New Orleans Levee System: Failures, Oversight, and Subsidence

The New Orleans levee system is a $14.5 billion federal network of earthen levees, concrete floodwalls, surge barriers, gates, and pump stations that shields a city built largely below sea level from the Mississippi River, Lake Pontchartrain, and Gulf of Mexico storm surge. Rebuilt by the U.S. Army Corps of Engineers after Hurricane Katrina exposed catastrophic design flaws in 2005, it now spans more than 350 miles across five southeast Louisiana parishes and is engineered to defend against a 100-year storm — an event with a one percent chance of occurring in any given year.¹ Whether it can keep that promise through mid-century is now an open question, with sections of the system sinking up to an inch per year, federal maintenance funding in doubt, and the state’s signature coastal restoration project cancelled.

What the System Looks Like Today

The rebuilt defenses are formally called the Hurricane and Storm Damage Risk Reduction System, or HSDRRS. It encompasses more than 350 miles of levees and floodwalls, 73 non-federal pumping stations, three canal closure structures with pumps, and four gated outlets.² The design is coordinated rather than piecemeal, using barrier structures to block surge before it reaches interior areas. Concrete T-walls replaced the I-walls that failed during Katrina. Stability berms and deeper pile foundations were added. Pump stations received fronting protection: gates and walls that keep them operational during storms rather than allowing them to be swamped.

The Lake Borgne Surge Barrier

The centerpiece is the Lake Borgne Storm Surge Barrier, sometimes called the “Great Wall of Louisiana.” Completed in 2013 at a cost of $1.3 billion, it is the largest civil-works design-build project in Corps history. The barrier is 1.8 miles long and rises 26 feet above sea level. It sits at the confluence of the Gulf Intracoastal Waterway and the closed Mississippi River Gulf Outlet, precisely where a funnel effect had amplified Katrina’s surge into the city.³ The structure is anchored by 1,071 soldier pilings, each 140 feet long, with battered piles extending 200 feet underground. It includes a 150-foot-wide sector gate, a bypass barge gate, and a 56-foot-wide vertical lift gate.

The West Closure Complex and Canal Closures

On the West Bank, the West Closure Complex houses what has been described as the world’s largest interior drainage pump station. It features a 225-foot-wide navigable sector gate and 11 pumps capable of discharging 19,140 cubic feet per second. It is designed to block storm surge while continuing to pump interior rainwater out into the Gulf Intracoastal Waterway.⁴

The final major component, the Permanent Canal Closures and Pumps system, came online in May 2018. It replaced temporary structures built in 2006 at the mouths of the three outfall canals that had breached during Katrina: the 17th Street, Orleans Avenue, and London Avenue canals. Permanent gated storm surge barriers and pump stations now sit at those canal mouths, capable of moving a combined 24,300 cubic feet per second.⁵ Louisiana coastal officials have credited the improvements with preventing a repeat of Katrina during later storms; a retrospective analysis found that without them, Hurricane Isaac in 2012 could have caused levee failures and damages of similar magnitude.⁶

Why the Pre-Katrina System Failed

Hurricane Katrina made landfall on August 29, 2005. The hurricane protection system failed at multiple points, and roughly 80 percent of the city flooded. The breaches occurred at the 17th Street Canal, London Avenue Canal, and the Inner Harbor Navigation Canal, among other locations, with floodwaters reaching depths of up to 20 feet in surrounding parishes.⁷⁸

The American Society of Civil Engineers’ external review panel identified two immediate causes. Concrete “I-wall” floodwalls failed because designers had used an insufficient margin of safety, failed to account for the variability of soft organic soils beneath the structures, and did not anticipate the formation of water-filled gaps behind the walls as they bowed outward under pressure. And many levees lacked erosion protection, so when storm surge overtopped them the highly erodible soil scoured away and the structures collapsed.⁹

Deeper systemic problems magnified those failures. The system had been built piecemeal over decades rather than as an integrated structure. Levees were designed based on meteorological conditions less severe than what the National Weather Service had documented for a major Gulf Coast hurricane. Many structures were one to two feet lower than intended because they were built to an incorrect elevation datum, and designers had not compensated for the region’s ongoing land subsidence. Pump stations critical for removing floodwater were inoperable during and after the storm, and the system had never been subjected to rigorous independent peer review.⁹ Review panels characterized the pre-Katrina infrastructure as a “system in name only.”⁷

The Mississippi River Gulf Outlet, or MRGO, worsened the disaster. The 76-mile shipping channel opened in 1963, and between then and 2005 erosion had expanded its width from 635 feet to roughly 2,000 feet, destroying an estimated 23,000 to 65,000 acres of wetlands that had served as a natural buffer against storm surge. During Katrina, the MRGO and its paralleling levees created a funnel effect that amplified surge into the city, contributing to catastrophic breaching along the Inner Harbor Navigation Canal and the flooding of the Lower Ninth Ward and St. Bernard Parish.¹⁰ The Corps completed a rock closure across the MRGO in 2009, ending large-vessel navigation.

