Rising sea

DEEP: Connecticut coast is vulnerable

levels are putting the state’s marshes at risk, according to DEEP.

Old Lyme — With sea-level rise in Long Island Sound predicted to be as much as 6 feet by the end of this century, the remaining salt marshes on Connecticut’s coast are particularly vulnerable to disappearing completely unless steps are taken to preserve them.

David Kozak, senior coastal planner for the state Department of Energy and Environmental Protection, offered that message Tuesday to an audience of about 80 people at the Town Hall. Kozak’s talk was one of a series of environmental science lectures sponsored by the Connecticut Audubon Society’s Roger Tory Peterson Estuary Center.

“Our marshes are constantly trying to keep up with sea-level rise,” he said. “It’s this constant battle between the water and the land.”

Marshes, transitional landscapes that provide critical habitat and food supply for wildlife, also buffer shorelines against flooding and storm surge, he noted. But many marshes were filled or have been severely compromised by development, making it even more important to preserve those that remain, he said.

“They’ve been diked, they’ve been drained, they’ve been ditched and we have roads going through them,” Kozak said.

DEEP and other coastal planners, he said, are using the Sea Level Affecting Marshes Model, or SLAMM, to show how the sea-level rise will impact specific marshes and adjacent roads vulnerable to flooding. Using sea-level rise predictions, land surface elevations, tidal data and other variables, he said, the model shows how a marsh is likely to change and identifies where conservation resources can be used most effectively.

The Great Island marsh on the lower Connecticut River, for example, is now mainly a “high marsh” system flooded by high tides three to four times a month, but by 2085 will become mainly a “low marsh” system that floods twice a day. The model shows undeveloped property adjacent to the marsh that could be purchased to enable the marsh to “migrate” inland and preserve both the high and low marsh, he said.

Some communities in New Jersey and Rhode Island, he noted, are dumping dredge spoils or sand onto marshes to raise their elevation as a buffer against sea-level rise.

“But this is very expensive, about $1 million per acre,” he said.