Richard I. Hires

A Three-Dimensional Simulation of the Hudson–Raritan Estuary. Part II: Comparison with Observation

Abstract Results from a time-dependent, three-dimensional numerical simulation of the Hudson–Raritan estuary are compared with observations. The comparison includes: 1) instantaneous salinity contours across a transect in the estuary; 2) amplitudes and phase of tidal constituents at four tide gauge and five current meter stations, 3) mean currents at nine meter locations, and mean salinity in the Hudson River, 4) kinetic energy spectra; and 5) response to wind forcing of subtidal current at an observational station near the mouth of the estuary. Observations confirm the models prediction of existence of density advection instabilities induced by differential advection of the three-dimensional density field. These instabilities produce intense vertical mixing and should significantly modify dispersion processes in the estuary. Effects of neap–spring tides on vertical stratifications are also simulated by the model. Simulated M2 phase at three tide gauge stations show improvement over the M2 phases obtaine...

Heavy metal distribution in Newark Bay sediments

Abstract Bottom sediments have been analysed from Newark Bay, New Jersey, for zinc, lead, cadmium, and mercury. The bottom sediment analyses show that the bay sediments are enriched over background levels up to 65 times for zinc, 128 times for lead, 180 times for cadmium, and 155 times for mercury. Analyses of the metal distribution and of available tidal hydraulic data indicate the metal concentrations are due to a combination of source and tidal hydraulics. Dye tracer experiments gathering Lagrangiantype data appear to yield the best result in the investigation of metal trasport phenomena.

Laboratory measurement of bottom shear stress on a movable bed

A shear plate was developed to obtain direct measurements of bottom shear stress under nonbreaking surface gravity waves on a movable sand bed. The experiments were conducted under regular wave conditions in a large wave tank where time histories of bottom shear stress and surface elevation were obtained from a shear plate and wave gauges. Measurements were made at scales approaching those encountered in the field. These data were obtained under steep, vortex ripples where form drag dominated over skin friction for all data presented. Wave friction factors were calculated from measurements and were compared with existing theories as well as with previous laboratory studies. Values of the wave friction factor obtained using the shear plate exhibited reasonable agreement with existing theory. Close agreement between values of the wave friction factor obtained from the shear plate and those measured by previous studies demonstrates that use of a shear plate is a reliable additional method for the measurement of bottom shear stress over a movable bed in the laboratory.

A Three-Dimensional Simulation of the Hudson–Raritan Estuary. Part III: Salt Flux Analyses

Abstract Salt fluxes and volume transports in an estuary vary considerably over subtidal time scales of a few days to weeks in response to wind and neap–spring tidal forcings. Results from a numerical simulation of the Hudson–Raritan estuary are used to study subtidal variations of salt fluxes and the physical mechanisms for salt balance in the estuary. Simulated salt fluxes are compared with available observations. Observations support the models finding that analysis of volume and salt fluxes based on short-length data records (<30 days) can lead to misleading conclusions. “Tidal trapping” effects due to coastline irregularities contribute most to the salt balance at the Sandy Hook–Rockaway Point transect and at the Narrows. A two-week observational record is analyzed to support this finding. Simulated subtidal variation of the tidal trapping term at the Sandy Hook–Rockaway Point transect compares well with that observed. In Raritan Bay, where tidal currents are weak and effects of winds are significan...

Tidal modeling of the Hudson-Raritan Estuary

Abstract Tidal flow characteristics in the Hudson-Raritan Estuary are studied with a two-dimensional, depth-averaged finite difference model. Rivers are modeled as one-dimensional channels with variable width and depth and are calculated as part of the two-dimensional calculations at no extra computational cost. An extensive comparison of numerical, tidal calculations with observational data than has previously appeared in the literature is presented. Computed velocity and tidal elevation fields compare well with observations. Comparison with observations at the Sandy Hook-Rockaway Point transect indicates that the barotropic tidal residual current contributes significantly to the overall steady circulation in the harbor. The residual current is mainly induced by the coastal geometry and bottom topography through the nonlinear inertia effects.