Estimates of Louisiana’s death toll from Katrina range from at least 986 to approximately 1,170 residents, depending on the study and methodology.¹¹⁸ Drowning accounted for about a third of deaths; acute and chronic diseases accounted for nearly half, reflecting the toll on elderly and medically vulnerable residents trapped by floodwater. Total damages from Katrina were estimated at $135 billion in 2005 dollars. In New Orleans, 134,000 housing units — 70 percent of all occupied units — were damaged.

Was Anyone Held Responsible

Thousands of plaintiffs sued the federal government. Their claims were consolidated as In re Katrina Canal Breaches Consolidated Litigation in the U.S. District Court for the Eastern District of Louisiana, alleging that the Corps’ negligent design, construction, and maintenance of levees caused their losses.¹² Over several years, two legal doctrines largely shielded the government from financial liability.

The first is immunity under Section 702c of the Flood Control Act of 1928, which provides that “no liability of any kind shall attach to or rest upon the United States from any damage from or by floods or flood waters.” The Fifth Circuit ruled that this immunity applied to the Lake Pontchartrain and Vicinity levees because they were flood-control structures, barring claims related to the breaches of the 17th Street, London Avenue, and Orleans Avenue canals.¹³

The second is the discretionary function exception to the Federal Tort Claims Act, which prevents suit when the challenged conduct involves policy judgments. U.S. District Judge Stanwood Duval Jr. had initially ruled for residents on claims related to MRGO in November 2009, awarding $720,000 in damages and finding that the Corps could not claim discretionary function immunity because its failures contravened professional engineering standards.¹⁴ The Fifth Circuit reversed in September 2012, holding that the Corps’ decisions regarding MRGO maintenance were “susceptible to policy analysis” and that the exception “completely insulates the government from liability.”¹³

A separate takings case brought by St. Bernard Parish and individual property owners went to the U.S. Court of Federal Claims, which in 2011 found the Corps liable for a temporary taking related to MRGO’s effect on storm surge and awarded approximately $5.5 million. The Federal Circuit reversed that ruling in April 2018, holding that the plaintiffs had failed to account for the risk-reducing effects of the Lake Pontchartrain levee project in their causation analysis.¹⁵ Judge Duval, in one of his rulings, noted: “The bureaucratic behemoth that is the Army Corps of Engineers is virtually unaccountable to the citizens it protects despite the Federal Tort Claims Act.”¹²

After Katrina, Congress authorized an ecosystem restoration plan for the MRGO area, made 100 percent federally funded by the Water Resources Development Act of 2022, with an estimated cost of $1.3 billion for the initial phase.¹⁶

Interior Drainage: The Other Half of the Problem

Levees stop surge and river water from coming in. They do nothing about rain that falls inside them. Because New Orleans sits in basins behind its protective walls, rainwater cannot drain naturally and must be pumped out, primarily into Lake Pontchartrain. The Sewerage and Water Board of New Orleans operates 24 drainage pumping stations housing 120 pumps, along with roughly 90 miles of open canals and 90 miles of subsurface canals.¹⁷

Much of this system has a distinctive and problematic vulnerability. It runs on 25-hertz electrical power generated in-house by steam and combustion turbines dating as far back as 1915. The commercial grid supplies 60-hertz power, so the city’s legacy drainage pumps cannot simply plug into Entergy’s grid.¹⁸ The S&WB has characterized running critical infrastructure on century-old equipment as “not sustainable.”

The fragility of that arrangement showed in the summer of 2017. A fire knocked out a key turbine on August 9, cutting power to a majority of East Bank drainage stations just days after severe flooding events on July 22 and August 5.¹⁹ Mayor Mitch Landrieu declared an emergency, the city allocated $22 million for drainage improvements, and workers scrambled to connect 26 portable generators. As of March 2021, the system required 52 megawatts of electricity for full capacity but relied heavily on backup diesel generators that had been promoted from emergency reserves to “front line” equipment.²⁰

The S&WB is constructing a Power Complex to modernize the system, drawing power from Entergy’s grid via a dedicated substation and using static frequency changers to convert it to 25 hertz for legacy pumps. Phase 1, estimated at $255 million, was targeted for completion by the 2025 hurricane season. Phase 2, estimated at an additional $50 million, is anticipated for late 2026 depending on funding.¹⁸

Who Runs the Levees Now

Before Katrina, New Orleans-area levees were managed by local levee boards widely criticized as parochial and politically connected. The Orleans Levee Board, in particular, was known for managing properties unrelated to flood protection. In the wake of the disaster, the Louisiana legislature consolidated the individual boards into two regional entities: the Southeast Louisiana Flood Protection Authority-East, covering Orleans, Jefferson, and St. Bernard Parishes, and the Southeast Louisiana Flood Protection Authority-West, covering the West Bank.²¹ The restructuring, established by constitutional amendment and Act 1 of the 2006 First Extraordinary Session, was designed to base flood protection on hydrologic basins rather than political boundaries and to require professional qualifications for board members.

