Doppler Acoustic Current Measurements in High Currents

In preparation for platform installation, Marathon Oil Company and Evans-Hamilton, Inc. designed, deployed and successfully retrieved an internally-recording Doppler current profiling package in Upper Cook Inlet. The strong currents, shipping, and large tide range, together with the requirements for a complete profile of current measurements, precluded the use of conventional moored current meters; thus a compact bottom-mounted package was deployed. An RD Instruments Acoustic Doppler Current Profiler, an InterOcean S-4 current meter, and a Sea Data TDR tide gauge, all supplied by Coastal Leasing, Inc., were deployed in 55 meters of water. Every half-hour, 5-minute average current profiles with 30 2-meter depth cells were recorded by the profiler. The S-4, at the 1.5-meter elevation, sampled at the same rate; thus a reliable profile of the currents was collected from 1.5 meters above the bottom to within 9 meters of the surface in the presence of 7-knot currents and a 7-meter tide range. Consistency checks with past results and between the two systems are presented, problems encountered are discussed and representative data are shown.