NEW ORLEANS, La. — A small breach on the marsh-covered east bank of the Mississippi River south of New Orleans is giving rise to calls to let the river run wild.

The debate centers on a 77-foot-wide channel the river carved through a levee road in the unused Bohemia spillway in Plaquemines Parish, about 45 miles south of New Orleans. The breach is outside levees that protect thinly populated communities on the sliver of delta that extends south to form Louisiana’s boot.

Scientists for the Lake Pontchartrain Basin Foundation, a New Orleans-based environmental group, say the new channel formed in February, during Mardi Gras season. They’ve dubbed it “Mardi Gras Pass.”

The scientists are urging that the breach be allowed to remain, saying restorative, land-building silt it is pouring into marshes.

“We believe it is a river itself, a branch of the river,” said John Lopez, the foundation’s executive director.

The debate is not limited to academic theory.

Since the 1930s, the Mississippi through south Louisiana has been confined by levees. But the levees, designed to keep population centers safe from catastrophic flooding, also starved marshes and swamps of the delta of sediment and fresh water. Eight decades later, surveys show erosion has set in at alarming rates.

According to the U.S. Geological Survey, south Louisiana, home to the nation’s largest coastal marshland, is washing away at a rate of more than 11 square miles a year — about one football field every hour.

To reverse the land loss and restore the area’s hurricane storm-surge buffer, the state is pushing a 50-year, $50 billion master plan to rebuild barrier islands and shorelines and recreate ridges. One element of the plan would divert the Mississippi into basins and sub-deltas that have been starved of freshwater and sediment.

That’s where the new channel comes into play.

On June 29 environmental groups, including the Environmental Defense Fund, the National Audubon Society, the National Wildlife Federation and Tulane University, petitioned the Army Corps of Engineers to stop an oil company from repairing the elevated road in the Bohemia Spillway that was washed out by the breach.

In January the Army Corps gave Houston-based Eland/Sundown Energy permission to rebuild the road, which leads to a facility in the spillway. The company did not return telephone calls seeking comment.

“A road repair would now be in effect a damming of a river,” Lopez said.

This new channel, the environmental groups argue, can act as a permanent river diversion that could help restore natural order in the delta.

And, they say, the breach can do the work of the manmade diversion contemplated in the state’s master plan. The plan’s proposed diversion, called the Lower Breton diversion, would be constructed near to where the Bohemia spillway was breached. The state estimates the building cost at $212 million.

The scientists’ idea may be gaining some traction.

Garret Graves, Gov. Bobby Jindal’s top coastal aide, said the state is examining the breach matter.

“We need to continue to work to restore the historic distributaries of the Mississippi River in a manner that will help to protect south Louisiana communities for the long-term,” Graves said. He added that the breach in Bohemia spillway was more evidence that “the Mississippi River does not want to stay confined to the banks.”

Keeping the river-made cut open could, over time, funnel the kind of water and sediment that the Lower Breton diversion would do, Lopez argued.

Although the channel is pushing only meager amounts of water now (between 440 cubic feet per second to 2,400 cubic feet per second), Lopez said the breach is expected to widen and deepen.

State engineers propose to build the Lower Breton diversion about 1 mile from the Mardi Gras Pass cut. Under their plan, the manmade diversion would be capable of carrying as much as 50,000 cubic feet of water per second.

Lopez said he believes the Bohemia channel could carry an amount of water similar to the proposed diversion.

Meanwhile, the Army Corps is reviewing the environmental groups’ road request, said Ricky Boyett, a corps spokesman. The agency is being asked to revoke the permit issued in January to allow the company to rebuild the road.

Before declaring a waterway navigable — and therefore subject to rules and laws designed to keep the waterway free-flowing — the Army Corps would be required to prepare engineering and legal reports.

For now, the corps says water flowing through Mardi Gras Pass poses no risk to navigation on the Mississippi.

The breach’s location makes for an interesting back story.

The Bohemia spillway is a 330,000-acre swath of marshland expropriated by the Orleans Levee Board in a controversial move in 1924. The spillway was meant to help protect New Orleans from flooding by taking pressure off levees.

But since then, the spillway has been the subject of decades of legal wrangling over property rights and ownership of rich oil and gas fields in the spillway’s footprint. As a flood control device the spillway has been largely irrelevant due to its location downriver from New Orleans and because other spillways were built upriver from New Orleans after the Great Mississippi Flood of 1927.