Viewpoint

By Jim Marquardt

A south shore beach on the other end of Long Island kept me in pocket money for many years. I carried heavy, wood-framed beach chairs for summer visitors, and, finally, while in college, I roasted on a lifeguard stand.

Recently, I came across a book titled “Waves and Beaches: The Powerful Dynamics of Sea and Coast,” by Willard Bascom and Kim McCoy, and I decided I was long overdue learning more about the world that provided me with early income and enjoyment.

Waves and beaches are why you are here on the East End, even if you never put your toes in the sand.

Would the Hamptons be the Hamptons without its beaches? Even if you only dabble in a pool, think about the Hamptons beaches. Beautiful beaches brought the city folk out here many years ago. They wanted to get away from the steamy city, and enjoy breezes from the ocean.

It all started 21,000 years ago, when the great glaciers crept here from the mainland, pushing boulders and soil ahead of them. After the glaciers retreated, waves driven by wind, earthquakes, and the moon and sun tumbled and ground cliffs and boulders into sand. Wave action and tides ground granite rock into white sand of feldspar and quartz.

We can think of beaches as small, closed systems in which sand moves onshore or offshore at the whim of waves. Coastal currents sweep sand along the shore. Where the shoreline is straight, sand can be transported considerable distances. When the land ends, the water deepens and the current is reduced in velocity, so that the sand it has been carrying drops to the bottom.

The outermost ends surrounded by water are called spits. They form wherever there is a supply of sand, a transporting current and a dumping ground. Rockaway Point, or spit (what we called the “Irish Riviera”), northeast of the New York Harbor entrance, was built with sand from the Long Island coast and grew at a rate of 200 feet a year, until a series of groins and jetties stopped the advance.

Herein lies the problem for our beaches. These rivers of sand flowing along the coast come from the erosion of valuable property. And the sand is often deposited where it is not wanted — another problem.

Waves create two major beach forms, berms and bars. Berms are flat and above water, producing the familiar part of the beach where you plant your beach chairs and blankets. Bars are underwater ridges that parallel the shore.

The two forms exchange sand over the year, performing on a moving “dance floor” propelled by wind, tide and climate. Wave size depends on wind velocity and duration, and the extent of water open to the waves, known as fetch. (During World War II, Scripps Institution of Oceanography predicted the waves and surf that would be expected on an enemy-held beach during amphibious landings.)

Sandy beaches compose over 30 percent of the world’s ice-free shorelines. Beaches are ever-changing, restless armies of sand particles, always on the move. Short-term changes are usually imperceptible, but in a week or so, you might see a small vertical cliff cut into the berm, or a newly added ridge of sand along the beach face.

You might also see waves breaking on offshore bars. Wherever there are waves, there is constant shifting, constant readjustment. When the waves are small, the sand on the bottom moves shoreward in an orbital motion. Although the orbiting water retreats seaward an equal distance, the sand is likely to be dragged along the bottom and doesn’t return quite as far. Consequently, the motion of sand is landward when wave steepness is small.

But when large waves follow one another closely, there is turbulence in the surf zone, keeping the sand in suspension as the waves rush up the beach; the leading edge deposits sand atop the berm, raising its height. Steep winter surf can build the berm higher while cutting back its front, adding sand to bars from erosion of the berm.

Wet sand contains minute animals that live between the sand grains in a film of water. A flock of sanderlings scurrying along at the edge of the waves is a sure sign that some of these creatures are there to eat.

Waves normally break at a slight angle to the shore, creating a current that moves water and sand along the beach. Structures meant to keep the beach from eroding will reduce wave action and turbulence, and the sand will settle out. But where one part of the shore is protected, another part must supply the sand.

Because they are expensive and not a long-term solution, groins are no longer preferred for maintaining a beach. Instead, simple beach nourishment means trucking in sand from a different location. Another common method dredges sand offshore and pumps it onto the beach.

Sand dunes are a familiar coastal defense, acting as a sort of dike to prevent flooding of inhabited areas by unusual high tides or waves. Dunes naturally develop when the wind blows dry sand into beachgrass on the back of the beach. Wind speed is slowed by the plants, and sand is deposited around them.

Slatted fences are often used for the same purpose. In fact, Gary Goleski, superintendent of the Department of Public Works for the Village of Southampton, said that they install such fences to reinforce dunes at the entrances to beaches. Otherwise, our local beaches seem to take care of themselves, even in the violent Superstorm Sandy, which devastated parts of Long Island.

A powerful storm can open up channels in the barrier beach. Most close naturally, but the Shinnecock Inlet that connects the bay to the ocean has remained open, and large stone slabs now line the sides of the channel to prevent erosion. Marine algae such as sea lettuce, rockweed and Irish moss usually grow on these stone jetties.

Another example of moving sand is the Cedar Island Lighthouse, which stood on a 3-acre island to guide whale ships into Sag Harbor in the 1800s. The famous 1938 hurricane created a sandbar that connected the island to East Hampton, where it now is part of Cedar Point Park.

Fortunately our South Fork beaches seem reasonably stable, but we shouldn’t be too confident. A recent article in The New York Times describes the devastation taking place on the New Jersey Shore. Despite millions of dollars spent over the years on remediation and barriers, beaches are eroding and shorefront homes are being built high on pilings to avoid flooding.

And, of course, with the effects of global warming evident throughout the world, all predictions about beaches and shorefronts are up for review.

Jim Marquardt, a resident of Sag Harbor, writes the “Looking Back” column for The Sag Harbor Express.