Aging Defenses: As Atmospheric Rivers Intensify, America’s Levees Face a Critical Test
Record rainfall and increasingly powerful storms are pushing aging levee systems to their breaking point across the United States, threatening millions of people and trillions of dollars in property. Recent breaches in Washington state highlight a nationwide crisis of infrastructure vulnerability and unequal risk.
Brandon Bell/Getty Images
The relentless onslaught of atmospheric rivers across the West Coast in recent weeks has exposed a hidden vulnerability in America’s infrastructure: its aging levee systems. As rivers swelled beyond capacity, multiple levees – often overlooked barriers protecting communities from floodwaters – were overtopped or breached, inundating towns and forcing evacuations. This isn’t a regional problem; it’s a national one, exacerbated by a changing climate and decades of deferred maintenance.
From Humble Beginnings to Critical Infrastructure
Many assume today’s levees are the product of modern, meticulously engineered flood control plans. The reality is far more organic. The vast majority began as simple earthen embankments, constructed by farmers in the 19th and early 20th centuries to shield fields and livestock from seasonal overflows. These early structures were built on practical experience, not rigorous engineering standards.
Over time, the landscape transformed. Farmlands gave way to residential areas, transportation networks expanded into floodplains, and populations grew. What started as localized protection for agricultural land gradually became the first line of defense for millions of people and vital infrastructure. This evolution occurred largely without comprehensive planning or public debate, leaving many levees ill-prepared for the immense responsibility they now bear.
AP Photo/Manuel Valdes
A System Under Strain
Today, the U.S. Army Corps of Engineers’ National Levee Database lists over 24,000 miles of levees, averaging 61 years in age – and many are considerably older. These structures protect more than 23 million people, approximately 7 million buildings, and nearly $2 trillion in property value. This represents an extraordinary responsibility for a system often characterized by inconsistent maintenance and oversight.
While some levees undergo regular inspections, others are owned by small local agencies or even private entities with limited resources. In some cases, responsibility is fragmented or unclear. The recent breach along the Green River in Washington state, for example, was delayed due to disagreements between governing bodies, as reported by The Seattle Times, forcing thousands to evacuate.
National Weather Service Archival Photography by Steve Nicklas, NOS, NGS
The American Society of Civil Engineers’ 2025 Report Card for American Infrastructure, to which I contributed, assigned a D+ grade to the nation’s levees, citing aging infrastructure, inconsistent monitoring, and chronic underinvestment. A recent dataset created by my colleagues and I reveals 487 instances of levee overtopping in the past 15 years, indicating that many systems are operating with minimal safety margins.
How Levees Fail: A Cascade of Risks
Levee failures rarely occur as sudden, catastrophic collapses. More often, they begin subtly. The most common cause is overtopping – when water flows over the crest of the levee. This initiates erosion on the landward side, weakening the structure from within. What begins as a trickle can quickly escalate into a breach, allowing a surge of water to inundate surrounding areas.
S. Flynn et al., 2025
Atmospheric rivers significantly amplify these risks. These weather systems deliver immense rainfall over vast areas in short periods, often combined with snowmelt. Rivers rise rapidly and remain high for extended durations, exceeding the design capacity of many levees.
When a levee breaches, flooding can be swift and deep, leaving little time for evacuation and causing widespread damage. But who bears the brunt of these failures? The answer, unfortunately, is not evenly distributed.
Unequal Protection: The Human Cost of Levee Failure
Millions of Americans live and work in areas protected by levees, often unaware of the risk. Homes, schools, transportation networks, and critical infrastructure all rely on the integrity of these structures. However, a recent study reveals that urban expansion into floodplains has occurred at more than twice the rate in areas protected by levees compared to surrounding counties, suggesting a false sense of security.
The consequences of levee failure are often disproportionately borne by vulnerable communities. The March 2023 Pajaro River levee failure in California, which flooded the town of Pajaro, tragically illustrates this point. The town, home to many low-income farmworkers, experienced widespread devastation, with residents forced to evacuate and some trapped by rising waters. Investigations revealed that officials had known for decades about the levee’s vulnerabilities, but repairs were repeatedly delayed, in part due to financial constraints, as detailed by The Los Angeles Times.
Pajaro is not an isolated incident. Across the country, disadvantaged communities and communities of color are more likely to rely on older, less well-maintained levees. Rural towns often depend on agricultural levees, while urban neighborhoods may be protected by structures designed for a smaller population. When levees fail, the impacts cascade, disrupting lives for years.
F. Vahedifard et al., 2023
As we face a future of more frequent and intense storms, the question isn’t simply whether our levees are strong enough, but who we are protecting and at what cost. Do we prioritize investments based on economic value or equitable risk reduction? How do we communicate the inherent limitations of these structures to communities that rely on them?
These are difficult questions, but they are essential to address. The lessons of the past – from the Mississippi River floods of 1927 to Hurricane Katrina in 2005 – demonstrate the devastating consequences of neglecting our flood defenses and failing to prioritize vulnerable populations.
What role should federal, state, and local governments play in funding levee improvements? And how can we ensure that communities have a voice in decisions that directly impact their safety and well-being?
Frequently Asked Questions About Levee Safety
What is a levee and what does it do?
A levee is an embankment designed to prevent a river or other body of water from overflowing. They act as a barrier, protecting surrounding areas from flooding, but are not foolproof.
Why are so many levees aging and in need of repair?
Many levees were originally built decades ago with limited engineering standards and have suffered from years of deferred maintenance and underinvestment. Climate change is also accelerating their deterioration.
Are all levee failures catastrophic?
While levee failures can cause significant damage, not all breaches result in widespread devastation. The severity depends on factors like the height of the levee, the volume of water, and the preparedness of the community.
How does climate change impact levee vulnerability?
Climate change is increasing the frequency and intensity of extreme weather events, such as atmospheric rivers, leading to higher river levels and greater stress on levee systems.
What can be done to improve levee safety?
Improving levee safety requires increased investment in maintenance and upgrades, more robust monitoring systems, and a commitment to equitable risk reduction that prioritizes vulnerable communities.
Levees will remain a crucial component of flood protection for the foreseeable future. Understanding their history, limitations, and the disproportionate risks they pose to certain communities is paramount as we navigate an era of increasingly frequent and intense storms.
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