’s communities and infrastructure tomorrow.