Climate change is reshaping coastlines around the world, and sea level rise is one of its most tangible and consequential impacts. For geotechnical engineers, the stakes are high: the very ground beneath coastal infrastructure is changing—becoming softer, more saturated, and less predictable. Understanding how climate-induced sea level rise alters soil behavior, groundwater dynamics, and erosion patterns is no longer optional; it is essential for designing resilient foundations, protecting coastal communities, and managing long-term risk. This article explores the mechanisms of sea level rise, its direct effects on geotechnical investigations, and the adaptive strategies engineers must adopt to keep infrastructure safe and functional in a warming world.

What Is Sea Level Rise?

Sea level rise refers to the increase in the average height of the world’s oceans over time. The primary drivers are two: thermal expansion of seawater as it warms, and the addition of freshwater from melting ice sheets and glaciers. Over the past century, global mean sea level has risen approximately 15–20 centimeters (6–8 inches), but the rate has accelerated in recent decades—from about 1.4 mm per year in the early 20th century to roughly 3.6 mm per year since 2006, according to the Intergovernmental Panel on Climate Change (IPCC). Under high-emissions scenarios, the IPCC projects a rise of up to 1.1 meters by 2100, with some studies suggesting even higher values when ice-sheet instability is considered.

Regional variations are significant. Along the East and Gulf Coasts of the United States, relative sea level rise is amplified by land subsidence from groundwater extraction and sediment compaction. In Southeast Asia, mega-deltas like the Mekong and Ganges-Brahmaputra experience rates 2–3 times the global average. These local factors mean that geotechnical engineers must work with site-specific projections rather than global averages. Reliable data sources include NOAA’s sea level trends and the NASA Sea Level Change Portal, which provide high-resolution regional datasets.

Impacts on Coastal Geotechnical Investigations

Coastal geotechnical investigations—borings, cone penetration tests (CPT), soil sampling, and laboratory testing—are the foundation of safe design. Rising sea levels alter every phase of these investigations, from preliminary site characterization to final foundation recommendations. Below we examine the key physical mechanisms and their practical consequences.

Altered Soil Properties and Strength

One of the most direct effects of sea level rise is increased soil saturation. As water tables rise and flood events become more frequent, previously unsaturated soils become fully saturated. This reduces effective stress—the intergranular contact pressure that gives soil its strength—leading to lower bearing capacity and higher compressibility. For example, sands and silts that might have been dense and stable can become loose and collapsible. Clays may soften, reducing undrained shear strength.

Saltwater intrusion also plays a role. When fresh groundwater is replaced by saline water, the electrochemical environment changes, potentially causing clay flocculation or dispersion. These changes can alter plasticity indices and consolidation behavior, making laboratory results from historical sites unreliable for future conditions.

Increased Liquefaction Susceptibility

Liquefaction occurs when loose, saturated cohesionless soils lose their shear strength under cyclic loading—most commonly from earthquakes. Rising sea levels exacerbate this risk in two ways. First, a shallower water table means that once-dry sands are now saturated, expanding the zone of liquefiable material. Second, higher water pressures from more frequent storm surges can lead to post-cyclic strength loss even without seismic events. Geotechnical investigations must now include liquefaction hazard assessments that account for future water table elevations, not just present ones.

Coastal Erosion and Sediment Transport

Sea level rise accelerates shoreline erosion by raising the base level for wave attack. For geotechnical investigations, this means that site conditions are not static; erosion can remove overburden, expose buried strata, and undercut existing foundations. In many cases, the soil profile encountered during a boring today may be different from what exists even a few years later. Engineers must incorporate erosion projections into their site characterization, often using numerical models like USGS’s coastal change hazard models. Long-term monitoring of platform elevations and bathymetry is becoming a standard complement to traditional borings.

Flooding and Groundwater Rise

Higher base water levels increase the frequency and depth of flooding, both from storm surges and high tides (“sunny day flooding”). For geotechnical investigations, this creates challenges in accessing sites, keeping boreholes dry, and sampling undisturbed soils. Shallow groundwater can also lead to uplift forces on basement structures, cause swelling in expansive clays, and accelerate the corrosion of buried steel piles and sheet piles. Groundwater monitoring must become a multi-year endeavor, not a one-time measurement, to capture seasonal and tidal variations under a changing climate.

Saltwater Intrusion and Chemical Attack

As sea levels rise, the saltwater–freshwater interface in coastal aquifers moves landward. For geotechnical investigations, this means that soils and groundwater chemistry are shifting. Chloride ions can attack concrete foundations, causing corrosion of rebar and spalling. Sulfates in seawater can react with cement to form expansive minerals that crack concrete. Geotechnical investigations should include chemical analyses of soil and water to assess the long-term durability of foundation materials, and specify sulfate-resistant cement or protective coatings where needed.

Adapting Geotechnical Practices

To meet these challenges, the geotechnical community is evolving both investigation methods and design philosophies. Adaptation is not optional—it is a matter of public safety and economic viability for coastal developments worth billions of dollars.

Incorporating Climate Projections into Site Assessments

Traditional geotechnical reports typically reference static groundwater levels and 100-year storm events based on historical records. This approach is no longer adequate. Engineers must use scenario-based projections from climate models, including intermediate and high-emissions pathways, to evaluate how water tables, erosion rates, and flood elevations will change over the design life of a structure—often 50 to 100 years. The NOAA Sea Level Rise Viewer and the IPCC’s AR6 regional projections are practical starting points. These projections should be integrated into probabilistic risk assessments rather than deterministic single-value estimates.

