Longshore Sediment Transport Along the Coast of Ystad Municipality

Abstract: The coast of Ystad municipality has historically been subject to erosion, leading to the loss of recreational areas and near-beach structures, consequently resulting in the implementation of mitigating measures. With the ongoing climate change, erosion is expected to continue. This generates a need for a better understanding of sediment dynamics and sediment transport patterns, in order to further plan for coastal management in Ystad municipality. This thesis focused on obtaining further information about the coast of Ystad municipality through field surveys and modelling of longshore sediment transport. The modelled sediment transport showed an overall eastern transport direction, with some coastal stretches indicating an alternating transport direction, which was confirmed through observations. The greatest transport magnitudes were found along beaches that have historically been subjected to erosion and accumulation. Further, small changes in shoreline orientation had a large impact on both direction and magnitude of the modelled sediment transport. Grain size statistics derived from sediment field samples resulted in a correlation between median grain size, sorting, and beach face slope. The results showed a correlation between eroded beaches and coarser, less sorted sediment and a steeper beach face slope, whereas accumulated beaches were correlated with a finer, more well sorted material and a gentler slope. Nourished beaches were found to affect the correlations negatively, since nourishing both impacts the shape of the beach profile and the distribution of grain sizes. Further recurring field sampling is recommended for broader comprehension of grain size patterns along the coast and how nourishing affects these on a longer timescale.