Systematic Analysis of Alongshore Sediment Transport Patterns under Varying Sea Level Conditions for Evaluating Stability of Coastal Areas in the Microtidal Baltic Sea

Eelsalu, M.; Viigand, K.; Soomere, T., and Parnell, K.E., 2024. Systematic analysis of alongshore sediment transport patterns under varying sea level conditions for evaluating stability of coastal areas in the microtidal Baltic Sea. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 53-57. Charlotte (North Carolina), ISSN 0749-0208. We systematically analyze wave-driven alongshore sediment transport magnitude and directional patterns in the eastern Baltic Sea under varying sea level conditions. Time series of wave properties are replicated using a nested SWAN model with a spatial resolution of 1–3 nautical miles, forced with ERA5 winds at 1 h resolution for the years 1993 to 2021. Wave-driven potential alongshore sediment transport is evaluated using the Coastal Engineering Research Centre approach and linked to the modeled sea level data. We show that 30–40% of the annual sediment transport occurs when the sea level exceeds the 90th percentile. In most of the study area the prevailing wave direction during such sea levels is the same for all situations. The study area contains three structurally different segments in terms of balance and direction of wave-driven sediment transport that host either unidirectional transport, balance of transport created by wave systems from different directions, and segments stabilized by the impact of bi-directional wave systems that are synchronized with sea level.