Foredune growth and storm surge protection potential at the Eiderstedt Peninsula, Germany

Abstract

In the context of climate change and associated sea level rise, coastal dunes can provide an essential contribution to coastal protection against wave attack and flooding. Since dunes are highly dynamic systems, their potential safety levels are related to their long-term development, varying in time and space, however pertinent research that ties those aspects together are generally scarce. The objective of this study is to analyze the long-term development of a young coastal foredune at the Eiderstedt peninsula, Germany and assess its coastal protection potential. This research presents (i) a novel semi-automated Dune Toe Tracking (DTT) method to systematically extract dune toes from cross-shore elevation profiles; (ii) established tools to derive the extraction of characteristic dune parameters and (iii) a newly defined Critical Storm Surge Level (CSSL) to relate spatio-temporal dune growth with coastal storm surge protection. Based on geospatial survey data, initial dune formation was identified in the 1980s. By 2015, the foredune had developed over a 6.5 km coastal stretch with a mean annual growth of 7.4m³/m. During the course of dune evolution, the seaward dune toe shifted seaward by an average of 2.3m/yr, while simultaneously increasing in height by an average of 1.1 cm/yr. Overall, the foredune formation established a new line of defense in front of an existing dike/dune line that provides spatially varying protection against a mean CSSL of 3.4m + NHN and can serve as an additional buffer against wave attack during severe storm events.

Dune toe dynamics along the urbanised macro‐tidal coast of Belgium

“…Mehrtens et al (2023) and van IJzendoorn et al (2021) demonstrated a similar seaward movement of the shoreline, like this study, of 2.3 m/…”

“…This is comparable to the results of this study suggesting that the dune toe is rising at a similar rate along both the Dutch and Belgian coasts. Furthermore, a recent study of Mehrtens et al (2023) also has found that the seaward dune toe elevation along the west coast of the Eiderstedt peninsula in Germany increases by 1.1 cm/year over the period from 1984 to 2015. This suggests that dune toe elevation may be rising at a similar rate along various coastal regions in western Europe.…”

“…In this study, we utilised a derivative method to detect the position of However, the method may not provide good approximations for dune toe position in areas where management works, such as the creation of beach plateaus for touristic exploitation or the presence of natural beach scarps, resulting in anomalies that cause a clear break in beach slope that may not indicate the actual dune toe (third panel of Figure 8 and Figure 7) as also pointed out by Diamantidou et al (2020). In order to counteract these anomalies, different cross-shore intervals could be used to evaluate dune toe positions (Mehrtens et al, 2023). This makes the performance of the derivative method largely dependent on the spatial resolution of the dataset used.…”

“…Yet, this sediment budget does not provide information on how the sediment is distributed within the dune profile and how human activities alter these dune profiles, as it mostly reflects a volume confined by fixed or static boundaries determined by convention or geometric patterns (Bochev-van der Burgh et al, 2011;Ruessink & Jeuken, 2002;Strypsteen, Houthuys, & Rauwoens, 2019). The majority of the Belgian coastal dunes experience decadal volume growth with an average rate of 6.2 m 3 /m/year and maximum rates of 12.3 m 3 /m/year, which is positively correlated with the aeolian sediment transport from the beach area under dominant southwesterly and westerly winds (Strypsteen, Houthuys, & Rauwoens, 2019) The dune toe, defined as the line separating the beach from the dune, serves as a proxy for shoreline position, and its position is subject to variation on both temporal and spatial scales (Bochev-van der Burgh et al, 2011;Diamantidou et al, 2020;Mehrtens et al, 2023;Ruessink & Jeuken, 2002;van IJzendoorn et al, 2021). Determining the location of the dune toe can be challenging as there is not one consistent and generic definition but several based on the crowdsourced study of Smith et al (2020).…”

Design and Insights Gained in a Real-World Laboratory for the Implementation of New Coastal Protection Strategies

“…simply compensate for the anticipated loss of biodiversity [7]. A promising approach to promote coastal resilience are nature-based solutions (NbS) that offer or even exploit services provided by ecosystems [8,9], e.g., wave attenuation [10,11], accretion of sediments or reduction of erosion naturally provisioned or supported by coral reefs, salt marshes, seagrass meadows or coastal dunes [12][13][14][15][16]. Further studies and experiences of NbS are provided and discussed, e.g., by Scheres et al [17] on alternative plant coverage and its root systems stabilizing sea dikes or by Staudt et al [18] on the ecological dimensions of beach and foreshore nourishments with marine aggregates, such as sand and gravel.…”