7, the current velocities in channels A and B were 

 matched at 13.1 cm/sec. Thereafter, the post- 

 dredging velocity in channel B was greater than 

 in channel A, i.e., 18.0 cm/sec at station 5 and 

 7.2 cm/sec at station 6. Thus, maximum flow was 

 changed from channel A to channel B as a result 

 of the dredging. 



Channel B was converted from a shallow, wide 

 passage with maximum surface area in contact 

 with the current (hence maximum friction and 

 impedance of water flow) to a deep channel, whose 

 depths at mean low water before and after 

 dredging were 0.4 m and 2.1 m at the entrance. 



The substratum of channel A was gravel and 

 sand at the most westerly end, changing to sand 

 for most of the length of the channel as it passed 

 islands I and II, after which it gradually became 

 muddy sand. Near Thyone Cove only the shoreline 

 and 3 m of littoral remained muddy sand; below 

 this level the substratum was gray sand covered 

 by 2 cm of silt. 



As indicated earlier, channel B had a lower 

 velocity before dredging than channel A. The 

 transitional area was compressed in channel B; 

 the area of sand at the westerly end merged 

 rapidly into muddy sand, then silt, a short 

 distance past the easterly end of island I. 



Channel C, both pre- and postdredging, was 

 characterized by an initial high velocity (55.17 

 cm/sec at station 2 and 38.40 cm/sec at station 

 2D), but this rapidly dissipated over the sand flats 

 and eddies north of islands III and IV. 



Maximum surface and bottom velocity was 

 halved after dredging at the inlet to the bay. This, 

 of course, would have a most profound influence 

 on transport of materials, since it represented a 

 section of water approximately 22 m wide by 2.8 m 

 deep. Since the original mean depth of the channel 

 was approximately 1 m, the cross section of the 

 dredged channel was approximately three times 

 greater than the original channel, increasing its 

 volume commensurately. 



Isaac (1965) stated that current velocities of 0.6 

 to 1.3 ft/sec (18.29 to 39.62 cm/sec) are sufficient 

 to resuspend bottom deposits with 1 .0 mm particle 

 diameter. According to changes in current 

 velocity at Goose Creek, the deposition of such 

 particles would have taken place at the following 

 stations after dredging, although not before dredg- 

 ing: station 7 (41.4 to 13.1 cm/sec), station 6 (40.2 

 to 7.2 cm/sec), station 3 (43.9 to 2.6 cm/sec), 

 station 4 (23.2 to 13.1 cm/sec) and station 2D 

 (38.4 to 5.5 cm/sec). 



FISHERY BULLETIN: VOL. 72, NO. 2 



Mass Movement of Water 



Hair (1968) calculated the volume of water 

 moving in and out of Goose Creek during each 

 phase of the tidal cycle. Assuming the average 

 depth to be 1.3 m at high tide with a tidal range 

 of0.8mandanareaof2.59 x lO^m^, he calculated 

 the volume of the bay at high tide to be 3.88 x 

 lO^m^. At low tide the corresponding 

 calculation was 1.44 x lO^m^. The volume lost 

 at each falling tide would then represent approxi- 

 mately 60% of the volume at high tide. Fazio 

 (1969) recalculated the tidal exchange on the 

 basis of the increased volume of the bay caused 

 by the construction of the dredged channel. His 

 volumes were 7 x lO^m^ at high tide and 3.1 x 

 lO^m^ at low tide. This represents a loss of 66% at 

 each ebb and is considered by Fazio as a corrobora- 

 tion of Hair's calculations. 



Of importance in any consideration of the 

 benthos in Goose Creek is the fact that during 

 the 6 h of ebb tide roughly 60% to 66% of the 

 total volume of water in Goose Creek (approxi- 

 mately 2 X lO^m^ before dredging and 4 x lO^m^ 

 after dredging) flowed out of the bay. All of this 

 water passed through channels A, B, and C 

 which, at a maximum value of 23 m wide and 

 3.0 m deep for channel B and 30 m x 1.5 m for 

 the combined channels A and C, represents a total 

 cross-sectional volume of 114 m^ for the passage 

 of ca. 3.9 X lO^m^ of water. The relatively small 

 volume of channels A, B, and C and the 244 m 

 channel formed by their confluence and flowing 

 eastward into Southold Bay accounts for the 

 rapid current velocity in the eastern half of 

 Goose Creek. 



On 21 May 1966, an attempt was made to 

 determine the proportion of water exchanged in 

 various parts of the bay. Rhodamine B was 

 released into the easternmost portion of Goose 

 Creek (near the bridge) on an incoming tide, so 

 that the average dilution was approximately 27 

 ppm after 2 h over the entire surface area of 

 the bay. Six weeks later the readings on the 

 fiuorometer revealed values of the order of 1.7 

 ppm in most of the eastern half of the bay while 

 Thyone Cove and the western shore of Goose 

 Creek had readings as high as 9.6 ppm and lows 

 rarely below 6.3 ppm. 



Figure 5 demonstrates that the exchange of 

 water, as revealed by residues of Rhodamine 

 B, was greater in the eastern half of the bay, with 

 areas of Thyone Cove and the west shore having 



452 



