Computation of Long-Term Three-Dimensional Hydrodynamics of New York Bight

A time-varying three-dimensional (3D) numerical hydrodynamic model has been applied to the New York Bight to provide flow fields to a 3D water quality model. The spatial computational domain extends from Cape May, New Jersey at its south-west end and Narragansett Bay, Rhode Island, at the north-east end and seaward to the shelf-break. As illustrated below, the numerical model has more than 2500 active horizontal cells and ten vertical layers. Features of the hydrodynamic model include coupling of temperature grids to better represent geometric features, and an algebraic vertical turbulence model based upon the assumption that turbulence production and dissipation are in equilibrium. Using historical forcing data, flow fields for the period of September 1975 - October 1976 have been computed. These results demonstrate that the numerical model is able to accurately reproduce the observed salinity field

Long-term beach response to groin shortening, Westhampton Beach, Long Island, New York

The groin field built at Westhampton, Long Island, NY, in the 1960s and early 1970s has functioned as intended in protecting a once-vulnerable 4.8-km long segment of barrier beach that had experienced repeated breaching. In 1996-1997, a tapered groin transition to the west was created. The tapering included placement of fill in the existing groin compartments and on the adjacent beach. The combined groin tapering and beach fill have been successful, and the renourishment interval for the beach to the west of the groin field has been extended. As a result, concepts have been put forward regarding shortening of all the original groins. The objective of the present study was to evaluate options involving groin shortening to supply the down-drift beach. The study evaluated not only the evolution of the shoreline, but also the beach and dune interaction for decade-long simulations that include storms

Effects of full-scale beach renovation on fecal indicator levels in shoreline sand and water

Recolonization of enterococci, at a non-point source beach known to contain high background levels of bacteria, was studied after a full-scale beach renovation project. The renovation involved importation of new exogenous sand, in addition to infrastructure improvements. The study's objectives were to document changes in sand and water quality and to evaluate the relative contribution of different renovation activities towards these changes. These objectives were addressed: by measuring enterococci levels in the sand and fecal indicator bacteria levels (enterococci and fecal coliform) in the water, by documenting sediment characteristics (mineralogy and biofilm levels), and by estimating changes in observable enterococci loads. Analysis of enterococci levels on surface sand and within sediment depth cores were significantly higher prior to beach renovation (6.3 to 72 CFU/g for each sampling day) when compared to levels during and after beach renovation (0.8 CFU/g to 12 CFU/g) (p<0.01). During the renovation process, sand enterococci levels were frequently below detection limits (<0.1 CFU/g). For water, exceedances in the regulatory thresholds that would trigger a beach advisory decreased by 40% for enterococci and by 90% for fecal coliform. Factors that did not change significantly between pre- and post- renovation included the enterococci loads from animals (approx. 3 × 10(11) CFU per month). Factors that were observed to change between pre- and post- renovation activities included: the composition of the beach sand (64% versus 98% quartz, and a significant decrease in biofilm levels) and loads from direct stormwater inputs (reduction of 3 × 10(11) CFU per month). Overall, this study supports that beach renovation activities contributed to improved sand and water quality resulting in a 50% decrease of observable enterococci loads due to upgrades to the stormwater infrastructure. Of interest was that the change in the sand mineralogy also coincided with changes in biofilm levels. More work is needed to evaluate the relationships between beach sand mineralogy, biofilm characteristics, and the retention of fecal indicator bacteria in sand