New Orleans Sea Level Rise: Subsidence, Levees, and Managed Retreat

Sea-level rise in New Orleans is running faster than almost anywhere else in the United States, and a 2026 perspectives paper in Nature Sustainability concluded that coastal Louisiana has “crossed the point of no return,” with projections of three to seven meters (roughly 10 to 23 feet) of eventual rise that could leave the city surrounded by the Gulf of Mexico before the end of the century.¹ The city of about 360,000 people is caught between an ocean that is climbing and ground that is dropping, and the defenses built after Hurricane Katrina were not designed for the pace of change now underway.

How Fast the Water Is Rising

NOAA’s tide gauge at Grand Isle, Louisiana, shows a relative sea-level trend of 9.13 millimeters per year from 1947 to 2025, roughly three feet per century.² Global mean sea level, by comparison, has risen about eight to nine inches since 1880. The western Gulf coast from the Mississippi River west is projected to see 16 to 18 inches of rise above 2020 levels by 2050, about half a foot above the national average.³

The pace is picking up. NOAA’s National Sea Level Explorer shows Louisiana’s rate climbing from 2.0 inches per decade in the 1970s to 4.1 inches per decade in the 2020s, with a cumulative rise of roughly 17 inches since 1970. Under NOAA’s intermediate scenario, another 17 inches is expected between 2020 and 2050 alone, with about 1.1 feet of that coming from vertical land motion.⁴

Why the City Is Sinking at the Same Time

The water isn’t just rising. The land is dropping. Roughly half of the greater New Orleans area south of Lake Pontchartrain already sits below sea level.⁵ Lakeview and Gentilly lie five to eight feet under. Eastern New Orleans is 6 to 12 feet below. Broadmoor and Mid-City are three to seven feet down.⁶ These neighborhoods sank largely because drainage lowered the water table and the organic-rich soils oxidized and compacted.

The sinking continues. A NASA study using airborne radar between 2009 and 2012 found some industrial zones near Norco and Michoud dropping as fast as two inches per year, with the Upper and Lower Ninth Ward and Metairie also showing notable subsidence. Groundwater pumping, dewatering to keep the city dry, natural compaction of soft deltaic sediments, and the interruption of sediment supply by flood-control levees all contribute.⁷ Combined with climbing seas, the effective rate of water encroachment is far faster than either number alone suggests.

What the 2026 Study Actually Said

The May 2026 Nature Sustainability paper was co-authored by Tulane University’s Torbjörn Törnqvist and Jesse Keenan and Yale School of the Environment’s Brianna Castro.¹⁸ It synthesized existing science and drew a comparison to a period 125,000 years ago when global temperatures were 0.5 to 1.5 degrees Celsius above preindustrial levels and sea levels stood 10 to 20 feet higher than today. The shoreline from that era sits about 30 miles north of present-day New Orleans, just above Lake Pontchartrain.⁹

With global temperatures already approaching 1.5 degrees of warming and tracking toward about three degrees, Törnqvist argued the planet is “likely already locked in” for the shoreline to eventually retreat that far inland, threatening southern Baton Rouge as well.⁹ The paper projected the loss of roughly three-quarters of remaining coastal wetlands and inland shoreline retreat of up to 62 miles.¹ Separate research cited in the same reporting found 99% of New Orleans’ population lives in areas at major risk of severe flooding, the highest exposure of any U.S. city.⁸ The authors called the city’s condition “terminal” and the surrounding region “the most physically vulnerable coastal zone in the world.”

Can the Levees Keep Up

After Katrina’s levee failures in 2005, the federal government spent more than $14 billion on the Hurricane and Storm Damage Risk Reduction System, completed between 2012 and 2018. It includes nearly 200 miles of levees, the two-mile Lake Borgne Surge Barrier (designed for 26 feet of surge), and major pump stations, and it is built to “100-year” protection, meaning a storm with a one-percent annual probability. It held during Hurricane Ida in 2021, a Category 4 storm.¹⁰¹¹

The system is also aging in ways its designers did not fully anticipate. Parts of the levees are settling by nearly two inches per year while seas rise about half an inch annually, rates that exceed original design projections.¹⁰ The Army Corps of Engineers estimates that maintaining current heights over the next 50 years will cost more than $1 billion, including lifting 50 miles of levees and replacing or adding more than three miles of flood walls.¹² The original federal authorizations did not include that money, and the Corps has reported it currently lacks funding to inspect the levees in 2026.

