essentially continued, with some modification, throughout the history of 

 the country. Eventually, a national network of permanently operating 

 water-level measurement stations was established to support the charting 

 activity. 



Long-term tidal measurements from the U.S. Coast and Geodetic 

 Survey were the basis for establishing a boundary indicating ownership 

 between private upland and sovereign submerged lands (the landmark case 

 Borax Consolidated, Ltd. vs. Los Angeles, circa 1935; see Shalowitz 

 (1964)). The result of this decision by the U.S. Supreme Court was 

 carried over by the state courts to be the accepted method for dealing with 

 boundary issues. An 18.6-year water-level record, which corresponds to a 

 complete cycle of progression of the moon's nodes along the ecliptic 

 (described by Meton in the fifth century before Christ), is believed to 

 account for all the astronomical variations in the ranges of the tide. 



Also, it was believed for many years that the tides rose and fell 

 periodically and the application of a mean high water was appropriate for 

 all coastal waters. However, as more long-term tide stations have been 

 operated throughout the United States, we have found that the 

 astronomical gravitation is not always dominant. The tidal force is 

 frequently exceeded by meteorological forces, acting both over the long 

 term (seasons) and in the short term (hours and days through strong winds 

 and changes in air pressure accompanying passage of weather fronts). 

 Meteorological forcing can be particularly significant in shallow-water 

 bodies, such as along the Texas coast. Observations from the TCOON 

 have clearly shown that tidal datums established through traditional 

 procedures are not well-suited within the bays and estuaries along the 

 Texas coast for boundary, regulatory, or navigational purposes. 



Water Level and Tidal Datums 



This section reviews key concepts and notation relevant to the needs 

 assessment. Definitions of tidal datums and associated nomenclature and 

 concepts can by found in the NOS "Tide and Current Glossary" (Hicks 

 1989), in a US ACE Special Report (Harris 1981), in the US ACE Engineer 

 Manual entitled "Water Levels and Wave Heights for Coastal Engineering 

 Design" (US ACE 1989), and in the EM entitled "Hydrographic 



1 Chapter 2 Water Level Definition, Measurement, and Properties 



