On May 15, 1928, President Calvin Coolidge signed the Flood Control Act into law. It was the most expensive and comprehensive piece of legislation Congress had ever passed, committing the federal government to ensuring that no flood like 1927 would happen again. The Army Corps of Engineers would build, maintain, and operate a system of levees, floodways, and spillways along the entire lower Mississippi. The river would be contained.
Buried in the Act was Section 702c:
"No liability of any kind shall attach to or rest upon the United States for any damage from or by any floods or flood waters at any place."
The consequences are physical, measured in square miles of land that no longer exists, and legal, measured in claims that courts have refused to hear. Both run through the same geography.
The Sediment
The Mississippi River built southern Louisiana. For seven thousand years, seasonal floods carried sediment from thirty-one states across the river's floodplain, depositing layers of silt that created and sustained the delta's wetlands. The cycle was continuous: floods delivered sediment, marshes grew, subsidence pulled land downward, the next flood replenished it. The river wandered, building new lobes of delta as old ones subsided, maintaining a rough equilibrium.
Levees along the lower Mississippi predated the 1928 Act by decades. The Mississippi River Commission had championed a levees-only doctrine since the 1880s, and by 1927 hundreds of miles of earthen walls already lined the river. The 1928 Act actually represented a partial break from that orthodoxy, incorporating spillways like Bonnet Carré and floodways like Birds Point-New Madrid alongside the levees. But the Act federalized and vastly expanded the existing system, sealing the river from its floodplain more completely than any previous effort. The sediment consequences belong to the entire levee regime, which predates 1928 by decades. The Act accelerated and made permanent what had already begun.
Walls of earth and concrete cut the river off from the delta. Sediment that had built the coast now shot past it, deposited into the deep Gulf of Mexico where it sustained nothing. The amount reaching the delta has declined by more than 70 percent since 1850, driven by levee construction and upstream dam-building in roughly equal measure.
The consequences are quantified with unusual precision. Since the 1930s, Louisiana has lost approximately 2,000 square miles of coastal land, an area the size of Delaware. The state contains roughly 40 percent of the nation's wetlands and accounts for 90 percent of coastal wetland loss in the lower forty-eight states. At peak rates in the 1970s, land vanished at nearly 33 square miles per year. A 2017 USGS analysis found Louisiana lost 58 square miles between 2010 and 2016 alone.
A 2023 study in Nature Sustainability, led by researchers at LSU and Indiana University, apportioned the causes across the full history of intervention:
| Cause | Share of Delta Land Loss |
|---|---|
| Levee construction | ~40% |
| Subsurface oil and gas extraction | ~40% |
| Upstream dam-building | ~20% |
The levees alone created an annual basin-wide sediment deficit producing land loss of roughly seven square kilometers per year.
The Atchafalaya Basin, where sediment flow was never fully severed, is the only region of coastal Louisiana currently building deltaic wetlands. The Terrebonne Basin, where levees cut off Mississippi River sediment in 1903, has experienced some of the most drastic land loss in the state.
Today, less than 10 to 15 percent of Louisiana's deltaic coast is maintained by the river. Without intervention, an additional 10,000 to 13,500 square kilometers of coastal Louisiana will be lost by 2100 due to subsidence and sea level rise.
The Immunity
The legal consequence of the 1928 Act surfaced eighty years later, in the same parish that had absorbed the cost of flood management decisions in 1927.
In April of that year, as floodwaters threatened New Orleans, Louisiana's governor authorized the dynamiting of the levee at Caernarvon, south of the city, to divert water through St. Bernard and Plaquemines parishes and relieve pressure on the metropolis. The decision destroyed the livelihoods of thousands of residents, mostly trappers and fishermen. Claims totaling $35 million were eventually reduced to $2.9 million in settlements, most of it paid to a fur company. Judge Meraux of St. Bernard Parish called it "the public execution of this parish."
In August 2005, Hurricane Katrina devastated the same community. The Mississippi River-Gulf Outlet, a 76-mile navigation channel built by the Army Corps of Engineers in the 1960s, had funneled storm surge directly into St. Bernard Parish and the Lower Ninth Ward. Known locally as MRGO, the channel had been eroding protective wetlands for decades. Residents and scientists had warned about the danger for years.
The litigation that followed split into two streams, each blocked by a different legal barrier.
For claims arising from the failure of the outfall canal levees along the 17th Street, Orleans Avenue, and London Avenue canals, the court ruled in January 2008 that the 1928 Act's immunity provision applied. Those were flood control structures. Section 702c barred the claims outright.
The MRGO claims took a different path. After a 19-day bench trial, Judge Stanwood Duval of the Eastern District of Louisiana found the Corps negligent. His November 2009 ruling determined that the Corps' failure to maintain the MRGO was "a substantial cause" of the levee failure that flooded St. Bernard Parish. He rejected the Corps' claim of immunity under Section 702c, reasoning that the MRGO was a navigation channel, not a flood control project. He awarded $719,000 to five plaintiffs. He described the Corps' negligence as "gross."
The MRGO plaintiffs had cleared the 1928 Act's barrier. They had won at trial. Then the Fifth Circuit Court of Appeals reversed. In its 2012 ruling, the appellate court agreed that Section 702c did not apply to the MRGO claims. But it ruled that the Federal Tort Claims Act's discretionary function exception shielded the Corps instead. The Corps' decisions about maintaining the channel, even decisions a trial court found grossly negligent, constituted protected government discretion. The Center for Progressive Reform described the reversal as "Judge Smith's breathless hairpin turn," noting that the same three-judge panel reversed a position it had taken only six months earlier.
Two different doctrines, applied in sequence. No plaintiff recovered.
Duval, in a related ruling, offered an observation that reads as epitaph:
"The bureaucratic behemoth that is the Army Corps of Engineers is virtually unaccountable to the citizens it protects despite the Federal Tort Claims Act. The public fisc will very possibly be more jeopardized by a lack of accountability than a rare judgment granting relief."
The Through-Line
St. Bernard Parish was dynamited in 1927 to protect New Orleans. Its residents received pennies on the dollar. The same parish was flooded in 2005 through a channel the Corps built and failed to maintain. Its residents recovered nothing. The legal architecture that prevented recovery traces to the legislation written in response to 1927.
The river is still contained. The delta is still subsiding. And Section 702c remains on the books.