Current measurements offshore Humboldt Bay California for proposed ocean outfall

Extensive Current Studies have been completed for a proposed ocean outfall off Humboldt Bay, California. The Studies combined both Lagrangion and Eulerian current measurement techniques. To assist in the interpretation of the data obtained by the different techniques, a series of verification experiments were performed. Currents were monitored continuously during a one year period using in-situ recording meters. The major concern governing the selection of the instruments was the severe wave climate off Humboldt Bay, which affected the accuracy of the measurements and the survivability of the instruments. Endeco tethered current meters were utilized. The instrument mooring tether was empirically adjusted to achieve maximum data recovery following initial installation. A series of drogue and drift card releases were performed. The drogues consisted of 25 foot (7.6 meter), diameter parachute type with surface marker buoy. Position of the drogue was monitored at 1/2 hour intervals during a 24 hour period, or, until the drogue moved beyond the study area.Drift card returns were aided by regular surveys of the beaches in the area. Due to certain discrepancies between the vector average velocities obtained with the current meter and the drogues, the in-situ current meter verification experiments were performed. These consisted essentially of a series of window shade drogue releases which were tracked to provide detailed velocity data in the immediate vicinity of the current meter array over a period of several hours.