Field Measurements of Inhomogeneous Wave Conditions in Bjørnafjorden

Abstract

Due to the complex topography in a fjord, wave conditions differ from those of ocean waves. In this study, characteristics of wave conditions in the Bjørnafjorden in Hordaland County, Norway were thoroughly investigated based on field measurements. Bjørnafjorden is approximately 4,600 m wide and more than 500 m deep, with a complex hydrography and topography. Three Datawell Waveriders (DWRs, Datawell, Haarlem, Netherlands) were deployed to measure the wave data. Due to two ferry routes nearby, the measured raw data were found to be influenced by ship waves. Thus, a band-pass filter based on wavelet and inverse wavelet analyses was proposed and developed to detect and remove ship waves from raw data. The wave data analyzed were measured over approximately 19 months. The wave conditions measured by each DWR were characterized by several parameters, such as significant wave height, average zero upcrossing period, and dominant direction. The values of each wave parameter at each DWR usually differed, which indicates that the wave field in Bjørnafjorden is inhomogeneous. The statistical values of these parameters among the three DWRs were correlated to some extent. Their distribution could not be fitted by a suitable distribution function unless more data were available. The coherence among the three DWRs was fairly low.