DESIGN, CONSTRUCTION, AND MONITORING OF NODAL POINT EROSION CONTROL AT PLUMB BEACH, BROOKLYN, NEW YORK

摘要

Plumb Beach is located along the southern margin of Brooklyn, City of New York. The site is a low-lying, crescent-shaped and undeveloped barrier beach which extends approximately 5,000 ft from Knapp Street at the entrance of Sheepshead Bay channel east to the tip of tidal flat (Figure 1). There have been no beachfill activities in the project area since the 1992 emergency operation. The shoreline located to the west of the comfort station consistently retreated since 1992. As a result of the combined effects of the November 2009 and March 2010 northeasters, storm wave damage has encroached upon the bike path and endangering the Belt Parkway. The majority of eroded sediment material moved east and shoaled up the existing adjacent tidal marsh, impeding its normal tidal circulation. Some of the eroded material moved back into surrounding navigation channels, requiring more frequent sediment maintenance. A regional sediment budget shown in the USACE 1994 Reconnaissance Report indicated that a nodal point exists at the middle of shoreline, with sediment moving to the east, west and offshore, resulting critical erosion at the center of shoreline which requires frequent repair. A regional sediment containment system composed of two terminal groins and one offshore breakwater was proposed to contain the beachfill and to recycle the material accumulated updrift of the groins. This system was designed and built in the period from 2012 to 2014 in two stages. Monitoring of the system was conducted in July 2014 with satisfactory results.