Example of Need for Gauges 



The inland bays and estuaries along the Texas coast are connected to 

 the Gulf of Mexico through narrow and, in some cases, shallow openings 

 in the barrier islands. As the tidal movement from the Gulf progresses 

 through these openings, it is diminished by the restrictions and by friction. 

 The astronomical force becomes weak compared to the strong 

 meteorological forces and is frequently masked and impossible to 

 consistently identify. The masking makes the computation of a tidal 

 datum difficult or impossible in the traditional manner. Kraus and 

 Militello (1996) document wind setup and setdown of water level on the 

 eastern and western ends of East Matagorda Bay, Texas, and found a 

 difference of 2 ft in water level at opposite ends of the bay produced by a 

 winter northern front, with 1-ft differences occurring almost weekly in 

 winter. The tidal range in East Matagorda Bay is only 0.4 ft. 



Much of the area within the navigational waterways is nontidal, which 

 has been observed from historic data and existing TCOON stations (Gill, 

 Hubbard, and Dingle 1995). Where tidal datums cannot be determined, 

 stations will need to be spaced to determine and record variability in 

 elevations within each area. An example of such variability is shown in 

 Figure 1 1 , which is a plot of simultaneous records from three stations in 

 the Land Cut in the Laguna Madre. The stations, going from north to 

 south, are Yarborough (004), EL Toro (007), and Rincon de San Jose 

 (003), which are located approximately 15 miles apart. 



The horizontal axis plots time and covers a 2-day period. The vertical 

 axis represents the height of the water in feet. The three records are 

 plotted on the individual station datums or zeros, which are arbitrary and 

 have no direct height relationship between stations. The purpose of the 

 graph is to demonstrate how the water level changes between stations 

 within close proximity. The water level can be rising in one area, but 

 falling in another area just a few miles away. The downward pointing 

 spikes in the records are probably associated with the drawdown 

 accompanying the passage of barges. By associated pairs of spikes with 

 the passage of the same barge tow at El Toro and Rincon, the speed of the 

 barges can be estimated. 



42 Chapter 5 Consideration of an Expanded Network 



