Controls on coastal flooding in the southern Baltic Sea revealed from the late Holocene sedimentary records

Abstract

Climate change and related sea-level rise pose significant threats to lowland coasts. However, the role of key controlling factors responsible for the frequency and landward extent of extreme storm surges is not yet fully understood. Here, we present a high-resolution sedimentary record of extreme storm surge flooding from the non-tidal southern Baltic Sea, spanning two periods: 3.6–2.9 ka BP and 0.7 ka BP until present. Sediments from coastal wetland, including sandy event layers, were analyzed by sedimentological (grain size, loss-on-ignition, micromorphology), geochronological (14C), geochemical (XRF), mineralogical (heavy minerals) and micropaleontological (diatoms) methods. The results show that both periods were characterized by high-frequency of storm surge flooding, in order of 1.3–4.2 events per century. These periods correlate with phases of enhanced storminess in northwest Europe and took place during both rising and fluctuating sea levels. The study shows that the frequency and landward extent of coastal inundation, largely depended on the development of natural barriers (e.g. beach ridges and aeolian foredunes). Thus, in the context of the future coastal storm-surge hazard, the protection of existing coastal barriers and their morphology is essential.

A 1500‐year record of North Atlantic storm flooding from lacustrine sediments, Shetland Islands (UK)

“…Changing boundary conditions such as tides, fetch, season, etc., additionally influence the occurrence of overwash (Liu and Fearn, 2000; Liu, 2004; Moskalewicz et al, 2020). Also, the stage of coastal landform development has to be considered (Leszczyńska et al, 2022). Any estimation of the number of storm events from individual sand layers should therefore be treated with caution (Biguenet et al, 2021).…”

“…To assess whether storm activity has increased in north‐western Europe and to catch high‐magnitude and low‐probability events, high‐resolution records of past North Atlantic storm flooding over timescales longer than the instrumental record are required (Clarke and Rendell, 2009; May et al, 2013; Goslin and Clemmensen, 2017; Moskalewicz et al, 2020; Leszczyńska et al, 2022). These records may be extended by the use of proxy data from sedimentary archives that reflect specific aspects of storm flooding at centennial to millennial timescales, for example from coastal lakes (Liu, 2004; May et al, 2013).…”

Late Holocene Vistula River Floods Recorded in Grain Size Distributions and Diatom Assemblages of Marine Sediments of the Gulf of Gdańsk (Baltic Sea)

“…The changes in the mean grain size, as discussed in the previous chapters, reflect the distance from the major source and the effectiveness of sediment redistribution due to waves, currents, etc. Thus, one may expect that the coarsest sediments could be related to major storm events (Moskalewicz et al, 2020;Leszczyńska et al, 2022). Indeed, the coarsest mean grain size was noted in GC10 core (Fig.…”

“…The latter resulted in decreased accumulation within the inner delta plain and an establishment of a new sedimentary depocentre in the Gulf of Gdańsk. Although, many studies on various aspects of environmental changes recorded in the Gulf of Gdańsk sediments have been carried out (e.g., Sternbeck et al, 2000;Uścinowicz, 2003;Dippner and Voss, 2004;Witak, 2010;Szymczak-Żyła and Kowalewska, 2009;Szymczak-Żyła et al, 2017Szymczak-Żyła et al, , 2019Uścinowicz et al, 2022), and recent flood (e.g., the largest during the last 130 years Vistula River flood in the 2010) or storm events (Zajączkowski et al, 2010;Moskalewicz et al, 2020;Leszczyńska et al, 2022) proved the potential importance of these processes in the Gulf of Gdańsk, the studies focused on long-term sedimentary flood records are missing, so far. These geological records are potentially important in the context of ongoing climate change and related variations in the frequency and magnitude of extreme events, as they may provide the testing ground for climate models.…”

Regional assessment of extreme sea levels and associated coastal flooding along the German Baltic Sea coast

“…the peak water level), the duration of the surge (particularly in microtidal environments such as the Baltic Sea), and wave setup (Höffken et al, 2020;Hendry et al, 2019). Topographic datasets constitute a major source of uncertainty in large-scale coastal flood modelling, particularly because natural and anthropogenic flood barriers such as dikes are often not sufficiently well resolved (Leszczyńska et al, 2022;Vousdoukas et al, 2018). Problematically, disregarding human adaptation constitutes the largest bias in regional-to global-scale flood risk assessments, and data availability is often a major concern (Hinkel et al, 2021).…”