Wind wave direction impact on the long-shore sediment transport rate, South East Baltic sea coast

The Lithuanian coast of the south eastern part of the Baltic Sea represents a generic type of more or less straight, high-energy (in the Baltic Sea conditions), actively developing coasts that contain a relatively large amount of finer, mobile sediments, are open to predominating wind directions and are exposed to wave activity for a wide range of wave approach directions. The combination of the angular distribution of winds and the geometry of the coast are such that the wave-induced long-shore sediment transport is, in average, to the north over the entire Curonian spit and the mainland coast of Lithuania. Analysis of the field data performed by the G. Žilinskas (2008) from 1976-2007 revealed that the length of accumulative sections has been considerably reduced. Accordingly, the length of the gradually eroding sectors has increased in the end of the 20th century. In this study were analised potential variations in the long-shore sediment transport rate due changes of the wind wave directions. Sediment transport rate is estimated by the energy flux model, also known as the Coastal Engineering Research Centre (CERC) model. The study area covers the entire coast of Lithuania. Entire coast was divided into 90 grids, about 1 km long beach sectors, at the 3 m depth isobaths. Wave directions calculated every 10 degrees. Most intensive long-shore sediment transport from south to the north was induced by waves from South. Changing wave approaching direction to the SW, long-shore sediment transport rate become smaller. Waves from WSW induce long shore sediment transport from opposite direction, from north to south. Westerly waves already induce maximum sediment transport to the south. It should be noticed that wave direction further shifting to the North induces sediment transport to the north again