present little above surface exposure reducing wind effects. The 

 analysis of circulation patterns was based on the limited current meter 

 data and on returns from about 4,000 surface and seabed drifters, re- 

 leased during 1969. The history of returns for these drifters is 

 shown in Figure 10. Details on the construction and operation of drif- 

 ters can be found in papers by (Bumpus, (1965), Harrison, et al , (1967). 



a. Surface Circulation . Knowledge of surface currents is important 

 in understanding the dispersion of surface pollutants near the dumping 

 grounds. Surface circulation of the waters of the Bight is controlled 

 by tides and prevailing winds. It is difficult to determine the net 

 effect of tidal and wind-driven surface circulation on waste dispersion 

 in the absence of comprehensive synoptic hydrographic surveys, because 

 both tides and winds are dependent on time of day and season of year. 

 However the following general remarks can be made: 



(1) Tidal Circulation . The New York Harbor tidal circulation 

 has been studied by Marmer (1935), and Jeffries (1962). Under flood 

 conditions, water flows into the Lower Bay through Ambrose Channel while 

 ebbing still occurs at the surface and along the bottom of the channel. 

 The ebb in the Lower Bay is generally stronger than the flood by 10 

 percent or more, so, in addition to the net transport of water from the 

 Hudson River, there is a net flow of water in a seaward direction. Net 

 currents in Raritan and Lower Bays are shown in Figure 11. The tidal 

 pattern in Upper Bay, south of Manhattan, is complicated by cross currents 

 due to differences in ebb and flood, and effects of tidal resonance. 

 Tidal currents in the Narrows are quite strong. 



The nearshore tidal circulation, along the New Jersey and Long Island 

 coasts near the entrance to the Harbor, is quite different than the off- 

 shore circulation. According to the United States Coast Pilot for Area 2 

 (Cape Cod to Sandy Hook), tidal currents near the Fire Island Lighted 

 Whistle Buoy, have a mean velocity of about 0.2 knots west on the flood 

 and east on the ebb. At the seaward end of Ambrose Channel, the mean 

 velocity of the tidal currents at flood is 1.7 knots, at ebb, 2.3 knots. 



Tidal currents are less significant offshore of the present dumping 

 grounds than in the nearshore area. Velocities are probably no more than 

 0.3 knots shifting direction continuously to the right in a clockwise 

 direction with each tidal cycle of about 12.4 hours. This direction shift 

 would have an average rate of about 30' per hour and would have the effect 

 of isotropically dispersing any suspended lightweight material in the 

 upper part of the water column. 



(2) Wind-Driven Circulation . Wind-driven circulation in the 

 New York Bight is far more significant than tidal circulation in the 

 dispersal of suspended waste material in the surface waters. Circulation 

 of surface water due to wind-driven surface currents at the ocean dump- 

 ing grounds similarly cannot be deduced without synoptic field investi- 

 gations and measurements. On the basis of known wind patterns, the 

 following generalizations can tentatively be made. 



41 



