Data are collected along 9 to 12 transect lines covering the 7.1-km segment of C-111 beginning 1.1 km north of US Hwy 1 bridge and ending 2 km south of S-18C. Transects originate at locations on the southwest bank of the canal opposite culverts under the levee road on the northeast bank and extend normal to the canal approximately 1.5 km into the adjacent wetlands. Transects lines are numbered 1 through 9 beginning with the culvert nearest US Hwy 1 bridge. Measurement sites are spaced at variable-length intervals along the transect lines.

Five basic water-quality parameters (temperature, pH, specific conductance, dissolved oxygen, and salinity) are collected at each site having sufficient depth using a Hydrolab multi-parameter sensor positioned at mid-depth.

Flow data at each site consists of velocity measured at three points in the water column for depths greater than 15 cm. Measurement points in the water column are referenced to the water surface and are located generally at 0.8, 0.6, and 0.2 depth. For depths less than 15 cm a single velocity measurement is made at mid-depth (0.5d). Velocity vector components Geodetically referenced to east, north, and up directions are obtained from Sontek Acoustic Doppler Velocimeters (ADV) suspended from and positioned using modified wading rods. Velocities are sampled at each depth in the water column for 2 minutes at a frequency (typically 10 or 18 Hz) set by the user. Four files of information (control, velocity, correlation, and signal-to-noise ratio) are obtained for each measurement. Sontek-provided software are used to download and extract these individual files for post-processing from the primary ADV file recorded in the field.

Raw flow-velocity component data, made available for downloading, are provisional, minimally processed, and subject to revision. All four sets of information identified above are included in the raw data file. All data meet the criterion of a correlation value above 70 % as suggested by Sontek (Sontek, 1996). Sontek also suggests a signal-to-noise ratio greater than 15 dB at 25 Hz and greater than 5 dB at 0.1 Hz. Measurements were generally taken at 10 or 18 Hz. The average signal-to-noise ratio for each direction component is found to be greater than 5 dB. The average and standard deviation of velocity, correlation, and signal-to-noise ratio for each velocity component are given in the summary file.

Sontek Technical Notes - Acoustic Doppler Velocimeter (ADV) Principles of Operation, (15 Oct. 1996)

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