Under the reformed structure, the governor appoints board members from nominations provided by an independent committee of experts drawn from engineering, academic, and civic organizations.²² The East Bank authority has nine commissioners; the West Bank has seven. Both boards require a supermajority of members with engineering, science, or other professional expertise. Strict ethics rules prohibit conflicts of interest and political campaign activity.

These reforms have faced recurring political pressure. In 2025, advisers to Governor Jeff Landry alleged that flood protection infrastructure had not been properly maintained and that dedicated funding had been wasted, though the Bureau of Governmental Research reported that no evidence supported those claims.²³ The governor’s office sought to reshape the East Bank authority, initially proposing to scrap the independent nominating committee and allow the governor to handpick board members. Four board members resigned in protest, leaving the authority without a quorum as of mid-2025.²⁴ The resulting legislation, HB688, passed both chambers unanimously on June 11, 2025, but in significantly scaled-back form. It preserved the independent nominating committee, added a seat for the executive director of the Coastal Protection and Restoration Authority, and extended board member eligibility to three consecutive terms from two.

The Levees Are Sinking

A study published in Science Advances in June 2025, led by researchers from Tulane University and the Jet Propulsion Laboratory at Caltech, used satellite radar data to measure land elevation changes across Greater New Orleans. Most of the city is generally stable, but the study identified significant elevation loss at specific locations. Sections of the HSDRRS flood protection infrastructure are subsiding at rates up to 28 millimeters per year — roughly an inch — and localized areas within the city are sinking at up to 20 millimeters per year.²⁵²⁶ Wetlands northeast of the city, particularly the Bayou Bienvenue Central Wetland Unit, are losing elevation at rates of 30 to 47 millimeters per year and risk becoming open water.

The subsidence is occurring faster than the Corps originally projected. Researchers attributed the sinking to natural sediment compaction, groundwater pumping for industrial and drinking-water use, land-use changes, and the oxidation of organic soils in former wetlands.²⁶ In practical terms, earthen levees in areas including New Orleans East, Kenner, and the West Bank are settling at about one inch per year. That means they require periodic “levee lifts” — adding soil to restore their design height. The Southeast Louisiana Flood Protection Authority East expects to contribute more than $300 million toward these lifts, with total upgrade costs estimated in the billions of dollars.²⁷

Funding and Federal Uncertainty

The Corps maintains that the HSDRRS is designed to provide 100-year storm surge protection through 2057, provided there is funding to periodically lift earthen levees. The Corps is studying how to extend that protection through 2073.²⁸ As of 2025, both the funding and the institutional capacity to perform that maintenance are in question.

While the federal government built the HSDRRS, responsibility for maintaining it was transferred to the Southeast Louisiana Flood Protection Authority. The authority depends on the Corps for levee inspections, and the Corps reported in 2025 that it lacks the funding to perform those inspections for 2025 or 2026.²⁹ The Trump administration’s proposed fiscal year 2026 budget cut the Corps’ civil works program by more than 24 percent, from $9.6 billion enacted in fiscal year 2024 to $7.2 billion. The Corps has offered early retirement to roughly 1,068 employees and closed several office locations.³⁰

At the state level, Governor Landry has cut funding for levee maintenance line items and moved to consolidate influence over the flood protection board. In August 2025 the state cancelled the $3 billion Mid-Barataria Sediment Diversion project, which would have used Mississippi River sediment to rebuild up to 27 square miles of protective marsh in Plaquemines Parish by 2050. The Coastal Protection and Restoration Authority cited rising costs, permitting concerns, and ongoing litigation in declaring it “no longer viable.”³¹ Coastal advocates argued the project would have “given New Orleans another generation” of protection. A smaller alternative diversion under consideration could take eight to ten years to approve and may not match the scale needed.³²

The Retreat Question

Subsidence from below, rising seas from above, and eroding wetlands on every side have prompted increasingly stark assessments from researchers. A 2026 perspectives paper published in Nature Sustainability by Jesse Keenan of Tulane University and co-authors argued that coastal Louisiana has “evidently already crossed the point of no return” and that New Orleans “may well be surrounded by the Gulf of Mexico before the end of this century.”³³ The paper described southern Louisiana as “the most physically vulnerable coastal zone in the world,” facing three to seven meters of sea level rise and the loss of three-quarters of remaining coastal wetlands, which would push the shoreline up to 100 kilometers inland.³⁴

