Theoretical and computed discharge-coefficient ratings for submerged orifice and weir flows were determined at seven coastal control structures, and discharge ratings for free orifice and weir flows were determined at three coastal control structures. The difference between the theoretical and computed discharge-coefficient ratings varied from structure to structure. The theoretical and computed discharge-coefficient ratings for submerged orifice flow were within 10 percent at four of seven coastal control structures; however, differences greater than 20 percent were found at two of the seven structures. The theoretical and computed discharge-coefficient ratings for submerged weir flow were within 10 percent at three of seven coastal control structures; however, differences greater than 20 percent were found at four of the seven coastal control structures. The difference between theoretical and computed discharge-coefficient ratings for free orifice and free weir flows ranged from 5 to 32 percent. Some differences between the theoretical and computed discharge-coefficient ratings could be better defined with more data collected over a greater distribution of measuring conditions.
The ADCP has many advantages over the commonly used Price meter. An ADCP measurement can be made in minutes, as opposed to the longer time required by the Price meter. This speed allows for a more accurate collection of data in dynamic conditions, such as those encountered in this study. For example, a discharge measurement could be taken before water levels and average channel velocities have changed substantially. Another advantage of the ADCP over the Price meter is that data are collected on a continuum in the water column and cross section rather than at discrete points.
Generally, ADCP measurements were made simultaneously by the USGS and SFWMD at the coastal hydraulic control structure sites. Access to all the sites was made upstream, and a small boat was adequate in almost every situation. Boats had ADCP's mounted on their bows and faced the flow. Taglines were stretched across the canals for pulling the boat slowly across the water to obtain the measurements. Upstream and downstream stages were noted at the beginning and end of every measure- ment.
When gate openings were planned for a given day, discharge measurements were made repeatedly at discrete gate openings. Using the ADCP, measurements were made quickly and repeatedly during relatively rapid gate operations. All concurrent water-level, gate opening, and discharge data were collated and analyzed with a spreadsheet program. Flow regimes were identified, and a least squares fit was used to determine the best estimate of the appropriate coefficients.