The muddy slop dredged from the canals had to go somewhere. Oil companies piled it where they found it, creating an estimated 13,000 miles of tide-blocking spoil banks.
R. Eugene Turner, an LSU oceanographer, has calculated that every square mile of the delta is bounded on three sides by oil-canal ridges. Turner has spent more than 30 years studying the oil industry's footprint on the delta.
"If the water is blocked from going in, the wetlands on other side is drier for a little longer and also stays flooded longer than it otherwise would be," Turner said. "By drying it, the land oxidizes and dries out; and if it's wetter, it's like leaving a lawn sprinkler on and the plants are going to die."
The damage doesn't stop with the canals. For example, U.S. Geological Survey scientists say the sucking out of the ground of so much oil and gas likely caused the land in many places to sink by half an inch a year. In oil's heyday 30 years ago, Louisiana's coastal wells pumped 360 million barrels a year, an eighth of what Saudi Arabia ships to the market today.
Oil wells also discharged about a billion gallons daily of brine, thick with naturally occurring subsurface chemicals like chlorides, calcium and magnesium, as well as acids used in drilling.
"It was poured into the marshes," said Virginia Burkett, a longtime researcher of the Louisiana wetlands and the chief scientist for climate change at USGS. It contaminated soils and killed plants and animals, she said, before brine dumping was finally regulated in coastal marshes in 1985.
Still, when politicians in Washington or Louisiana talk about Katrina guilt they blame the Corps of Engineers, global warming and the French for building a city in low-lying swamps nearly 300 years ago — but not the oil industry.
"It's the elephant at the dinner table and nobody wants to say there's an elephant there," said Luke Fontana, a New Orleans lawyer for Save Our Wetlands, one of the state's oldest grassroots environmental groups that has fought the draining of swamps and oil company activity since the 1970s.
But the industry's legacy is getting new attention. Some contrast record petroleum profits with staggering cost estimates — up to $60 billion — to save New Orleans and restore the delta. In 2006, major U.S. oil companies, some of which moved offices from New Orleans to Houston, earned about $162 billion.
Meanwhile, locals increasingly ask why oil shouldn't be made to clean up its profitable mess the same as mining operations had to do in Appalachia.
Delta folks like Griffin, the grocer in Leeville, wonder why Shell, ExxonMobil and other oil behemoths aren't paying for the disappearance of his boyhood duck ponds and dune-lined islands.
"It seems that the government should hold them accountable for some of the problem," Griffin said from behind his cash register.
At mid-20th century, marsh-borne oil derricks towered over Leeville's shacks as far as the eye could see, replacing fields of cotton. Today, those same places, chopped up by bucket dredges, are open water. A town cemetery lies in the water, its tombs barely visible. And as Leeville goes under, New Orleans, 50 miles to the northeast, becomes that much more exposed.
The oil industry has not gone entirely unchallenged.