Observing Large Waves Using Bottom-Mounted Pressure and Current Meters

This paper compares two different methods used for processing bottom PUV data to estimate the kinematics and summary statistics of large surface waves. The first method is based on linear wave theory (LWT). The second method is based on a new approach called the Directional Hybrid Wave Method (DHWM). The PUV data featured in this paper was measured 6 km offshore the mouth of the Columbia River, during fall-winter 1999, in a nominal water depth of 35 meters. This paper examined wave-wave interaction and wave-current interaction to assess the reliability of using linear wave theory and to enhance the utility of bottom PUV data in a water depth of 35 meters. Results of applying LWT and DHWM on PUV data were compared to wave-rider data, obtained from a NOAA buoy 14 km directly offshore from the point of PUV measurement. Results indicate that a current-induced Doppler effect can bias wave estimation by 2–10% and that LWT may have under estimated wave height by 20% during storms. The DHWM appears to offer much improvement over LWT and requires further investigation and verification.