was a Vitel Model WLS2 stilling well tide gauge with an air acoustic sensor to measure 

 the water surface elevation. These four gauges were surveyed in and their vertical datums 

 referenced to National Geodetic Vertical Datum (NGVD) 1929 as described in John E. 

 Chance & Associates (1996). The inlet throat and ocean wave gauges were also used as 

 tide gauges. However, these were not surveyed in. Instead, long-term average values were 

 used as reference mean water levels as described in Howell (1996). 



The bay pressure gauges were sampled at a 1-Hz rate. Water levels were reported as 

 6-min averages of these samples (360 data points). Measurements made between 1:00 and 

 1 :06 were reported as the 1:06 average. Water levels obtained from the six pressure 

 gauges needed to be corrected for changes in atmospheric pressure. This adjustment was 

 made by using another Paros pressure gauge housed in the data trailer as a barometer and 

 subtracting out the air pressure. Table 3 shows the availability of the water level data. 

 For the fully analyzed data, the elevations are available in meters relative to NGVD 1929 

 (approximately mean sea level). 



The Paros gauges were calibrated before deployment. Their resolution is approxi- 

 mately ±2 mm, and their precision is on the order of ±1 cm. Examples of the water level 

 data from the three time periods of interest are given in Chapter 3 . 



Current Measurements 



The current meters were RD Instruments broad band 1 ,200-kHz Acoustic Doppler 

 Current Profilers (ADCPs). These instruments were mounted horizontally on the same 

 pods as the DWG Is and were oriented upward-looking through the use of a right angle 

 head. Each shared a data and power cable with the wave sensors. For further information 

 on this instrument, see the RD Instruments World Wide Web site (http://www.adcp.com/). 



The ADCPs divided the water column into a maximum of 13 vertical bins, each 0.5 m 

 long, and computed velocities in each bin. As is typical with ADCPs, data collected at the 

 top and bottom bins were not usable. The ADCPs sampled at 1 Hz. The samples were 

 first decimated to 0. 1 Hz, then averaged in 6-min intervals, then bins 3 through 5 were 

 averaged together (creating a 6-min average of the velocity between 1.0 and 2.5 m above 

 the bed). The east/west and north/south components of these 6-min averages were 

 reported in meters per second (north and east directions are positive). The time stamp 

 associated with each average refers to the time at the beginning of the average. 



Table 4 shows the availability of the current data. However, these data have recently 

 been found to have a problem with the time code. This problem is under review, and thus, 

 these data are not generally available for public release. 



Chapter 3 gives examples of these data. In addition, Appendix A contains a report of 

 the ADCP current measurements made during the short-term experiment (August and 

 September 1997). A neap tide current survey was conducted on 25-29 August, and a 

 spring tide current survey was conducted 2 weeks later on 15-19 September 1997. 



1 Chapter 2 Instrumentation and Procedures 



