POINTE-AUX-CHENES, La. — Earl Billiot guides his boat down a quiet bayou and explains how it used to be, when the water that runs as wide as a two-lane highway was so narrow you could reach out and touch the land. Branches heavy with Spanish moss draped over the bayou, and forests covered marshes that are bare now except for the bony skeletons of dead cypress trees.

POINTE-AUX-CHENES, La. — Earl Billiot guides his boat down a quiet bayou and explains how it used to be, when the water that runs as wide as a two-lane highway was so narrow you could reach out and touch the land. Branches heavy with Spanish moss draped over the bayou, and forests covered marshes that are bare now except for the bony skeletons of dead cypress trees.

Eighty miles away, tourists and locals gather atop a levee in New Orleans to gape at the magnificent Mississippi River, swollen by floods and higher than most have ever seen it. They relax in the afternoon sun with plastic cups of daiquiris and beer, certain that the structure they sit on will keep the water back.

Two worlds, each dependent on the Mississippi River, each facing a far different future as a result of the levees put in place generations ago to protect land along the waterway. They've done their job, but for decades they also have deprived the world's seventh-largest delta of land-sustaining sediment by funneling it straight into the Gulf of Mexico. From 1932 to 2000, some 1,900 square miles of land were lost and replaced by seawater. At the current rate, scientists say more than 500 additional square miles will be gone by 2050. By 2100, they say New Orleans could be little more than an island.

If there's one thing environmentalists, politicians and locals like those living in Pointe-aux-Chenes agree on, this year's floods have proved that something has to change.

"Right now there's a historic flood carrying record amounts of sediment, and we have no way to capture any of it," David Muth of the National Wildlife Federation said at a conference this month in New Orleans that brought together scientists, politicians and lobbyists to discuss ways of reversing land loss. "It is ridiculous that we're sitting here and all that sediment is going past, and most of it is going to be lost."

"The waste that is occurring ... is not to be described," said R. King Milling, a former banker who is chairman of the America's WETLAND Foundation. "Saving this coastline has economic ramifications that are just astonishing for the rest of this country," said Milling, warning of the potential damage to industries that survive off the delta's land and water, from seafood to oil and natural gas.

The problem of sediment deprivation isn't a surprise. As far back as the late 1800s, engineers seeking ways to prevent the river from swallowing communities were debating whether to adopt a levee-only system, as opposed to one that would combine levees with outlets to allow the river to run free in spots and disperse sediment.

But devastating floods in 1927, which killed nearly 250 people and displaced 700,000, ramped up the urgency to tame Mother Nature, leading to the levee-dominant system. Climactic catastrophes such as Hurricane Katrina in 2005 and this year's floods have added urgency to efforts to address the loss of land due to lack of river sediment. Hurricanes can more easily send the sea — rising as a result of climate change — washing over the delta and further upending the ecosystem.

Finding the solution has proved daunting in the face of competing interests. Environmentalists balk at drastic sediment-diverting measures they say could harm wildlife; oystermen and others who live off the sea worry that altering the river's flow could disturb the salinity their oyster beds need to thrive; the Army Corps of Engineers says restoring lost land could affect navigation on the waterway and that any diversion plans need careful study; politicians complain that they're hamstrung by federal studies, environmental impact requirements and lack of money.

"Somehow, some way, we'd better fast-track this," said Billy Nungesser, president of Louisiana's Plaquemines Parish. Nungesser's idea in the short term is to lease a dredge that would work 24/7 at the river's mouth to capture sediment for land restoration, and federal approval of a master plan for gulf restoration that would grant emergency permits for work to start quickly.

Nungesser also advocates building berms and rebuilding barrier islands and says projects could be funded through private investments and from billions of dollars in penalties expected from BP for last year's Deepwater Horizon oil spill. The amount of the penalties has not been determined, and it will be separate from the $20 billion fund established to compensate individuals and businesses hurt by the spill.

But getting access to the penalty funds is dependent on a bill sponsored by Louisiana senators to direct 80 percent of the BP payouts directly to the Gulf Coast for natural resource restoration. Currently, the fines, whose exact amount is not yet determined, are to go into the U.S. Treasury.

"We've got a window of opportunity, and we'd better not screw it up. We need to have some sense of urgency if we're going to save our coast," Nungesser said.

Other plans that have been floated for years by the science and engineering communities tend toward the more ambitious, expensive, and time-consuming: everything from creating a new mouth for the Mississippi to creating channels through existing levees to release sediment or using pumps and tunnels to capture sediment and steer it to areas in need of land restoration.

"The debate is more engineering versus less engineering," said Christopher D'Elia, dean of the School of the Coast and Environment at Louisiana State University. "There are a lot of people who just want to build more levees and dikes and control (the river) that way, but the people who understand sediment dynamics understand that's not going to work."

Ultimately, he said the solution may be to let the river run wilder, which would build land but displace people and industry in the water's way. "But how do you manage that socially? How do you recover the social and economic loss that occurs?" D'Elia said. "That's the challenge we're in right now. We're absolutely hamstrung by this situation."