Nature Could Preclude Need For Flow Structures; Town Going Ahead With Permits For $3 Million Project

CHATHAM – Flow training structures to mitigate erosion and shoaling off Morris Island could cost as much as $3 million. But officials say they might not even be needed and that nature may take care of the problem on its own.

Given the dynamic nature of the town’s shoreline, however, there’s an equal chance that things could get worse.

The town is currently pursuing state environmental permits for the structures, a series of steel walls to be placed off Crescent Beach with the goal of slowing currents to stop erosion of the beach and sand from shoaling the Stage Harbor entrance channel. A $94,540 grant from the state Office of Coastal Zone Management’s Coastal Resilience Grant Program — the third the project has received — will cover the cost of completing the permitting.

The 2017 Fool’s Cut opened the area between Morris Island and North Monomoy Island to the Atlantic. Because the ocean’s tide level is higher than Nantucket Sound, the result was an almost constant east-to-west flow of currents, sweeping vast amounts of sand into the boating channel between the two islands and into the Stage Harbor entrance channel.

Constriction of the channel between the two islands also accelerated the current and caused significant erosion, as much as 20 feet per year, at Crescent Beach. The erosion has been focused on the spot where the Stage Harbor entrance channel was located before the Army Corps of Engineers closed the opening and created a new entrance channel about a half mile to the west in 1964.

The concept behind the 1,000-foot structure proposed to extend into the water from the beach is to slow the current, which will keep sand from shoaling the channel, Coastal Resources Director Ted Keon said during an Oct. 24 informational session.

“It is a complicated approach to this issue, it is a unique solution that will be probably the first one in Massachusetts if not much of the east coast,” Keon said.

Because of the east-west flow, the area functions almost like a river as opposed to the usual coastal tidal process, said John Ramsey of Sustainable Coastal Solutions, the town’s consultant on the project. The solution is “more akin to something you would see on the Mississippi River than on the open coast of Chatham.”

In the six years since the Fool’s Cut there has been significant erosion at the Morris Island headquarters of the Monomoy National Wildlife Refuge as well as farther west at Crescent Beach. Erosion has slowed at the latter spot, however, due to a shoal that’s built up just past the revetments along the Morris Island shore. If that shoal goes away and erosion accelerates, there could be a breach in the narrow section of Crescent Beach where the old inlet was located. That would open Stage Harbor proper to shoaling and more wave action.

If that happens, “you’re going to have two inlets to Stage Harbor and you’re going to have different shoaling issues altogether,” Ramsey said. “So that’s something we don’t want to get to.”

Time is another factor. Ramsey said that within 15 to 20 years, by 2040, Monomoy is expected to attach to Morris Island, as it has in the past. That will cut off the flow between the two islands completely and stop the shoaling and erosion, although it will create other problems.

“After that, all of you boaters, you guys are going to have to go back around Monomoy again rather than taking the shortcut” between Morris and Monomoy islands, Ramsey said. “But that’s the way the natural system’s going to do it.”

All of those factors will play into whether the flow structures are built, as will the continued need for dredging of the Stage Harbor channel, which costs the town about $500,000 annually.

“If we have to do that for 10 more years, that’s $5 million,” said select board member Jeff Dykens.

Early estimates of the cost of the flow structures hover between $2.5 and $3 million, said Keon. And although the structures are large — 11 steel vanes at 398 feet, plus a 610-foot groin, with the vanes extended three feet above the water at high tide — and “not the prettiest thing,” they are temporary and easily installed and removed by vibrating them into the sand, which is a key factor with regulators, he said. As much as nine acres of sand, about 84,000 cubic yards, also will be needed to restore Crescent Beach.

“This is not a small structure,” Keon said. “It’s easy to install, but it’s a lot of material and you still need a very qualified contractor to get out there.”

The area where the structures would be installed is outside of the boundaries of the refuge, “which makes our lives easier if we’re trying to permit something like this,” said Ramsey.

Permitting is expected to be completed some time next year. At that point, officials will assess whether the structures are still needed and if so when they should be installed.

“Whether we ever do it remains to be seen,” Keon said. “And that will be the result of a lot of discussion with the general public as well as our select board, to decide if we need to do it, has the issue gone away, or do we really need to do something, presumably this type of approach, to address what is impacting our navigation and has the potential to breach Crescent Beach, which would not be a very good scenario at all.”