Nature Notes: Fortify or Retreat?

We have lots of time to adjust to the changing sea level

It was the wise Greek Archimedes who in 250 B.C. formulated the principle of buoyancy and that a chunk of something that drops into the sea and floats displaces its own mass. If it sinks below the surface, it displaces its own volume. When a glacier slides off a mountain face into the ocean, it displaces its own mass, and the sea rises proportionately. As it slowly melts away and becomes one with the sea, the sea rises a bit more.

Archimedes didn’t discourse on the rise or the fall of the world oceans, but his principle explains that very phenomenon in progress today. It has been postulated that if all of the earth’s glaciers entered the oceans and melted away, the seas would rise as much as 250 feet. The complete melting of the Antarctic ice mass by itself would raise sea level as much as 200 feet.

What complicates the picture, something that Archimedes and the Golden Greeks never dreamed of, was the notion of the world’s floating landmasses, which move up and down according to the weight pressing upon them. Thus sea level will rise here and there relatively, depending upon the weight loss that will be experienced on a given tectonic plate. The last major glaciation in the Northern Hemisphere, which began to melt and retreat some 15,000 years or so ago, depressed the tectonic plates to a degree that sea level around our hemisphere was 300 to 400 feet lower than it is today, particularly so on both sides of the North Atlantic Ocean.

It’s scary, mind you, but it is becoming a reality, however slowly. Archimedes was a deep thinker and if he were alive today, he wouldn’t run around like a chicken with its head chopped off. Unless we human populations move inland and upland en masse and away from the coasts, that rise will eventually drown more than half of the world’s population if it continues on at an accelerated pace. Yet, such dire predictions are generations upon generations away. We have lots of time to adjust to the changing sea level.

Thus we should not panic. As long as humans have evolved and moved about on two feet, they have been in motion. First from Africa, then from Asia, and so on and so on. All matter is in motion, up or down, laterally, back and forth, and so are we.

Locally, perhaps, the best example of such a conundrum is the question of whether to fortify and remain or pack up and retreat. Take the Montauk Lighthouse. It is approximately 168 feet high (equivalent to a 16-story building) and was constructed from 1796 to 1797, making it one of the first major structures to be built in the United States. It was one of the first national public works projects in America and has stood on Turtle Hill for 230 years without flinching, overlooking the ocean and passing ships. It took a very long time to be recognized as a National Historic Landmark, in fact more than 225 years, thanks to the exhaustive work of the historian Robert Hefner, with the backing of the Montauk Historical Society, the lighthouse’s owner.

Many locals and outsiders wanted to move it to safer quarters, but the lighthouse people said no, a draft environmental impact statement decided in their favor and so today a great number of massive boulders, carefully placed to form a wave-resistant revetment, helps keep it where it is. Before that, a textile designer, Georgiana Reid, who had saved her Rocky Point home on a retreating bluff by creating a series of reed-filled parallel trenches, started working on the eroding lighthouse bluff on Earth Day of 1970 using the same technique. She patented it with the assistance of a young man from Montauk, Gregory Donahue, who not only learned the method, but learned it so well that he used it to save other Montauk landmarks, including a private residence known as the Stone house atop Montauk ocean bluffs west of Camp Hero.

The same Mr. Donahue, with backing from the Historical Society, and now New York State, will continue to fortify the lighthouse by reconstructing from time to time the rock revetment half-surrounding it in a never-ending process of refitting existing rocks and adding new ones. Such an instance of “fortify and remain” has been employed here and there successfully elsewhere in Montauk and on the South Fork in general. 

Southampton Town and the homeowners along the oceanfront in Sagaponack, Bridgehampton, and Water Mill used a different technique to fortify 

and remain. Under the direction of Southampton Town, a special erosion tax district was formed, the monies collected from which paid for a project involving the massive pumping of sand from offshore by a very large dredge onto the retreating beach. The special tax district is permanent and will provide the same relief in the future should the beach retreat to a thin strand as in the past.

Recently, a consultant studying East Hampton Town’s hamlets has put forth a plan to save downtown Montauk from ultimate destruction from flooding and waves by moving some development to higher ground, a plan that has been discussed in one form or another for years. Not only would such an undertaking take an immense amount of time, money, and effort, but the questions remain: Would there be enough safe land to relocate to, and how many more years would it be before those buildings would need to be moved again? The land to the east of South Essex Street is higher, but its shorefront bluffs and dunes are subject to the same erosive conditions as the downtown dunes.

The Netherlands, with much of its land below sea level, faced a similar fate at the hands of coastal storms years and years ago. Did it retreat? No, the government built a large earthen wall along its North Sea shore. Yes, it has to be maintained from year to year, but it’s working and the country has been prospering ever since. 

I am suggesting a much less expensive fix for downtown Montauk. Either form a special tax district along the Atlantic shore from Ditch Plain to west of Umbrella Beach, as then-supervisor Jay Schneiderman proposed in 2002, or build a rock revetment in front of the motels and condominiums, but not at the town’s expense. I would not count on the Army Corps of Engineers’ Fire Island to Montauk Point Reformulation Study for help; the federal government has been at it for 50 years with little in the way of real results. The feds have even recently admitted that the FIMP study, as it is known, will not provide much relief for Montauk.

So which is it, folks?: The very expensive move of Montauk up the hill to the east; having the motel and condominium owners build a substantial revetment in front of their facilities, or, not as expensive and more practical than the first, create a special taxing district to provide money to pay for regular deposits of sand nourishment?

Larry Penny can be reached via email at