SFY: A free-drifting wave buoy for measuring surf waves

Abstract

Breaking waves have been studied for over a century. Still, there is an insufficient understanding of wave breaking due to limited in situ data. The high variability and the energetic environment in the surf zone makes it very challenging to collect data of surfing waves such as plunging and spilling breakers. The many variables needed to create good surf conditions are interwoven and several are examined in this thesis such as wave breaking, wave height, wave period, wind and currents. The goal of this project is to test a very small free-drifting wave buoy (SFY) in the surf zone and near-shore areas. The data will be used to examine if the SFY can provide useful infor- mation describing the actual surfing conditions. The SFY has a sample rate of 52 Hz which allows it to capture breaking waves. In this project, 15 days of surf wave experiments were performed at 11 different surf spots in Norway. Throughout the field experiments the waves were varying in size from 0.2 m to 1.5 m and wind conditions from light offshore winds to strong cross-shore. The SFYs captured four individual wave breaking event at popular surfing locations such as Point Perfect, Unstad Left, Elvenes and Fuglingen. The data from a moored SFY outside the surf zone showed that the SFY can separate between "swell waves" and "wind waves" which are crucial surf variables. The SFY has also the potential of measuring the wave types of surfing waves. During this study, the best surfing conditions were found at Unstad Left. The SFYs primarily moved with the surface current which contributed to the deployment challenges encountered at the different surf spots.