Current estimates suggest the major concrete structures can hold their design capacity through 2057 if sea-level rise follows Corps projections. Without improvements, the system falls below 100-year protection by 2073, potentially making the region ineligible for federal flood insurance.¹² The system was never built to stop a Category 5 storm, and without natural buffers like wetlands, engineering alone cannot keep pace with the changes projected.¹⁰

Shrinking Natural Defenses

Since the 1930s, Louisiana has lost nearly 2,000 square miles of coastal land, an area roughly the size of Delaware.¹³ Under the state’s 2023 Coastal Master Plan, Louisiana could lose another 1,100 to 3,000 square miles by 2070 without further action.¹⁴ Barrier islands and marshes are the first line of defense against storm surge, and their disappearance exposes the levees, communities, and infrastructure behind them.

The state’s largest coastal rebuilding project is no longer going forward. In July 2025, Governor Jeff Landry’s administration terminated the $3 billion Mid-Barataria Sediment Diversion.¹⁵ The project would have reconnected the Mississippi River with the Barataria Basin, channeling 75,000 cubic feet of sediment-laden water per second to rebuild nearly 20 square miles of wetlands over 50 years. Landry argued it would devastate the fishing industry; the Oyster Task Force had long opposed it, contending that the $400 million mitigation budget was inadequate.¹⁶ The Army Corps had also suspended the federal permit in April 2025, citing sediment toxicity, fisheries impact, and flood-risk concerns.¹⁷

Over $600 million of the authorized budget had already been spent. The state is now pursuing a smaller replacement, the Myrtle Grove project, with a $278.3 million budget and a diversion capacity 5 to 30 times smaller.¹⁷ Analysts estimate it could take a decade or more to bring any replacement to where the original stood.¹⁶ The Nature Sustainability authors wrote that the cancellation “effectively means giving up on extensive portions of coastal Louisiana, including the New Orleans area.”¹

The broader Coastal Master Plan remains in place. The 50-year, $50 billion framework includes 73 proposed projects and anticipates at least 1.5 feet of global sea-level rise by 2070. Since 2005, $21.4 billion has been invested in completed projects, funded largely by BP settlement dollars from the 2010 Deepwater Horizon oil spill. That money is expected to run out within the next decade.¹⁴

What Rising Risk Means for Insurance and Home Values

The economics of living in New Orleans are already changing. Under FEMA’s Risk Rating 2.0, implemented in 2021 and 2022, flood insurance premiums are calculated based on individual property risk rather than flood zone maps. The Times-Picayune estimated an average premium increase of 122% for Louisiana under the new system, and the number of National Flood Insurance Program policies in force in the state has fallen by roughly 22,000 since October 2021.¹⁸ Gulf Coast states are absorbing the largest increases because their policies were historically the most underpriced relative to actual risk.¹⁹

Annual increases are capped by Congress at 18%, which creates a long glide path. The GAO projects a $27 billion premium shortfall before 95% of policies reach full-risk rates, likely around 2037. The NFIP already carries $36.5 billion in cumulative borrowing from the U.S. Treasury dating to 2005.¹⁹

For New Orleans homeowners, insurance already consumes 3.6% of a home’s market value annually, the second-highest ratio among the 100 largest U.S. metros. On a median-valued home of about $231,000, the estimated annual premium is more than $8,300. The city also leads the nation in the gap between homes FEMA formally designates as high-risk and homes that actually face severe or extreme flood danger: 88.9% of New Orleans home value, totaling $72.1 billion, is at risk of severe or extreme flood damage, but 66 percentage points of that risk falls outside FEMA’s Special Flood Hazard Areas.²⁰ Flood insurance policies in Louisiana overall fell 17% between August 2021 and July 2025, even as risk has grown.¹¹

The Debate Over Managed Retreat

The most provocative argument in the Nature Sustainability paper is that New Orleans must begin a coordinated, government-led relocation now to avoid what the authors call a “disordered” exodus driven by insurance costs and repeated flooding. Keenan proposed starting with the most vulnerable communities, particularly those in Plaquemines Parish living outside the levee system, and directing infrastructure investment toward land north of Lake Pontchartrain. Timothy Dixon of the University of South Florida said governments cannot force relocation but called “managed retreat” the “ultimate solution,” since residents will eventually volunteer to move when they can no longer insure their homes.¹

The study pointed to Kiruna, Sweden, as a model. That Arctic city of about 20,000 is being relocated two miles east to accommodate iron ore mining, with the process expected to conclude by 2033. The effort involves moving 3,000 homes under a master plan led by the municipal government in coordination with the state-owned mining company LKAB.²¹ The researchers acknowledged relocating a city of 360,000 would be far greater in scale, but argued the timeframe is “most likely decades rather than centuries.”¹

