Since the 1930s, Louisiana has lost more than 2,000 square miles of land, roughly the size of Delaware, to subsidence, sea level rise and the loss of sediment caused by construction of the levees along the length of the Mississippi. Those levees have reduced flooding and saved countless lives over the decades, but they have also penned up the nourishing sediment that used to flow out with the spring floods and renew the Delta. That, and other damage to the wetlands that includes channels cut for oil and gas exploration, have led to ongoing losses of about a football field of land every 100 minutes.

In response, the state has developed a $50 billion, 50-year master plan for coastal restoration and protection. The first was published in 2007 and Louisiana has re-evaluated and upgraded its plans every five years since then.

Officials have developed an ambitious roster of projects to protect areas of the state and rebuild wetlands, which can buffer the effects of hurricanes. But planners have come to realize that they cannot restore all of the land lost over the decades, and have had to become strategic about what areas can be protected and how.

The Mid-Barataria diversion, and a similar structure farther north that will open eastward into another body of water, are among the most expensive, audacious — and promising — proposals. Land can be built through dredging and pumping sediment into place, and Louisiana has done some of that in some areas, including efforts to beef up the state’s barrier islands.

But that process is prohibitively expensive. The Mid-Barataria diversion could restore as much as 60 square miles over its first 50 years, the coastal authority says, building land in critical areas where people live, work and play.

The funding for the diversion comes from settlement money the state received from BP over the 2010 Deepwater Horizon spill.