Building on sand: The effort to protect Long Island's communities, beaches

Picture a washing machine. Now imagine nearly 50 million of them lining the 6.5-mile strip of white sand at Wantagh’s Jones Beach State Park, located just 35 miles east of Manhattan on a barrier island in the Great South Bay claimed by both Nassau and Suffolk counties.

Henry J. Bokuniewicz, distinguished service professor at Stony Brook University’s School of Marine and Atmospheric Sciences, estimated that’s how much sand — 25 million cubic yards — Jones Beach has had poured on it since the 1950s.

That is the equivalent of all those washing machines, as two of them equal about one cubic yard. All of that sand has been placed on Jones Beach — much of it dredged at great expense from Fire Island Inlet — to keep the channel open for boaters and to combat nature’s relentless erosion.

Both scientists and longtime beachgoers agree on at least one point: The millions of cubic yards of sand poured on South Shore barrier islands over the years have traveled in unexpected ways.

Jones Beach and its eastern cousin, Babylon's Robert Moses State Park, for example, each have narrowed in the east and fattened in the west.

The impetus for the continuing infusion of sand — and indeed an effect of it — is the desire to protect the still-growing, low-lying bay communities and Fire Island, a beloved summer resort just 65 miles from New York City on a barrier island that overlaps the eastern end of Jones Beach Island.

The U.S. Army Corps of Engineers has proposed a $1.2-billion plan for Suffolk’s 83-mile long southern coast that includes building dunes on Fire Island and marshes in the bays. The Fire Island to Montauk Point plan, yet to be finalized, also would raise or flood-proof 4,400 at-risk homes. On an annual basis, FIMP would cost just over $67 million — and save nearly $73 million by reducing storm damage, the Army Corps says.

Critics, however, say the Army Corps overstated the plan’s benefits by inflating the likely flooding caused by breaches on Fire Island. Navigational inlets pose a far graver threat, they say, but closing them with surge barriers would cost billions of dollars and trap pollution in the Great South Bay — and possibly flood areas outside the gates.

Fears that the one breach superstorm Sandy cut through Fire Island in 2012 that was left open would increase flooding in the bay were not borne out, scientists say. Instead the breach at Old Inlet, expected to close on its own though the experts cannot say when, cleansed pollution in that area, delighting fishermen.

As a temporary measure, the Army Corps has spent at least $207 million building table-height dunes with nearly 7 million cubic yards of sand on the one-third of the 32-mile long Fire Island that is dominated by summer homes — but not in the national park. 

That sand, the Army Corps says, will have to be replenished every four years over the next 30 years, at an estimated cost of $525 million to state and federal taxpayers.

As this and similar projects make clear: South Shore beaches, since the last century, have received much more sand than the Netherlands a few years ago used for its Sand Motor, or Sand Engine. For that anti-flood project, about 28 million cubic yards of sand were scooped out of the North Sea, forming a new approximately $81-million peninsula. The ocean is expected to relocate that sand along six miles or so of coast to protect the mainland without dictating where the sand migrates.

Back on Long Island, the results of about a century of dredging, dune building and installing groins and jetties on the South Shore reveal how complicated and perhaps impossible it is to predict the outcome of projects that look certain to work on paper — until they are built and subjected to powerful winds, tides and storms, scientists say. And these experiences suggest proceeding with caution, they say.

In the past two decades, Robert Moses State Park has received about 3.5 million cubic yards of sand, Bokuniewicz estimated.

His calculations are in addition to the 40 million cubic yards of sand that built the 1929 Jones Beach State Park and the parkways in the early years of their development.

How much sand was poured onto Long Island’s first state park, the 1924 Fire Island State Park, after the deadly 1938 hurricane called the Long Island Express, apparently was not recorded. Histories only say it was enough to raise the elevation of the park that lies east and south of Jones Beach and was named after master planner Robert Moses in 1964, to 18 feet above the mean sea level.

Fire Island National Seashore, the national park east of Robert Moses State Park on the barrier island it shares, also was created in 1964.