The One U.S. Precedent

The only federally funded climate relocation in the United States is the Isle de Jean Charles Resettlement Project in southern Louisiana. In 2016, the state received $48.3 million in federal Community Development Block Grant funds to relocate 37 families from a disappearing island to a new community called “The New Isle” in Schriever, about 40 miles north. Move-ins began in August 2022 into homes built above the 500-year floodplain.²²

Residents have since reported substandard conditions including leaking doors, malfunctioning appliances, and potential structural issues.²³ A former state official acknowledged the state was unprepared and faced a “very short timeline” to meet a 2021 federal spending deadline, which contributed to rushed construction.²⁴ The original plan to reunite the Jean Charles Choctaw Nation splintered when federal rules barred using tribal affiliation to determine housing eligibility. Experts have warned the new site itself could face future flooding as coastal land loss continues.

The U.S. Government Accountability Office has found that the country has no national strategy for relocating coastal communities and holds only limited funds to do so.²³ Louisiana’s state government currently has no further plans to assist with community-scale relocations.²⁴

Political Resistance

Government leaders have mostly avoided discussing what the paper’s authors call the “terminal” nature of the city’s future.¹ Christopher Ard, an 11th-generation New Orleanian, rejected the framing, arguing the city cannot be “relocated” and that such proposals amount to a “death sentence for those without the means to leave,” and advocating instead for strategies that extend the city’s life.²⁵

St. Tammany Parish on the Northshore, which the study identified as a logical receiver, has already been absorbing growth for decades. Between 2000 and 2020, the unincorporated parish grew by about 46%, reaching roughly 206,600 residents, and projections anticipate another 31,000 to 41,000 over the next 20 years. The parish’s comprehensive plan explicitly recognizes its role as a “receiver community” for populations displaced by disaster, while noting that rapid growth has already strained roads, drainage, and wastewater systems.²⁶

Where Things Stand

New Orleans has already lost about 25% of its population since Katrina, dropping from roughly 485,000 before the storm to about 360,000 today.⁸ That earlier exodus was unplanned and, for many who left, permanent. The scientific projections now suggest the question is whether the next retreat is managed or chaotic, and that the timeline for the answer is measured in decades rather than centuries.

1
The Guardian. Point of No Return: New Orleans Relocation Must Start Now
2
NOAA Tides & Currents. Relative Sea Level Trend, Grand Isle, Louisiana
3
NOAA Climate.gov. Climate Change: Global Sea Level
4
Earth.gov. National Sea Level Explorer – Louisiana
5
64 Parishes. Louisiana’s Place in the Below Sea Level World
6
Open Rivers Journal. New Orleans Was Once Above Sea Level
7
NASA Jet Propulsion Laboratory. New Study Maps Rate of New Orleans Sinking
8
CNN. Rising Seas Will Swallow New Orleans
9
Tulane University. Tulane Researchers Say Louisiana Could Lead Global Climate Adaptation Efforts
10
Grist. Shrinking Post-Katrina Levees Need Upgrades
11
PreventionWeb. Twenty Years After Katrina: Legacy of Risk and Resilience
12
E&E News. Shrinking Post-Katrina Levees Need $1B in Upgrades
13
Louisiana Coastal Protection and Restoration Authority. A Changing Landscape
14
WRKF. Louisiana Unveils Update to 50-Year, $50 Billion Plan to Restore Its Eroding Coast
15
Louisiana Coastal Protection and Restoration Authority. State, Louisiana Trustee Implementation Group Announce Termination of Mid-Barataria Sediment Diversion
16
Louisiana Illuminator. Environmentalists Lament While Oystermen Celebrate Demise of Mid-Barataria Diversion
17
Engineering News-Record. Louisiana Pulls Plug on $3B Sediment Diversion Project
18
Williams College. Risk Rating 2.0 and Its Impact on Southern Louisiana
19
U.S. Government Accountability Office. Flood Insurance: Comprehensive Reform Could Improve Solvency and Enhance Resilience
20
Realtor.com. 2025 Housing and Climate Risk Report
21
White Arkitekter. Kiruna Masterplan
22
Louisiana Office of Community Development. Isle de Jean Charles Resettlement Project
23
Louisiana Illuminator. Climate Relocation Cautionary Tale
24
Mother Jones. America’s First Attempt to Tackle Climate Relocation Sparks Regret
25
The Lens. Point of No Return: A Conversation About Sea Level Rise and the Future of New Orleans
26
St. Tammany Parish. New Directions 2040 Comprehensive Plan