Beach Erosion

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Beach sand and moving water are a very unstable, dynamic combination.Most children who have spent time playing at the beach learn this. Their carefully constructed castles, despite elaborate systems of protective moats and sand walls, won’t survive a single day.

I thought Hurricane Sandy might serve as a reminder that the shoreline is constantly changing and we need to be much more careful about building there. Instead, it seems that many people see that unfortunate event as an aberration. There is a push to rebuild damaged structures and fortify our beaches as if we can somehow keep them in one place.

We are now considering a sand-covered seawall to protect a string of motels that are now sitting on the ocean beach. They were not originally built on the beach. Some probably date to the 1960s, and would have been tucked behind the primary dune. Where is the protective dune today? If you draw a line between the dune to the east and the one to the west, the primary dune in that stretch of beach would be under the motels.

It seems clear that a surprising number of people have learned nothing and are in denial as to what is actually happening in the real world. Sandy has given rise to a battle cry that we can pull together and defeat Nature.

Sea level rise and shoreline erosion are viewed by some as fabrications of environmentalists. We can reign in our misbehaving beaches with a well thought out plan and the help of the Army Corps of Engineers. I’ve even heard one of our town board members ask the rhetorical question: Has the Army Corps of Engineers ever done anything wrong?

Longtime weather observer Richard G. Hendrickson, a keen student of local history, storms and beach dynamics, has a different take. In his book, “Winds of the Fish’s Tail,” in text and photographs, he documents changes in the location of our ocean beach, the negative impacts of shoreline hardening structures on the beach, and the perils of building on the ocean dunes.

Hendrickson also notes that our ocean shoreline has been receding for many years; it is not a recent phenomenon. In fact, our bay and ocean shorelines have been receding for thousands of years. In his book “Eastern Long Island Field Geology with Field Trips,” coastal geologist Les Sirkin describes the landward movement of the south shore beaches as a process that has been going on since the glacial ice sheet that formed Long Island receded some 10,000 years ago and the ocean was 300 feet lower and the beach was some 70 miles further offshore than it is today.

Changes in sea level have been measured in this area since tidal gauges were installed in 1890. The general trend has been upwards, with the only significant change since 1890 being the rate of rise. Over the 100-year period from 1890-1990, sea level rose approximately one foot in height. Because of Long Island’s generally low topography and sandy, easily eroded soils, this one-foot rise in sea level corresponded to a 100-200 foot landward shift in the shoreline.

This landward shift in the shoreline also took place along the tall bluffs at Montauk. Although only an estimated 7 percent of the bluff is composed of sand material, it had eroded approximately 100 feet between 1838 and 1956. The bluff on which the Montauk lighthouse is perched is now 225 feet closer to the ocean than it was when it was built in 1796. The site for the lighthouse was chosen to last 200 years; 217 years later it sits 75 feet from the surf. In the book “Living With Long Island’s South Shore,” the authors point out, “It is interesting that the early Americans exhibited a degree of prudence in their site selection that has been lost in our current desire for an unobstructed view of the sea.”

Ironically, this historic fact seems to have been overlooked by those who have successfully lobbied the Army Corps of Engineers to armor the lighthouse bluff and protect the historically significant landmark from the advance of the ocean. The huge rocks that were brought in have slowed the loss of the bluff face. But the big rocks sit on sand, in the water; they are no match for the surf. What would George Washington have to say about that? If he were around, I think he would give the order: “Retreat!”

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