Tidal current cycle observations for support of the NOS/USPS tidal current prediction quality assurance program

"Accurate tidal current predictions are essential to the safe passage, docking and undocking of vessels ranging in size from privately owned yachts to large tankers navigating the Nation's waterways. The National Ocean Service (NOS) of the National Oceanic and Atmospheric Administration (NOAA) publishes annual tidal current predictions for more than 2900 locations. NOS collects circulation measurements, analyzes the data, computes harmonic constituents describing the tidal current, and generates harmonic predictions of the tidal current based upon astronomical factors. Tidal currents are very sensitive to the effects of sediment accretion and erosion, dredge operations, and marine construction projects. NOS measurements supporting the tidal predictions are typically several decades old and of only a few days duration. The reoccupation of a location to evaluate predictions is seldom accomplished owing to the great expense in time and money. Consequently, the accuracy ol the corresponding NOS tidal current predictions are degraded to an unknown extent by changes in the basin. Recently, the U.S. Power Squadrons (USPS) volunteered to reoccupy and measure currents at the site of NOS predictions. NOS will then compare observed and predicted times of selected tidal cycle events to give a qualitative and perhaps quantitative measure of NOS tidal current prediction accuracy. Discrepancies will be documented in the Notice to Mariners and possibly demonstrate a need for more comprehensive NOS surveys of selected areas."