Thousands of hazardous facilities along U.S. coastlines sit in the path of rising seas, intensifying storms, and seismic threats that could release toxic contamination into surrounding communities. A growing body of peer-reviewed research now quantifies the scale of that exposure, and the numbers are sobering: more than 5,500 sites, from sewage treatment plants to refineries, face significant flood risk by the end of this century under a high emissions scenario. The convergence of climate-driven sea level rise, earthquake-induced land subsidence, and eroding natural barriers is creating overlapping hazards that federal oversight has been slow to address.
Toxic Sites Facing Flood Risk by 2100
A national assessment published in Nature Communications analyzed more than 47,600 coastal hazardous facilities across the United States, including refineries, fossil fuel terminals, and sewage treatment operations. Under a high emissions scenario, more than 11% of those facilities, roughly 5,500 sites, are projected to face flooding at a 1-in-100-year frequency or greater by 2100. That projection means the facilities most likely to leak heavy metals, petroleum products, or industrial chemicals into floodwaters are also the ones most exposed to inundation as oceans rise and storms grow more severe.
UCLA Fielding School of Public Health researchers led the study and found that many of these at-risk sites sit in or near marginalized communities, compounding the public health consequences of any toxic release. Separately, the EPA’s Office of Inspector General concluded that 49 of 157 federal facility Superfund sites on the National Priorities List are potentially at risk from sea-level rise or increased storm surge. The Inspector General’s findings raise pointed questions about whether existing cleanup remedies at those sites will hold up as coastal conditions worsen. If containment systems designed for a stable shoreline fail under repeated flooding, contaminated groundwater and sediment could migrate well beyond current site boundaries.
Earthquake Subsidence Compounds Rising Seas
Sea level rise alone does not capture the full danger. In the Pacific Northwest, researchers have modeled what happens when a major earthquake strikes a coast already contending with higher water. A peer-reviewed paper in the Proceedings of the National Academy of Sciences, supported by the USGS Earthquake Hazards Program, found that a future magnitude 8 or greater Cascadia subduction zone earthquake could cause sudden coastal subsidence of up to about 2 meters. That drop in land elevation would dramatically expand 1-in-100-year floodplains across 24 estuaries in the region, according to the study available via PubMed Central, placing additional wastewater plants, fuel depots, and chemical storage yards within reach of storm surge and tsunami waves.
The practical consequence is that homes, roads, and infrastructure currently considered safe from flooding could be submerged in minutes, not decades, with little time to secure hazardous materials or shut down vulnerable processes. Reporting in national outlets has translated these findings into public-risk terms, drawing comparisons to the 2011 Japan earthquake and the 2004 Sumatra disaster, both of which involved rapid coastal land changes that overwhelmed existing defenses. When earthquake-driven subsidence is layered on top of climate-driven sea level rise, the resulting flood exposure exceeds what either hazard would produce in isolation. For communities near hazardous facilities, this compound scenario means contamination risk could spike without warning during a seismic event, long before gradual sea level rise triggers planned adaptation measures.
Historic Landfills and Eroding Natural Defenses
The threat extends beyond active industrial sites. A peer-reviewed synthesis in WIREs Water established that historic landfills in low-lying coasts and estuaries are uniquely vulnerable because they are unlined, have poor records of what was buried, and sit exposed to flooding and erosion. Many of these dumps were sealed decades ago under regulations that did not anticipate significant shoreline change, so they lack engineered caps, leachate controls, or seawalls sized for future sea levels. A separate method paper in Anthropocene Coasts describes a screening and ranking tool designed to prioritize historic coastal landfills by pollution risk, offering regulators a way to identify which sites need urgent attention before they erode into open water.
Natural coastal barriers that once slowed erosion are themselves disappearing, leaving these forgotten dumps more exposed each year. Research on urban shorelines in Vietnam documents how the loss of mangrove forests and coral reefs amplifies the destructive power of typhoons and storm surges, a pattern echoed in many tropical and subtropical deltas. An estimated 30% to 50% of coral reefs globally have already been lost over the past few decades, and some scientists warn that another strong El Niño could trigger widespread reef collapse, further weakening natural breakwaters. Parts of the Great Barrier Reef’s outer reefs still function as a buffer against coastal recession, but that protective capacity is shrinking as ocean temperatures climb. Without these biological defenses, wave energy reaches shorelines with greater force, accelerating erosion of the very land where many hazardous sites and historic landfills were built.
Federal Oversight Gaps and Aging Maritime Risks
One common assumption in current coverage is that existing federal programs, primarily Superfund and EPA enforcement, are equipped to handle the intersection of climate change and toxic site management. The evidence suggests otherwise. The EPA’s own climate indicators show that the frequency of coastal flooding has increased since the 1950s and has accelerated in recent decades, while NOAA projections anticipate about a foot of additional sea level rise along U.S. coastlines by mid-century. Yet the Inspector General’s review of federal facility cleanups indicates that many remedies were designed for historical water levels and storm patterns, with limited consideration of compound hazards such as subsidence, groundwater rise, or back-to-back extreme events. In practice, that means caps, slurry walls, and pump-and-treat systems could be overtopped or undermined far sooner than their intended design life, especially where budgets for long-term monitoring remain tight.
These gaps extend offshore, where aging tankers and storage vessels add another layer of risk to coastal waters already stressed by climate change. An investigation by The Guardian into Iran’s so‑called shadow fleet describes how older, poorly regulated oil tankers have proliferated in recent years, often operating under flags of convenience and outside normal safety regimes. While that reporting focuses on geopolitical sanctions, the environmental implications are clear: a major spill from a structurally compromised vessel could foul hundreds of miles of coastline, infiltrate estuaries that already host hazardous facilities, and turn a chronic risk landscape into an acute disaster. In such a scenario, emergency responders would be forced to manage overlapping plumes of petroleum, industrial chemicals, and landfill leachate, stretching cleanup capacity and complicating decisions about which communities and ecosystems to protect first.
Planning for Compound Coastal Disasters
Researchers and public health experts argue that preparing for this future requires a shift from single-hazard planning to a compound-risk framework that explicitly integrates climate, seismic, and ecological dynamics. That means mapping not just where floodwaters will reach, but how contaminants could move through groundwater, sediments, and food webs once barriers fail. It also means using tools emerging from coastal science and environmental engineering to prioritize the most dangerous sites for early action, whether through relocation of hazardous materials, construction of adaptive barriers, or, where feasible, managed retreat from the most vulnerable zones. Databases curated by institutions such as the National Center for Biotechnology Information can help local officials and health departments understand the toxicological profiles of substances stored at coastal facilities, improving risk communication and medical preparedness when storms or earthquakes strike.
Ultimately, the science now available leaves little doubt that thousands of hazardous coastal sites sit on the front lines of climate and seismic change, even if regulatory frameworks have yet to fully catch up. The studies on flood exposure, subsidence, landfill erosion, and ecosystem loss collectively point to a narrow window for preventive action before incremental sea level rise and sudden tectonic shifts begin to overwhelm existing defenses. Whether federal and state agencies move quickly to update design standards, enforce stronger oversight of both onshore facilities and offshore shipping, and invest in nature-based protections will determine whether future storms and earthquakes merely test the system—or trigger cascading contamination events that transform vulnerable coastlines into long-term sacrifice zones.
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*This article was researched with the help of AI, with human editors creating the final content.
