Alan F. Blumberg

Estimating the Volume and Salt Fluxes Through the Arthur Kill and the Kill Van Kull

The hydrodynamic transport characteristics of the Kill van Kull and the Arthur Kill, which connects the New York Bay to the Raritan Bay, have been investigated by using a three-dimensional, time dependent hydrodynamic model, ECOM. The objective of this study is to determine volume and salt transport through the Kill van Kull and the Arthur Kill and to obtain a basic understanding of the physical factors driving the salt transport through these important water bodies. The current model is an enhanced version of the original System Wide Eutrophication Model (Blumberg et al., 1999), which has been re-calibrated and re-validated in the New Jersey tributaries including the Hackensack, the Passaic and the Raritan Rivers. Volume and salt fluxes were determined by the decomposed correlation terms using the model computed salinity, temperature and currents. Results indicate that the net long-tem volume and salt flux is directed west through the Kill van Kull and south through the Arthur Kill. The peak water flux through the Arthur Kill is in excess of 400 m 3 s -1 . Stokes transport term contributed most towards upstream salt transport in Newark Bay and the Arthur Kill. In the Kill van Kull, the upstream salt transport is minimal. Salt flux through the Arthur Kill appears to be dominated by the elevation gradient between entrance to the Kill van Kull (from New York Harbor) and Perth Amboy. The salt flux through the Kill van Kull is influenced to a considerable extent (but not dominated) by the elevation gradient between the entrance to the Kill van Kull (from New York Harbor) and Shooters Island. The density gradient does not appear to be a predominant driving factor for the salt transport through the Kill van Kull and the Arthur Kill.

An operational forecast modeling system for the Mississippi Sound/Bight

An operational forecast modeling system for the Mississippi (MS) Sound/Bight has been developed. The system integrates a triple nested coastal ocean forecast modeling systems and a meteorological forecast model. The Mississippi Sound/Bight model based on ECOMSED, forms the central core of the operational forecast system. At its eastern and southern boundaries, the ECOMSED is coupled to a regional Gulf of Mexico (GOM) model in a manner that ensures seamless energy transfer between the two models. Meteorological forcing is provided by the Coupled Ocean/Atmospheric Mesoscale Prediction System, COAMPS. The forecast system automatically retrieves all available real-time river discharge data along the Gulf coast to be imposed as coastal boundary conditions. The operational MS Sound/Bight forecast model produces two 12-hour hindcast and two 48-hour forecasts everyday at 0000 and 1200 hours. The system is scheduled to run for 12 hours in a hindcast mode and then 48 hours in a forecast mode. However, these simulation periods can vary. Depending on the availability and lengths of inputs from the coupled GOM and COAMPS models, the operational system automatically sets the periods for hindcast and forecast simulations. The model saves the proper hydrodynamic information for a restart so that a smooth and seamless execution is possible to start the next cycle. All of the simulations of the model are performed and archived on the Major Shared Resource Center (MSRC) high-performance computers resident at NAVOCEANO, Stennis Space Center, MS. The archived model output includes hourly three-dimensional fields of salinity, temperature and currents and water level across the model domain. Quality control is performed before the results go to a post-processing phase. A post-processing routine, which runs autonomously, generates surface current, temperature and salinity distributions after the completion of each cycle of forecast. The model results are available on the NGLI website (www.navo.navy.mil/NGLI) for public use.

The calibration/validation of a Mississippi Sound/Bight model

A regional scale forecast modeling system of the Mississippi Sound/Bight and adjoining estuaries and bays has been developed as part of the Northern Gulf of Mexico Littoral Initiative (NGLI), a multi-agency program spearheaded by NAVOCEANO and USEPA Office of Gulf of Mexico Program. The system, based on the model called ECOMSED, provides a reliable means of predicting the littoral circulation and the salinity and temperature structure of the region. The modeling framework adopts a high-resolution orthogonal curvilinear grid which resolves the relevant bathymetric and coastline features, especially in the vicinity of the barrier islands and ship channels. In order to ensure that the model is capable of predicting the oceanography of the Mississippi Sound/Bight, a thorough calibration and validation effort has been conducted against field observations during September 2000. Point-to-point and spatial comparisons of sea surface elevation, temperature, salinity and water currents have been conducted. The calibration and validation efforts have been supplemented by rigorous analyses to understand the sensitivity of the model predictions to various forcing functions. The estuarine processes controlled by winds and freshwater discharges have been identified and quantified for Mobile Bay, Biloxi Back Bay, Bay St. Louis and Mississippi Sound/Bight through a series of model sensitivity simulations. Estimates of the variances in model predictions have been made using a First Order Variance Analysis (FOVA) method. Percent contribution of bathymetry, temperature and salinity boundary conditions, meteorological conditions and freshwater inflows to variances in model prediction has been determined. The bathymetry and freshwater flows are found to contribute most in the variances in temperature, salinity and transport in the Mississippi sound area. Where as wind plays a major role in the variances in model prediction in the Mississippi Bight (mid shelf) region. The ECOM model, calibrated and validated in this study, is currently in operational mode in the Major Shared Resource Center (MRSC) of NAVOCEANO at Stennis Space Center, Mississippi and the model results are available in the NGLI website at www.navo.navy.mil/NGLI.

