Appendix C 



Adjustment of 1 933 Hydrographic 



Data to Modern Datum 



Adjustment for Sea Level Rise: 



Battery, NY, sea level trend (from National Oceanic and Atmospheric Administration (NOAA) 

 Internet site): 2.72 mm/year = 0. 107 in./year = 0.0089 ft/year 



Time interval: 1996 - 1933 = 63 years 



Adjustment: 0.0089 ft/year * 63 year = 0.56 ft 



Note: Water now is 0.56 ft higher than in 1933, so we must add 0.56 ft to water depths (i.e., 

 if in 1933 a point was -10.0 ft, it now would be -10.56 ft assuming not changes in seabed) - see 

 Figure El a. 



Datum: 



At Shinnecock: Mean low water (MLW) to National Geodetic Vertical Datum (NGVD) (1929 

 adj.): 1.10 ft 



Note: NGVD is 1.10 ft higher than mlw, so we must add 1.10 ft to depths (Figure Elb). 



Total correction: 



0.56+ 1.10= 1.66 ft (Figure El c) 



Appendix C Adjustment of 1933 Hydrographic Data C1 



