JACKSON, Miss. — An environmental organization identified a tributary of the Mississippi River on Tuesday as the nation’s most endangered river of 2018 after a retiring senator revived a decades-old flood drainage plan.

A U.S. Army Corps of Engineers plan to curb flooding in Mississippi’s delta region threatens the Big Sunflower River and 200,000 acres (80,938 hectares) of surrounding wetlands, American Rivers said.

The project was pushed for years by U.S. Sen. Thad Cochran, a Mississippi Republican who retired this month. The project was thought to be dead after the Environmental Protection Agency vetoed it in 2008, citing the Clean Water Act.

But recently surfaced bill language authorizing the project has jarred environmental conservation groups awake, reinvigorating their efforts to end it once and for all.

Currently, when spring floods swell the Mississippi River, a floodgate is raised to keep that water from backing into the Big Sunflower. But when rainfall is heavy in the Delta as well, the Big Sunflower also floods, and the gate keeps that water from draining into the Mississippi, swamping the low-lying Yazoo Backwater and potentially wiping out crops.

The region most often flooded by the Big Sunflower is dominated by large row-crop operations, properties averaging 1,000 acres (404 hectares) of farmland. The Delta Council, a regional agricultural lobbying group, has pushed heavily for the project to defend these properties from damaging floods.

But environmental groups say the project it would drain over 200,000 acres (80,938 hectares) of surrounding wetlands that are home to a unique ecosystem and an array of wildlife. American Rivers also claims the floodwaters would be redirected away from large agribusinesses so that it damages less prosperous communities downstream instead.

Cochran, a senator known for bringing federal relief dollars to Mississippi, worked closely with the Council throughout his 40 years in the Senate. He pushed for decades not only to get the project completed, but to fund it with federal dollars, at an estimated cost of $300 million.

Prior to his retirement, Cochran made one final push as chairman of the Senate Appropriations Committee, inserting language into the Senate’s 2018 Omnibus bill ordering the project to be built “immediately and without delay or administrative or judicial review.”

That rider language was eventually dropped, but environmental advocates fear Washington staffers will insert similar language in upcoming bills.

The project would involve a system of pumps to control the water level of the Big Sunflower River. A Corps-designed system first authorized in 1941 would pump river water over the floodgate, back into the Mississippi when the Big Sunflower reaches 87 feet (26 meters).

A spokesman for Cochran said the project would protect Mississippians in six counties and would “save taxpayers in the long run.”

“Flood control is costly, but it’s not as expensive as floods and the damage they cause,” spokesman Chris Gallegos said in an email to The Associated Press.

____

Follow Sarah Mearhoff at: https://twitter.com/sarah_mearhoff . Read her work at https://www.apnews.com/search/Sarah%20Mearhoff .