Advanced Modeling and Remote Sensing

Geotechnical investigations benefit from modern tools that capture spatial and temporal variability:

  • Ground Penetrating Radar (GPR) and electrical resistivity tomography can map saltwater intrusion and water table depth over large areas.
  • Seismic CPT and shear wave velocity profiling help assess liquefaction potential with higher resolution.
  • InSAR (Interferometric Synthetic Aperture Radar) from satellites can detect millimeter-scale ground subsidence that exacerbates relative sea level rise.
  • Numerical modeling of coupled hydromechanical processes—such as finite-element flow models that simulate groundwater rise and slope stability—is becoming a routine part of site characterization.

Design of Resilient Foundations

Foundations designed for future conditions differ from conventional ones. Key strategies include:

  • Elevating foundations above projected flood levels, using piles or deep mat slabs.
  • Using corrosion-resistant materials such as epoxy-coated rebar, stainless steel, or fiber-reinforced polymers for piles and anchors.
  • Incorporating drainage systems to control groundwater pressures around basements and excavations.
  • Designing for scour around bridge piers and coastal structures using riprap, sheet piling, or deep foundations below expected scour depths.
  • Soil improvement techniques such as deep soil mixing, vibro-compaction, or prefabricated vertical drains in areas predicted to experience increased saturation.

Long-Term Monitoring and Adaptive Management

Because sea level projections carry significant uncertainty, a “design-and-forget” approach is insufficient. Geotechnical projects increasingly include monitoring plans: piezometers to track water tables, inclinometers to measure slope movement, and settlement plates to detect consolidation. Data from these instruments can trigger adaptive responses—such as raising structures, adding ballast, or installing additional drainage—as conditions evolve. This approach aligns with the concept of “managed adaptive design” promoted by coastal engineers and resilience planners.

Regulatory and Planning Considerations

Geotechnical investigations do not exist in a vacuum. They feed into zoning, permitting, and insurance decisions that shape coastal development. As sea level rises, regulatory frameworks are tightening.

Building Codes and Setback Lines

Many coastal jurisdictions have updated building codes to require minimum foundation elevations above base flood elevations (BFE) plus freeboard. In the United States, FEMA’s flood maps are being revised to incorporate future sea level rise, and the International Building Code (IBC) now includes provisions for increased scour and hydrostatic uplift. Geotechnical engineers must ensure that soil bearing capacities and settlement estimates are calculated for the saturated conditions that will exist when flood levels are reached.

Insurance and Risk Disclosure

Flood insurance premiums through the National Flood Insurance Program (NFIP) are rising in many coastal areas as risk models improve. Lenders and developers increasingly require geotechnical reports that explicitly address climate hazards. Failure to do so can lead to disputes, regulatory penalties, or uninsurable properties. Some states, like California and New York, have laws requiring disclosure of flood risk—including groundwater rise—in real estate transactions.

Case Studies: Where the Impact Is Already Visible

Real-world examples illustrate the urgency of adapting geotechnical practice to sea level rise:

  • Miami Beach, Florida: The city has invested over $500 million in stormwater pumps, raised roads, and improved drainage to combat tidal flooding. Geotechnical investigations for new high-rises must now include deep pile foundations designed for a rising water table and saltwater corrosion. Soil conditions have shifted from relatively dry limestone to nearly fully saturated karst, requiring careful evaluation of sinkhole risk.
  • New Orleans, Louisiana: Post-Katrina levee improvements required extensive geotechnical investigations of soils that had been submerged and compacted under unusual hydraulic loading. The U.S. Army Corps of Engineers (USACE) used advanced CPT and lab testing to characterize remolded clays and sands. Future evaluations now account for relative sea level rise of up to 1 meter per century due to subsidence.
  • The Netherlands: As a global leader in coastal adaptation, Dutch engineers have long accounted for sea level rise in their geotechnical designs. The Maeslantkering storm surge barrier and Delta Works rely on deep foundations of piles and concrete caissons in constantly evolving seabeds. Their approach—monitoring, modeling, and adaptive engineering—is a template for other nations.

Future Directions in Geotechnical Investigation

Looking ahead, several trends will shape how geotechnical engineers address sea level rise:

  • AI and Machine Learning: Automated interpretation of CPT data, satellite imagery, and historical records can help identify areas most vulnerable to soil property changes under rising seas.
  • Real-time environmental sensing: Distributed networks of low-cost sensors (water level, temperature, pore pressure) will feed into digital twins of coastal sites, enabling continuous updating of geotechnical models.
  • Nature-based solutions: Living shorelines, such as oyster reefs and mangrove restoration, require geotechnical evaluation of substrate stability and root reinforcement—a growing sub-discipline.
  • Standardization of climate-integrated geotechnical reports: Professional organizations (ASCE, DFI, GEO) are developing guidelines for incorporating climate change into site investigations. Adoption will likely become mandatory in high-hazard coastal zones.

Conclusion

Climate-induced sea level rise is not a distant threat—it is already altering the physical properties of coastal soils, raising groundwater tables, accelerating erosion, and increasing the risk of liquefaction and flooding. Geotechnical investigations must evolve from static, single-point assessments to dynamic, multi-decade evaluations that incorporate climate projections, advanced modeling, and adaptive design. By embracing these changes, geotechnical engineers can help build coastal infrastructure that is not only safe today but resilient for the generations to come. The science is clear: rising seas are a geotechnical reality, and our practices must meet the moment.