Partial recovery of Newark Bay, NJ, following pollution abatement

Abstract For the seven months terminating on 17 August 1980, primary sewage effluent was discharged into Newark Bay. From 22 July to 6 October 1980, we collected physical, chemical and biological data in the Newark Bay estuary from the lower Passaic River to New York Harbor. During the period of maximum discharge, the Passaic River and much of Newark Bay were anoxic or nearly so. Recovery of the Newark Bay water following sewage abatement took approximately 30 days. During most of the study period, a bloom of blue-green algae characterized the ‘Passaic River water’. This water was also characterized by chlorophyll-a values as high as 73 mg m −3 . Chlorophyll concentration almost always increased up the bay, along with decreasing salinity, increasing temperature, increasing phosphate-P and decreasing nitrate-N. The decrease in nitrate, however, was associated with an increase in ammonia-N and total N during the period of sewage discharge.

MEASUREMENT OF SHEAR STRESS ON A MOVEABLE BED

Detailed studies have been undertaken to assist in the design of major extensions to the port of Haifa. Both numerical and physical model studies were done to optimise the mooring conditions vis a vis the harbour approach and entrance layout. The adopted layout deviates from the normal straight approach to the harbour entrance. This layout, together with suitable aids to navigation, was found to be nautically acceptable, and generally better with regard to mooring conditions, on the basis of extensive nautical design studies.Hwa-Lian Harbour is located at the north-eastern coast of Taiwan, where is relatively exposed to the threat of typhoon waves from the Pacific Ocean. In the summer season, harbour resonance caused by typhoon waves which generated at the eastern ocean of the Philippine. In order to obtain a better understanding of the existing problem and find out a feasible solution to improve harbour instability. Typhoon waves measurement, wave characteristics analysis, down-time evaluation for harbour operation, hydraulic model tests are carried out in this program. Under the action of typhoon waves, the wave spectra show that inside the harbors short period energy component has been damped by breakwater, but the long period energy increased by resonance hundred times. The hydraulic model test can reproduce the prototype phenomena successfully. The result of model tests indicate that by constructing a jetty at the harbour entrance or building a short groin at the corner of terminal #25, the long period wave height amplification agitated by typhoon waves can be eliminated about 50%. The width of harbour basin 800m is about one half of wave length in the basin for period 140sec which occurs the maximum wave amplification.Two-stage methodology of shoreline prediction for long coastal segments is presented in the study. About 30-km stretch of seaward coast of the Hel Peninsula was selected for the analysis. In 1st stage the shoreline evolution was assessed ignoring local effects of man-made structures. Those calculations allowed the identification of potentially eroding spots and the explanation of causes of erosion. In 2nd stage a 2-km eroding sub-segment of the Peninsula in the vicinity of existing harbour was thoroughly examined including local man-induced effects. The computations properly reproduced the shoreline evolution along this sub-segment over a long period between 1934 and 1997.In connection with the dredging and reclamation works at the Oresund Link Project between Denmark and Sweden carried out by the Contractor, Oresund Marine Joint Venture (OMJV), an intensive spill monitoring campaign has been performed in order to fulfil the environmental requirements set by the Danish and Swedish Authorities. Spill in this context is defined as the overall amount of suspended sediment originating from dredging and reclamation activities leaving the working zone. The maximum spill limit is set to 5% of the dredged material, which has to be monitored, analysed and calculated within 25% accuracy. Velocity data are measured by means of a broad band ADCP and turbidity data by four OBS probes (output in FTU). The FTUs are converted into sediment content in mg/1 by water samples. The analyses carried out, results in high acceptance levels for the conversion to be implemented as a linear relation which can be forced through the origin. Furthermore analyses verifies that the applied setup with a 4-point turbidity profile is a reasonable approximation to the true turbidity profile. Finally the maximum turbidity is on average located at a distance 30-40% from the seabed.

Predictor-Independent Linear Models Relating Lognormally Distributed Escherichia coli and Fecal Coliforms

AbstractFollowing an EPA recommendation many states switched to Escherichia coli (EC) water-quality standards. However, past data is still in terms of fecal coliforms (FC). EC-FC models are therefore necessary to understand long-term water-quality trends. The predominant method develops a linear relationship between log EC and log FC by minimizing the errors of log EC. These models are difficult to interpret as they are nonlinear. This method also leads to biased model coefficients as log FC is assumed to be error free. The present study develops linear models that do not require predictor identification. The models were developed by minimizing the errors in the logarithmic domain. Linear and log-log models with and without predictor identification were developed for EC-FC data from 10 sites in the lower Passaic River at Paterson, New Jersey. The Nash-Sutcliffe efficiencies (NSEs) of all model types are similar. The authors recommend the use of linear models that do not require predictor identification du...