East Lyme — The state and federal governments are spending a combined $582,000 to save the marsh at Rocky Neck State Park from drowning.

The U.S. Fish and Wildlife Service last week announced it will pay $341,500 to restore the degraded salt marsh. The state Department of Energy and Environmental Protection will provide $240,474.

Min T. Huang, DEEP migratory bird program leader, said the effort addresses increasing sea levels by dredging a portion of the brook and using the sand to build back the marsh in ways that promote fish passage and help water circulate as it should.

The marsh sits on the opposite side of the train tracks from the Long Island Sound within the state park. Huang said it's connected to the Sound by a culvert system that runs underneath the trestle, restricting the flow of water between the relatively wide brook and the narrow outlet.

"As the tide goes out, not all the water leaves the marsh," Huang said. "As that occurs over time, the water table rises and the marsh slowly drowns."

He also attributed the inundation to increasing storms.

"If you look at aerial photos of the last century, you can see how the marsh itself is disappearing and basically what you're getting is this huge expanse of just open water and muck," he said.

Bride Brook was also the site of a large-scale environmental project in 2010. That's when the two culverts were replaced to clear the way for river herring, known as alewife, in what is known as one of the largest migratory runs in the state.

Curt Johnson, president of the environmental nonprofit organization Save the Sound, said placing the dredged material back on the marsh surface is vital to maintaining an ecosystem that fosters wildlife and protects the shoreline from flooding. He said material dredged from marshes in Connecticut has been viewed until recently as a waste product to be dumped in Long Island Sound.

Describing his organization as supportive of the marsh project, Johnson pointed to similar dredging and depositing methods that are being used more often in the southern United States and places as close as Rhode Island, New York and New Jersey. He credited the practice — known as thin layer deposition — with helping to restore the islands of Jamaica Bay near John F. Kennedy Airport in New York City in a project carried out between 2004 and 2014.

"It's amazing," he said. "Within a year or so of bringing that sediment up and planting a little bit of saltmarsh grass, these islands are thriving."

Thin layer deposition must be carried out "on a very large scale" if marshes are going to survive, according to the environmentalist.

U.S. Rep. Joe Courtney, D-2nd District, emphasized the project is one of 25 in 13 states that were awarded a total of $20 million by the U.S. Fish and Wildlife Service to restore coastal wetlands and mitigate the effects of climate change.

"Salt marshes are home to an incredibly diverse range of wildlife, from birds to blue crabs, and they're extremely important for our region's fish population," Courtney said in a news release. "If that wasn't enough, healthy salt marshes also help mitigate the impacts of flooding on coastal communities by absorbing storm surge."

According to an article in a student-run review put out by the Yale School of the Environment, wetlands keep up with rising sea levels through plants that trap sediment as a way to naturally increase surface elevations in the wetlands. But when sea levels rise at a higher rate, they "drown" the wetlands. And while marshes have the ability over time to retreat to higher elevations, that's not possible when the land surrounding it is already developed.

Johnson said the failure to use the marshes' own dredged materials to build them up again will result in the loss of the Long Island Sound's marsh system. That means the marshes won't be there to absorb storm surge before it gets to roadways, houses and businesses. It also means marshes will no longer serve as a home, breeding ground, nesting spot or stopover for a wide array of wildlife.

He pointed to the upgrading of municipal sewer treatment systems around the Long Island Sound, long a focus of his organization and others like it, as evidence that people are willing to invest in solutions to big environmental problems.

"The cost of attacking this problem around Long Island Sound is a fraction of the cost that we have borne to upgrade these sewage treatment systems," he said of communities in the region. "We have invested, between New York and Connecticut, about $4 (billion) to $4.5 billion over the last 25, 30 years — one treatment plant at a time."

According to Huang of DEEP, the overriding restriction preventing the flow of water in and out of Bride Brook is the railroad tracks over the culvert. But the only way to widen the span below would cause serious disruption to railroad service above, he said.

"That project, I doubt, would ever get done," he said of what he estimated would be a "multi, multi" million dollar effort.

According to Huang, DEEP still is in the process of securing the state and federal permits to start the restoration plan funded at just over a half-million dollars. He estimated the work could be completed by this time next year in the best-case scenario.

He said he does not anticipate any impact to the public, since the work will be confined to the marsh area not open to visitors.

e.regan@theday.com