Managing Sediment Budget: Applications and Opportunities, Gateway National Recreation Area, National Park Service

AcknowledgmentsThis research is supported by the Inventory and Monitoring Program of the Northeast Coastaland Barrier Network of the National Park Service. A number of people participated in the fielddata collection and data reduction. The involvement of Kathy Mellander, George Frame, PeterShipton, Patrick Kiprotich, Aaron Love, Peter Dennehy and Mario Resina are herebyacknowledged for their tireless efforts.

ReferencesBohlen WF 1990. An Examination of Factors Governing the Erosion of Plumb Beach, Brooklyn,New York. Dept. of Marine Sciences, unpublished report, Univ. of Connecticut, Avery Point, CT.

Psuty NP 2008. Plumb Beach: A problem of losses and gains of sediment. Unpublished report,Institute of Marine and Coastal Sciences, Rutgers University, Highlands, NJ.

Psuty NP, P Dennehy, T Silveira and N Apostolou 2010 Coastal geomorphology of the oceanshoreline, Gateway National Recreation Area: natural evolution and cultural modifications, asynthesis. Natural Resource Report NPS/NERO/NRR-2010/184. Fort Collins, Colorado.

Taney NE 1961. Geomorphology of the South Shore of Long Island, New York. Beach ErosionBoard, Technical Memorandum No. 128. U.S. Army Corps of Engineers, Fort Belvoir, VA.

US Army Corps of Engineers and Coastal Planning & Engineering, Inc. 1994. Jamaica Bay,Marine Park and Plumb Beach, New York, Combined Beach Erosion Control and HurricaneProtection Project: Reconnaissance Study. New York District, New York, NY.

ConclusionsEfforts to supplement the sediment supply of Plumb Beach and to maintain theshoreline position have been attempted several times. However, the conditions oferosion at the central portion of the barrier and transport to the distal margins continue.The erosional trend will persist because of the exposure to the incoming waves throughthe Rockaway inlet and the lack of sediment input. Any sediment placed in the center istransported largely to the east to augment the aggrading spit and spill over to thewetland. Sediment management is a major challenge to the several agencies withjurisdiction over Plumb Beach that, having different objectives, have to ameliorate theerosion at the central portion and reduce the sedimentation impacts on the marsh habitat.

IntroductionThe challenge of managing sediment input, transport, and subsequent output dominates coastal concerns within the several units of Gateway National Recreation Area (Fig. 1). Driven by a generally persistent direction of functional incident waves at the local level, evolution of the coastal geomorphology of the several units in Gateway NRA is constrained by the factors affecting input sediment supply to the unit boundary, to the transport mechanisms within the units, and to the elements of sediment manipulation at the unit terminus. Some portions of the units have a process-response relationship in a quasi-natural system without impediments to sediment transfers, whereas other portions have groins, jetties, and bulkheads that direct or limit dimensions of the geomorphological responses and resulting features.

Evolution of Plumb BeachPlumb Beach is a remnant of the eastern end of the Coney Island barrier island and itsassociated tidal inlet delta (Psuty et al. 2010). The Rockaway barrier island to the south extendedwesterly during the past several centuries (Taney 1961), eventually shielding Plumb Beach fromthe ocean waves direct action, and dredging of the channel into Sheepshead Bay severed thesediment transport vector toward the present position of Plumb Beach. Creation of the BeltParkway (late 1930s) promoted placement of fill on the wetlands and shoal inland of PlumbBeach and the establishment of a re-formed shoreline at the seaward margin of the fill. Thedredging of the navigation channel to the west of Plumb Beach resulted in the absence ofsediment input, and net erosion displaced the shoreline inland toward the Belt Parkway. Tocounter the erosion, several beach nourishment episodes have been carried out in the centralportion of Plumb Beach. Additionally, rip-rap material and offshore breakwaters and groins havebeen placed using old tires to intercept the incident waves and reduce the energy reaching thebeach (USACOE and CPE 1994). The most significant beach nourishment project was conductedin 1992, with the placement of 147,000 m3 of sand dredged from the Rockaway navigationchannel (Bohlen 1990; USACOE and CEP 1994; Psuty 2008). The existing coastal topography atPlumb Beach derives from the combination of episodes of emplacement of fill and theirsubsequent erosion and transport, which has widened and extended the central erosional zone tothe east and to the west.

Recent Shoreline ChangeThe central area of Plumb Beach is the locus of major erosion, about 1,900 m3 (2,500yrd3) annually (USACOE and CEP 1994). Exposure to waves entering throughRockaway Inlet is continuing to mobilize the sand in this central portion which ischaracterized by a narrow beach and low dune topography with a small escarpment(bluff) eroding back into the fill (PB2). Some of the sediment is transported into thenearshore in the form of low sand waves propagating alongshore to the east, adding tothe distal end of the spit-like beach-dune topography that is extending easterly (PB4and PB5). Severe erosion is damaging the local multi-use path in several locations andis threatening other aspects of the infrastructure, such as the Belt Parkway. Recentstorms (November 2009 and Marsh 2010) have destroyed portions of the multi-use pathand the erosion area has extended easterly, promoting cut-back and scarping of thedunes (PB3). Much of the recently-eroded sediment is transferred to the lower beachface inducing the seaward displacement of the shoreline, and is transported alongshorepromoting the enlargement of the sand spit that is encroaching over an importantfringing marsh habitat.

Jan 2007 Jun 2007 May 2008 Oct 2008 Mar 2009 Nov 2009 Mar 2010

Distance to belt Parkway

Scarped dunes (PB3)

Multi-use path (PB2)

Easterly extending spit (PB5)

Institute of Marine and Coastal Sciences, Rutgers, The State University of New Jersey

Plumb Beach

May-08 Sep-08 Apr-09 Oct-09 Nov-09 Mar-10

* Cross-section calculated for area above NAVD88

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