Nearshore Currents in Southeastern Scania

Abstract: The South East Coast of Scania is a popular destination for both Swedish and foreign tourists. The long and wide sandy beaches are well visited by swimmers and beachgoers, but the waters have shown to be treacherous at times. In Au- gust 2015, two German tourists drowned after getting caught in a probable rip current in the proximity of Hav ̈ang beach. Six months after the accident, this thesis study, which aims to investigate the nearshore currents in the region was initiated. The main objective was to map the currents prevalent in the area, with special attention to the offshore directed rip currents. In order to accomplish this, GPS-equipped drifters were developed for in-field measurements. The field work includes both drifter measurements and grain size sampling. Data of the local bathymetry from the project Sk ̊anestrand was studied and a bathy- metric survey was conducted. The study also includes offshore wave hindcasting and modeling of the wave transformation as waves approach shore. Drifter measurements were conducted on four beaches at varying wave condi- tions. On 17-18 September 2016, rip currents were observed at Vitem ̈olla beach. The offshore velocity of the current was found to be 0.4-1 m/s, which resembles velocities found in earlier studies (Winter et al. (2011), Dalrymple et al. (2011), Short (1985)). The other field measurements did not register any significant rip currents but rather strong longshore currents. The results from the wave trans- formation EBED model (with hindcasted waves as input) showed that a wave height variation along Vitem ̈olla beach of more than 0.5 m can occur under the similar wave conditions. It was concluded that this could generate enough wave setup variation to drive rip currents. Furthermore, it can be concluded that most of the beaches within the study area are very dynamic, and in order to predict the nearshore currents with models up-to-date bathymetry and more reliable wave data is needed. With field measurements, literature studies and documentation of historical ac- cidents as a basis, a current map for the study area was developed. This study showed that the public should be attentive when swimming in the ocean when the beaches are subject to waves. A simple measure for preventing further accidents would be to red-flag all beaches under such conditions.