Circulation, Sediment and Water Quality Modeling in the Northern Gulf of Mexico

The Northern Gulf of Mexico is an important area of interest from many perspectives, such as commercial, military and recreational. It is widely recognized as one of the top shell-fish producing and recreational regions in the United States and is a region where frequent military training exercises take place. To assist local, state and federal agencies plan for resource management and military training, a regional scale modeling system is being developed for these waters, that is, for the Mississippi Bight/Sound and adjoining Mobile Bay, Biloxi Bay, Bay St. Louis, and Lake Borgne. The modeling system, consisting of a three-dimensional circulation model, a cohesive and non-cohesive sediment transport model, a wave model, and a transport model will provide a reliable means to forecast littoral circulation, sediment suspension and transport, surface waves and conservative and non-conservative water quality constituents. The modeling framework adopts a high-resolution orthogonal curvilinear grid, which accurately resolves bathymetric and coastline features of the region, especially in the vicinity of the barrier islands. The southern model boundary follows the continental shelf break, roughly the 100m isobath, a natural dynamical barrier between the Sound and the rest of the Gulf of Mexico. This modeling system forms the highest horizontal resolution part of a triply nested series of three dimensional circulation models ranging from the North Atlantic Ocean to the Gulf of Mexico to the Mississippi Bight/Sound. Novel open boundary conditions are employed to couple all three parts of the system to one another. The Mississippi Bight/Sound model has been calibrated against water level data for the January – April 2000 period at several stations across Mississippi Sound. A more comprehensive model calibration/validation effort will also be discussed. Additional information on this effort may be obtained at www.navo.navy.mil/NGLI/main_frame.html.

Modeling the Stability of Contaminated Bed Sediments in a Shallow Lake

A sediment transport model was developed for Lake Waban, MA to evaluate the likelihood that selected areas of the lake would become recontaminated after removal of contaminated sediments from this area of the lake and to assess/quantify the transport of Lake Waban sediments towards and out to Lower Waban Brook. The model developed for this study (ECOMSED) consists of three separate models that were coupled together: hydrodynamic, windwave and sediment transport models. The model was used to simulate a base-case scenario representative of pre-dredging and post-dredging conditions for the year 2000 to evaluate the effect of sediment removal (dredging) operations in selected areas of the Northern Shoreline and Western Cove of the lake. The results of the simulation showed that Lake Waban is a low energy environment, and seems to be mostly depositional. There is relatively little change in sediment accretion for pre-dredging conditions as compared to post-dredging conditions. Sensitivity analyses were carried out for both pre-dredging and post-dredging conditions: (1) to evaluate the impact of no sediment inflow from Upper Waban Brook, and (2) to evaluate the impact of high winds (i.e., Logan Airport winds). Model results showed that sediment resuspension from other areas of Lake Waban does not contribute to significant sediment accretion in the dredging areas. The flux of sediment from Lake Waban to Lower Waban Brook was computed to be approximately 5 - 6 % of the sediment inflow for the simulated conditions.

Predicting Entrainment of Ichthyoplankton at a Power Plant Intake on the East River, NY

A random-walk particle-tracking model was developed for the East River, the New York Harbor, the Long Island Sound and the New York Bight to predict the distribution of ichthyoplankton and their probability of entrainment at the cooling water intake of the Charles Poletti power plant. The model was configured into a three-dimensional hydrodynamic and particle tracking model, ITM, which uses neutrally buoyant passive particles as surrogates for ichthyoplankton. In ITM, particles are transported by multidimensional advection and dispersion processes. The model was driven by time-dependent water levels, temperature and salinity along open boundaries, meteorological forcing and freshwater inflows. It was calibrated using observed surface and bottom salinity and temperature, water surface elevations and surface, mid-depth and bottom currents at locations across the New York harbor and the East River during 1994 and 1995. Results indicate that estuarine circulation greatly determined the distribution of particles in the East River. The probability that ichthyoplankton would be entrained into the Charles Poletti plant intake structure was highly dependent on the location and time of their release and the assumption that ichthyoplankton behave like neutrally buoyant particles.

Modeling Contaminated Sediments in a Shallow Bay

Operation of a leather tannery site adjacent to Tannery Bay (Michigan) has resulted in elevated concentrations of chromium in the bed sediments. Of concern is the potential resuspension of the sediments and their subsequent migration from the bay to the adjacent river. Evaluating the stability of these contaminated sediments is a necessary ingredient for developing sediment remediation strategies. An integrated hydrodynamic and sediment transport model was used to assess model response to (i) maximum probable flows, (ii) variable wind forcing, and (iii) variable resuspension potential parameters. A hydrodynamic model was used to determine current velocities and circulation patterns. This information was used to compute the bed shear stresses, which, in turn, controls sediment resuspension and deposition. Velocities predicted by the model were relatively low in the inner region of the bay indicating that the volume of sediment resuspended and transported to the adjacent river would comprise a small percentage of the contaminated sediments in the bay, even under the most extreme conditions considered. The sediment transport simulations were used to predict water column concentrations of dissolved chromium, which were found to be lower than the acute water quality criterion.

A Three-Dimensional Model for Cohesive Sediment Dynamics in Shallow Bays

The fate and transport of pollutants in aquatic systems is strongly influenced by cohesive sediment dynamics. This paper describes the development and validation of a high-resolution, three-dimensional, time-variable, cohesive sediment transport model of Green Bay. The model incorporates state-of-the-art cohesive sediment resuspension and deposition methodology, including bed armoring and flocculation. Resuspension and deposition are functions of bed shear stress due to wave-current interaction. To compute shear stresses and water column transport, hydrodynamic and wind-wave models of the bay were integrated with the sediment transport model. Boundary conditions at the Green Bay-Lake Michigan interface were derived from a coarser resolution hydrodynamic model of Lake Michigan. The model accounts for all significant sources of solids into the system including major tributaries, direct runoff, shoreline erosion and internal solids (i.e., algae) production. The model was simulated for a period of 516 days. Results indicated that the model was capable of reproducing the temporal variation of observed inorganic suspended sediment concentrations at 25 locations and annual sedimentation rates at 49 other locations.