The wind and waves, hitting the South Shore at an angle, carry sand from the east to the west, and, geologists say, likely on toward the New York Harbor, where the tides push it out to sea — or possibly even south to Sandy Hook, New Jersey.

“What jumps out geologically is ‘Wow, that is a lot of sand in the system, when you see that westward migration,” said Erika Lentz, a U.S. Geological Survey research geologist at Massachusetts’ Woods Hole Coastal and Marine Science Center.

While beaches tend to gain sand in summer, when winds and waves are calmer, powerful winter storms accelerate the westward flow, which for Long Island starts out around Montauk, at the easternmost end of Long Island.

“That bluff is eroding, and that liberates sand to feed the beach,” Lentz said.

Sandbars and underwater glacial deposits add to the Island’s supply, geologists say. “Every time a wave comes onto the beach and crashes, it picks up grains of sand, and then pushes them back out,” said Christopher Hein, assistant professor at the Virginia Institute of Marine Sciences in Gloucester Point.

Swimmers here are familiar with the waves’ westward push.

“It’s the same thing; on Robert Moses: When you leave your towel, you go out, you’re playing in the water, and when you come back, you notice your towel is up the beach from you,” said Hein, a Commack native. “That is the process of ‘longshore transport.’ ”

No one quite knows what the South Shore would look like had engineers not tried to anchor the beaches in place.

“It’s difficult to untangle the human influence today from what would naturally be happening,” Hein said.

How different projects — groins, jetties, bulkheads and dunes — affect one another often is not fully grasped.

“These features are intended to serve the area they are directly adjacent to, but that’s part of what makes coastal management so difficult. It’s part of this large, dynamic system in which doing something somewhere also affects your neighbor,” Lentz said.

However, the way Long Island’s barrier islands have shape-shifted over nearly two centuries can be readily studied because the New York Harbor area is where the first federal surveyors set to work in the 1830s.

“Those are very detailed and accurate shorelines,” Lentz said, explaining the maps’ value led the USGS to digitize them despite the effort and expense.

Consider Bay Shore's Captree State Park, partly located on the eastern end of Jones Beach Island. 

“You can see that in the 1830s maps, Captree used to be a barrier island,” said Hein. “Jones Beach Island used to be exposed to the main ocean; Robert Moses has gotten longer and extended.”

Geologists agree that building the jetty at Fire Island’s Inlet in 1941 halted the island’s westward expansion that — at a rate of about 200 feet a year — added six miles to its length, when measured from the original 1826 lighthouse that once stood next to it.

Without the jetty, Michael S. Fenster, director of environmental studies at Randolph-Macon College in Ashland, Virginia, said: “It looks like, if nature were left to run its course, the end of Robert Moses beach — that’s Fire Island — it looks like it would connect to Jones Beach.”

In 1959, the 875-yard-long sand dike called Sore Thumb was built on Jones Beach Island, extending south into the bay, between Oak and Cedar beaches. While it helped reduce some erosion on Jones Beach Island and block the inlet from moving north, geologists say, the inlet remains a star sand trap.

For decades, tens of millions of dollars have been spent pumping its sand back to the beaches. “It’s kind of stuck in this cycle,” Lentz said.

Last year, for example, the Army Corps said it spent $26 million pumping out 2.1 million cubic years of sand. Much of that sand was destined — yet again — for Babylon’s Gilgo State Park, about 10 miles east of Jones Beach.

Gilgo, popular with the surfing and fishing crowd, was closed because of severe erosion in 2016. That was only three years after the ocean reclaimed the sand from a $15 million dredging project focused on the state park. 

Ultimately, scientists say, the vast amounts of sand placed on the South Shore beaches obscures any analysis of its impact.

“Beaches are dynamic,” said Courtney Melrose, a geologist who works at Garvies Point Museum & Preserve in Glen Cove. “If you have something artificially made bigger, nature over time is going to make an impact, making it bigger or smaller, depending on the erosional process that is happening to it.”

