One of the central strategies for sustaining Louisiana’s coast has become the focus of some debate: freshwater diversion.

At an estimated price tag of more than $4 billion, the debate is more than academic. Plans developed by the Coastal Protection and Restoration Authority would deliver large amounts of Mississippi River water and sediments to restore coastal wetlands.

Two questions have been raised: whether freshwater actually erodes the stability of coastal marshes, and whether rising sea levels and a shrinking soil base might make the projects moot.

In both cases, scientists testifying before the authority argued that the diversions would build more land in the fast-eroding coast, as much as 300 square miles by 2060. That is a significant part of the giant $50 billion set of projects that is intended to stabilize and restore the coast over the next 50 years.

Diversion of river sediments is intended to mimic the natural process of the river building land. That process was interrupted by levees built in the last century.

“We’re moving forward with the master plan,” coastal authority head Garrett Graves told The Times-Picayune. “We’re moving forward with designing four of the largest diversions. And we’re building them.”

The recent disputes over diversion projects reflect the great diversity of interests in Louisiana’s coastal wetlands. Oyster growers and commercial fisheries owners fear the loss of saltwater wetlands.

Louisiana’s immense problem is also the nation’s immense task, as the state will never be able to accomplish all of the coastal projects without federal help.