Wave Pressure Gauge Analysis with Current

Abstract

Bottom-mounted pressure gauges are used to measure waves in coastal inlets, where tidal currents are significant. Theoretically, neglect of the current in analysis of pressure data can lead to order-one errors in wave height estimates. Wave height is overestimated by neglecting flood current and underestimated by neglecting ebb current. A collocated wave buoy and bottom-mounted pressure gauge were deployed at Willapa Bay, Washington, to evaluate the significance of including current in pressure data analysis. Wave heights were overestimated by up to 20% if current was neglected. Larger current-induced errors in wave height were prevented by truncation of high-frequency energy to exclude pressure system noise. Truncation of the spectra leads to overestimates of mean wave period and underestimates of wave height. Adding a theoretical tail to the spectra reduces truncation errors. If current measurements are not available for pressure gauge analysis, reasonable results can be achieved by applying a conservative high-frequency cutoff and adding a theoretical tail.