Consider the varying ways Robert Moses State Park has responded. From 1960 to 2000, its eastern beach widened just 11 yards, according to the latest USGS comparative data. The western beach, however, grew much farther into the sea: about 219 yards.

Jones Beach State Park, over the much longer period from 1830 to 2000, appears to have widened more evenly. Both its eastern and western ends expanded into the Atlantic by about the same 219 yards, the USGS maps show.

Yet, a shorter time frame paints a starkly different picture, likely revealing Fire Island Inlet jetty’s impact. From 1947 to 2000, the east end of Jones Beach State Park narrowed by 88 yards, the maps show.

“Sand that would have been feeding Jones Beach before 1947 now is being caught by the jetty; to a certain extent that might be exacerbating the 80 meters of erosion,” said Lentz, using the metric equivalent of 88 yards.

“It appears to be a more localized issue, which is why you have some accretion downdrift,” she added. Downdrift is the net longshore transport of sand. In 1975, Field 9, the park’s easternmost lot, was closed because of erosion. Nearby Field 6 now is often the most popular spot to park as the walk to the sea is much shorter than from western lots.

During the same 1947-2000 period, the western end of Jones Beach widened by 252 yards, the maps show.

The jetty also appears to be accelerating Gilgo’s erosion in the east.

“Democrat Point, that little point of land on the westernmost tip of Robert Moses, that sand should be moving over … to the Gilgo area and to Jones Beach,” Hein said.

“It should be going across the inlet. It’s not; it’s stopping,” he said.

For decades, scientists have studied the role of Long Island’s barrier islands and how to preserve them, from continuing to spend countless millions of dollars dredging inlets and replacing sand on beaches to spending much more installing enormously expensive floodgates at Fire Island Inlet in the west and Moriches Inlet in the east.

A novel approach, explored by Army Corps experts Nicholas C. Kraus and John F. Tavolaro, who joined Florida Tech professor Gary. A. Zarillo in a 2003 report, is moving the Fire Island Inlet back to its 19th century location, six miles east.

Returning the inlet to its original site by digging a new channel in the barrier island would boost the flow of water in and out of the Great South Bay and increase sand shoals in the inlet, the report said. Abandoning the current inlet would free sand to flow to western beaches, such as Gilgo, for half a century to a century, the report said. Oak Beach would be shielded, and the relocated jetty “would impound sediment, gradually building the width of the fragile beaches of Fire Island located to the east,” the report said, though it added further study of “potentially unacceptable negative consequences” — such as the risk of higher storm surges — needs to be analyzed.

Geologists say that over the next decades society likely will have to decide whether, how and at what potentially astronomical cost coastal areas should be shielded as the climate warms, storms intensify and the seas rise. Whether or how long federal taxpayers will continue to pay for the protections needed so that people can live by the water — either in vacation or permanent homes — is unknown. Some scientists say that in the future society likely will only be able to shield urban areas, such as Coney Island, or New York City's major airports.

“People really are the wild card when it comes to coastal management,” Lentz said.

For now, the Fire Island jetty is preventing sand from growing the island to the west.

“Regarding how far west Fire Island can grow: probably not too much farther than it is now since maintenance of the inlet channel will almost certainly prevent the island from growing much more, even though there is clearly net east-to-west longshore sediment transport,” Andy Coburn, associate director, Program for the Study of Developed Shorelines at Western Carolina University, said by email.

Over time, however, the jetty’s impact has lessened. Coburn said: “Although the jetty has clearly slowed expansion of the island to the west, it doesn’t look like it has much sediment trapping ability left since there isn’t much of the jetty sticking out at the ocean end, and sand seems to be getting around it.”

If dredging were stopped at the Fire Island Inlet, the barrier island likely would resume growing west, geologists say, though any extra shelter for the mainland could be limited.

“Considering the eastern end of Jones Beach Island is north of the west end of Fire Island, I don’t see how any extension of Fire Island will provide any additional degree of protection to the mainland,” Coburn said.