New Analysis Finds Rising Seas Could Threaten as Many as 392 of California’s Critical Infrastructure Assets

WASHINGTON—Climate change is rapidly worsening tidal flooding and escalating risks to essential and valuable coastal infrastructure that millions of people depend on. According to a new analysis released today by the Union of Concerned Scientists (UCS) titled “Looming Deadlines for Coastal Resilience,” nearly 1,100 critical infrastructure assets along the U.S. coastline would flood 12 times per year on average, or the equivalent of once a month, by 2050, assuming a medium rate of sea level rise. That number could jump to more than 5,300 critical infrastructure assets at risk by 2100. The more than 1,700 U.S. communities with at-risk critical infrastructure assets between now and the century’s end are currently home to nearly 7.4 million people, with California’s communities and infrastructure highly exposed. As tidal flooding risks to expensive, long-lived infrastructure grows rapidly in the decades ahead, policymakers and decision makers from every sector of society must take urgent actions to prepare communities and sharply curtail the use of fossil fuels driving the climate crisis.

The results for California are quite sobering. Assuming a medium sea level rise scenario (3.2 feet globally, on average, by 2100) and bearing in mind that the amount of sea level rise experienced along U.S. coastlines by century’s end is less certain as it is largely dependent on heat-trapping emissions released in the coming decades:

• As many as 137 of today’s critical infrastructure assets would be at risk of being flooded, on average, twice annually by 2050. Of those assets, 118 would be at risk of flooding the equivalent of once each month and 110 the equivalent of once every other week.
• By the end of the century, as many as 392 of today’s critical infrastructure assets would be at risk of flooding, on average, twice annually by 2100. Of those assets, 311 would be at risk of flooding the equivalent of once each month and 280 the equivalent of once every other week.
• California ranks fifth in 2050 and 2100 for infrastructure at risk of disruptive flooding.
• The critical infrastructure most at risk of disruptive flooding includes industrial contamination sites, energy infrastructure, and public health and safety buildings in 2050 and 2100.
• In 2050, there are 48 communities with at-risk critical infrastructure. By 2100, it jumps to 136 communities.
• The number of critical infrastructure assets at risk of disruptive flooding is expected to increase 19% by 2050 and triple by 2100, as compared to a 2020 baseline.

To view the national press release with quotes from the report authors, click here.

Using a combination of data from National Oceanic and Atmospheric Administration (NOAA) tide gauges, U.S. government agencies, and three sea level rise scenarios developed by a U.S. Interagency Task Force—referred to as high, medium, and low in the report—UCS determined when critical infrastructure assets along the entire coastline of the contiguous United States, as well as Guam, Puerto Rico and the U.S. Virgin Islands, would be at risk of being routinely flooded by high tides at least two, 12 or 26 times per year, on average, in the coming decades. Critical infrastructure is defined in the analysis as assets and facilities that provide functions necessary to sustain daily life or that if flooded could impose societal hazards. The analysis includes results for 2020, 2030, 2050 and 2100 for six types of critical infrastructure: educational institutions, energy infrastructure, government facilities, industrial contamination sites, public health and safety buildings, and subsidized housing. It also utilizes the White House Council on Environmental Quality’s Climate and Economic Justice Screening Tool to ascertain if the infrastructure at risk of flooding is located in “disadvantaged” or “non-disadvantaged” communities, as defined by the tool. Factors that contribute to a community being considered disadvantaged include burdens they face related to health, housing, climate change and income. This analysis only considers present-day infrastructure and population data, which means the results may be conservative. More information about the methodology used in this report can be found here.

Due to a variety of factors—coastline length, sea level rise rate, land subsidence and zoning laws—some states have more critical infrastructure assets exposed to disruptive tidal flooding in the coming decades than others. The analysis finds that California, Florida, Louisiana, Maryland, Massachusetts, and New Jersey have the highest numbers of critical infrastructure assets that will need to be made more resilient or be relocated to safer ground. Meanwhile, because of longstanding racial and socioeconomic inequities, disadvantaged communities that already carry heavy burdens have, on average, more infrastructure at risk of flooding and fewer resources to address this challenge. According to the analysis, about one-third of coastal communities are currently designated as disadvantaged, but they are home to more than half of the critical infrastructure at risk through 2050. Disadvantaged communities with infrastructure at risk have higher percentages of Black, Hispanic or Latino, and Native American residents and more infrastructure at risk per capita than non-disadvantaged communities. Public and affordable housing represents the single most at-risk category of vital infrastructure.

The report offers a range of recommendations for policymakers and public and private decision makers to ensure communities are adequately prepared for the risks and challenges that lie ahead. The recommendations include using the best available science to inform near- and long-term risk planning and scaling up public and private funding—beyond allocations in existing policies such as the Infrastructure Investment and Jobs Act—to increase the climate resilience of coastal infrastructure. The report also encourages implementing policies to reduce historical inequities and prevent future harms, protecting subsidized housing when possible, opening just opportunities for people or communities that opt to relocate, and planning for a wide range of possibilities that could occur as sea level rise rapidly accelerates.

Even if all global heat-trapping emissions ceased today, much of the expected sea-level rise between now and midcentury is already locked in due to insufficient efforts to reduce emissions by policymakers to date, and the obstructive and damaging actions of fossil fuel companies. However, the amount of sea level rise that occurs between 2050 and 2100 depends on global heat-trapping gases released over the next several decades and Earth’s physical response—namely the extent of land-based ice loss and ocean warming—caused by those emissions. This is why sharply curtailing heat-trapping emissions, phasing out fossil fuels and ramping up clean energy solutions must also be cornerstones of actions to help protect coastal communities.

To view the report PDF, click here.

Spreadsheets with UCS data on the infrastructure at risk in specific states and communities are available for the following timeframes: 2020, 2030, 2050 and 2100.

To use the interactive mapping tool, click here. The map allows you to learn more about the infrastructure at risk in specific communities or states. When you zoom in, the maps become more detailed.

For all other materials, including state press releases, report methodology, case studies, and Spanish-language materials, click here.