“It’s a lot,” she said, enough to cover 60 square miles half an inch deep every year, an amount that would slow or even reverse land loss in the state’s marshes, which have shrunk by about a quarter, more than 1,500 square miles, since the 1930’s. Such a program would not turn things around immediately, “but every year new land would be built,” said Joseph T. Kelley, a professor of marine geology at the University of Maine, who took part in the April meeting.

As the bird-foot delta broke up, Dr. Reed said, it would provide needed sediment to the frail strings of barrier islands that line some of the Louisiana coast.

Another potential benefit, Mr. Hanchey said, would come from the substantial nutrient runoff from inland agriculture in chemicals that contribute to the so-called dead zone of oxygen-poor water near the river’s mouth. Applied to the marsh, the nutrients might encourage desirable plants, he said.

Designing such a diversion would be complex and time-consuming, and the experts who met in April did not even attempt it. Even this fall’s meeting is not to plan the project, but to plan how the project should be planned, Mr. Hanchey said. Though Louisiana is rich in experts on river, wetland and coastal science, he said, state officials hoped to recruit scientists and engineers from all over the world to tell them “what we would have to know before we could initiate work on something like this, and what we would have to do to gain that knowledge.”

In a way, the bird-foot delta is an artifact of engineering. Without the levees and other structures that keep the river in place, it probably would have taken another path.

Like many major rivers, the Mississippi has tributaries, which feed water into it, and distributaries, which carry water away from it as it nears its mouth. Its tributaries include the Missouri and Ohio Rivers; one way or another, every stream, storm drain and parking lot from the Rockies to the Appalachians drains into the Mississippi. But about 250 miles from the gulf, near Lettsworth, La., the river stops taking water in and starts feeding it out, into the gulf through the main stem of bird-foot delta but also in distributaries like the Atchafalaya River, which flows into Atchafalaya Bay to the west.

Until people interfered with its flow, the Mississippi’s path to the gulf silted up naturally over time; water flow slowed and the river bed lost its capacity to carry a big flood. When next the big flood came, the river would suddenly turn one of its distributaries into its new main stem.