Table 7 



Shinnecock Inlet, Atlantic Ocean: Elevations of Tidal Datums Referred to Mean 



Lower Low Water 1 



Tidal Level 



Elevation (m) 



Highest observed water (12/25/1978) 



2.19 



Mean higher high water (mhhw) 



1.15 



Mean high water (mhw) 



1.06 



Mean tide level (mtl) 



0.56 



NGVD 1929 



0.38 2 



Mean lower water (mlw) 



0.049 



Mean lower low water (mllw) 



0.00 



Lowest observed water level (3/28/1979) 



-0.51 



'Elevations from U.S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA). 

 Publication date: 7/20/1987 (NOAA 1987). 



2 NGVD based on data from USAE District, New York, surveyors (elevation of 4.13 m (13.54 ft) measured at bench 

 mark No. 1,1974). 



were observed at the east side. The maximum average speed at Shinnecock Inlet was 1.6 m/sec 

 with instantaneous speeds exceeding 2.1 m/sec. The 1991 survey also established two current 

 measuring stations within Shinnecock Bay (S-4 and S-5) to assess the strength and direction of 

 tidal currents at the bay channels north of the inlet (Figure 16). Ebb currents had approximately 

 the same strength at both locations, around 1.3 m/sec. However, flood currents at S-5 were 

 weaker than those at S-4. During flood tides, the currents at S-4 and S-5 both moved in a 

 westerly direction, suggesting that there may be a clockwise circulation in Shinnecock Bay 

 (USAEWES 1991). 



The 1992 current study was conducted during an average tidal height condition for the area, 

 while the 1993 survey was planned specifically for a spring tide condition. The peak flood flow 

 in 1992 was about 1,800 m 3 /sec (63,600 ftVsec), which was 20 percent higher than the peak ebb 

 flow of 1,500 m 3 /sec (53,000 ftVsec). The 1993 spring tide survey showed a peak flood flow of 

 2,940 m 3 /sec (104,000 ftVsec), which was about 23 percent higher than the ebb flow of 

 2,400 m 3 /sec (84,800 ftVsec). Normal flood tides last approximately 5 hr and 40 min, while 

 normal ebb tides last about 6 hr and 40 min (USAEWES 1993). 



Results of the 1994 study indicated that the peak flood flow was approximately 2.4 m/sec at 

 the inlet entrance. Current distribution also showed a shift of the flood current to east of the 

 center of the inlet. This shift is thought to result from the filling of the scour hole and tightening 

 of the east jetty. Tidal prisms computed from the 1992 and 1993 surveys are shown in Table 8 

 (USAEWES 1995). 



Chapter 3 Physical and Coastal Processes 33 



