As a Beach Erodes in the Hamptons, Community Tensions Swell A large rock sea wall was installed in front of the Montauk Shores Condominium complex on the eastern edge of Ditch Plains beach in Montauk, N.Y. MONTAUK, N.Y. - Perched at the edge of the Atlantic with cliff neighbors including Paul Simon and Dick Cavett, Montauk Shores shares a distinction with Bohemia Cove in Malibu - it is one of the most desirable trailer parks in the United States. Its stationary mobile homes have water views that are no less sweeping than those of Andy Warhol's former estate, Eothen, just a few miles to the east. The cost of that view is vulnerability. Hurricane Sandy breached the rocky dune barrier that had protected the park for years. So its managers built a mighty, new and bigger sea wall of large rocks that promises to fend off the next such super storm. But as is often the case along the fragile shore, what's good for one community may have unintended effects elsewhere. The wall is being identified as a possible culprit in the drastic erosion of sand at Ditch Plains, just to the west, a beach so renowned for its cliffs and surf that fashion and magazine photo shoots take place there with increasing regularity; an apparel company is even seeking to trademark its name. And so the trailer park - where mobile homes are sold as condominiums, priced as high as $650,000 - and its sea wall have found themselves at the center of a man-versus-nature dispute in this exposed Long Island hamlet on the ocean. The deterioration of Ditch Plains's beach and its possible causes have strained the cooperative abilities of the five-member board of the Town of East Hampton, which includes Montauk; partisan fault lines there already rival those of Washington (they are just more personal). It is only now, on the eve of the Fourth of July holiday week, that the town is moving forward with a temporary solution, spending approximately $85,000 to dump more than 4,000 cubic yards of sand on the beach. The town fully knows that much of the sand may eventually be be washed away. William J. Wilkinson, the town supervisor of East Hampton, called it "temporary relief to try to see if we can even have a beach this summer at Ditch." The idea that a barrier at the trailer park could have a negative effect at Ditch Plains was not new. East Hampton's own water revitalization plan of 1999 - which serves as a binding code - concluded that the trailer park's existing protective rocks "may influence erosion at Ditch Plains" and that more extensive work there could "aggravate this situation." After the storm, East Hampton officials did grant the park a permit to restore its dune "with sand and relocation of existing rocks," $2,000 worth of work all told. But the park trucked in large new rocks, building the wall so it appears to jut farther into the sea - covering a narrow beach that was once exposed at low tide - and higher into the air. Through the spring, the storm-ravaged beach at Ditch Plains stood like an open wound at the heart of the hamlet; once vast and sandy, it was worn down to dark and ugly hardpan - and at high tide parts disappeared entirely. Ditch Plains often suffers some erosion in the off-season from hurricanes and winter nor'easters; it is usually restored naturally by summer. But that did not happen this year. As Memorial Day approached and the town had to close the beach to bathing, tensions rose, and the search for reasons began. The major environmental group here, Concerned Citizens of Montauk - which often finds itself at odds with Mr. Wilkinson, a Republican and former Disney executive - identified one thing that existed near Ditch Plains now that did not exist before: the newly rebuilt sea wall at the trailer park. The group's executive director, Jeremy Samuelson, blamed the wall in a tense exchange with Mr. Wilkinson at a public meeting in May. Mr. Samuelsen cried out, in a mostly empty meeting room during a board discussion of the beach, that the rebuilding of the sea wall had devastated Ditch Plains. Mr. Wilkinson declared that, as far as he was concerned, the hurricane had been strong enough to cause such lasting damage and that the trailer park sea wall "had nothing to do with the scouring at that beach." This exchange ended in an accusation by Mr. Samuelsen that Mr. Wilkinson was in the pocket of major landowners and Mr. Wilkinson's dismissal of the accusations as "snotty commentary" from "Mr. Lobbyist."