SPATIAL AND TEMPORAL METRICS OF SEDIMENT MOBILITY AT PLUMB BEACH, NEW YORK CITY, 2012-2015

Plumb Beach is a spit located within Jamaica Bay in Brooklyn, New York, fronting the highly-travelled Belt Parkway. Due to its close proximity to the highway infrastructure and role as a buffer from storm impacts, the erosional and depositional trends of the area are of high interest to a variety of stakeholders, including the National Park Service and the City of New York. From 2008 to 2012, a sediment budget analysis showed a net loss of volume in the western and central portions of Plumb Beach on the order of -5,000 m³/y (in the area closest to the Belt Parkway) and a net gain in volume in the far eastern portion of the beach on the order of +500 m³/yr.

Just before Hurricane Sandy, 97,100 m³ of sediment was placed at Plumb Beach to buffer the erosion problem in the central area of the beach. In addition, the Army Corps of Engineers constructed 2 groins and a breakwater in the summer of 2013 in an effort to stabilize the beach. The fill and recently installed structures comprise a framework for the continued topographic evolution of this site.

Using highly accurate topographic data from geodetic GPS surveys, the magnitudes of change of the beach-dune system at Plumb Beach are examined on a 3-dimensional basis as an update to the previous sediment budget analysis. Analysis of digital terrain models develops volumetric calculations of the coastal topography and lead to the construction of a sediment budget for alongshore compartments. Spatial and temporal variations of the compartments give a complete view of the erosional and depositional trends and gradients along portions of Plumb Beach as well as the entire area of study. Analyses of the collected data sets reveal the overall effect of the newly-constructed structures on the sediment pathways at Plumb Beach.