The study called for immediate planning for a “managed retreat” of population and capital to safer ground, beginning with the most vulnerable communities. Keenan estimated the timeframe for necessary relocation as “decades rather than centuries.”³³ NPR later issued a correction noting that the study does not specify a precise timeline for the city to be surrounded by the ocean, and Keenan acknowledged “the real question is when and what does it mean to begin to plan a transition.”³⁵

The paper has drawn both agreement and pushback. Timothy Dixon of the University of South Florida acknowledged the study’s strengths but cautioned that the city will not disappear in a decade, while noting that policymakers should have initiated relocation planning much earlier. Louisiana-based critics argued the study underestimates the region’s capacity for reform, contending that ending property tax exemptions for petrochemical facilities, enforcing laws requiring oil and gas companies to remediate pipeline canals and abandoned wells, and investing in community resilience could make the region “too prosperous to move,” treating the paper as a call for reform rather than for abandonment.³⁶

What is not seriously disputed is the underlying trajectory. Louisiana has lost roughly 2,000 square miles of land since the 1930s, with an additional 3,000 square miles projected to vanish over the next 50 years. The levee system currently requires at least $1 billion in upgrades to remain sufficient, the Corps can offer no guarantees about congressional funding for improvements beyond the 100-year standard, and the state’s signature coastal restoration project has been cancelled.²⁸ The levees standing today are, by most accounts, far superior to what failed in 2005. Whether they can keep pace with what is coming is the question that now defines the system’s future.

1
U.S. Army Corps of Engineers. HSDRRS Overview
2
U.S. Army Corps of Engineers. HSDRRS Fact Sheets
3
Flood Protection Authority – East. Lake Borgne Surge Barrier
4
U.S. Army Corps of Engineers. Corps of Engineers Closes and Operates West Closure Complex for the First Time
5
Water Collaborative Delivery. Permanent Canal Closures and Pumps
6
Louisiana Coastal Protection and Restoration Authority. Two Decades After Katrina
7
National Academy of Engineering. Lessons From Hurricane Katrina
8
Louisiana Department of Health. Katrina Death Study
9
LSU Law Center. ASCE External Review Panel Report
10
64 Parishes. Mississippi River Gulf Outlet
11
The Data Center. Facts for Impact
12
Climate Case Chart. In Re Katrina Canal Breaches Litigation
13
U.S. Court of Appeals for the Fifth Circuit. In Re Katrina Canal Breaches Litigation, Nos. 10-30249 et al.
14
Christian Science Monitor. Army Corps Not Liable for Katrina Damage, Appeals Panel Finds
15
U.S. Court of Appeals for the Federal Circuit. Federal Circuit Holds U.S. Army Corps of Engineers Not Liable for Hurricane Katrina Flooding
16
U.S. Army Corps of Engineers. MRGO Ecosystem Restoration
17
Sewerage & Water Board of New Orleans. Stormwater Overview
18
Sewerage & Water Board of New Orleans. SWBNO Power Complex
19
City of New Orleans. SWB Power Incident
20
WDSU. Power Supply for New Orleans Drainage System Is Alarming Situation, S&WB Director Says
21
Southeast Louisiana Flood Protection Authority – West. SLFPA-W History
22
Louisiana Legislature. La. R.S. 38:330.1
23
Bureau of Governmental Research. BGR Statement on Flood Protection Authority Governance
24
NOLA.com. Jeff Landry, Louisiana, New Orleans Hurricanes and Flooding
25
Science Advances. Vertical Land Motion in Greater New Orleans
26
PMC/National Institutes of Health. Vertical Land Motion in Greater New Orleans
27
FOX 8 Live. Some Levees Are Sinking: Why One Levee Official Is Not Surprised
28
Grist. Katrina Levees New Orleans Army Corps Trump Landry
29
New Orleans CityBusiness. New Orleans Levees Sinking, Funding
30
Waterways Council. NWC Federal Spotlight
31
Louisiana Coastal Protection and Restoration Authority. State, Louisiana Trustee Implementation Group Announce Termination of Mid-Barataria Sediment Diversion
32
Verite News. Mid-Barataria, Gordon Dove, CPRA
33
The Guardian. New Orleans Sea Levels, Relocation, and Climate Crisis
34
Vox. New Orleans Sea Level Rise: Residents, Relocate
35
NPR. New Orleans Surrounded by Water
36
The Lens. Point of No Return: Time for a New Paradigm