C.O. van IJzendoorn1*, S. de Vries, C. Hallin1 2
2 Lund University
The decadal development of coastal dunes is a result of the interplay between marine and aeolian processes. To date, it is unclear how this development is governed by short-term processes like storms and long term processes like sea level rise. Previous researches, have studied the decadal dune behavior by looking at one or two specific geomorphological parameters. For instance, Ruessink and Jeuken (2002) used the cross-shore dune foot location and De Vries et al. (2012) used dune volume and beach slope. Here, we identify decadal trends in profile shape along the Dutch coast with an emphasis on the dune foot and crest level. These parameters are expected to increase in elevation with sea level rise.
In this study, the extensive JarKus database is used. The dataset contains 200-250 m spaced profiles that have been measured yearly since 1965. In all transects the locations of important geometric features are identified. This allows for quantification and analysis of the development of the coastal profile. Figure 1 shows an example of the dune crest and dune foot in a coastal profile.
Figure 1 The definition of important geometric features in a coastal profile from the Jarkus dataset.
Results and discussion
The analysis of the Jarkus dataset results in the identification of several long term trends. It is found that when averaging the total dataset, the dune foot elevation increases linearly by 6 mm per year (Figure 2). The dune foot also moves ±1.5 m seaward per year. However, this trend is not linear and shows a clear break around 1990, which could be related to increased nourishments. Additionally, it is found that the dune crest elevation along the Dutch coast increases 4 cm per year (Figure 2). A vertical translation of the coastal profile with sea level rise can be expected based on traditional concepts (e.g. by Bruun). However, the derived dune foot and crest positions show a much larger rise than expected based on sea level rise only (Figure 3). Governing processes for this averaged behaviour remain unclear. A more detailed analysis of specific locations (e.g. nourished areas) might unravel specific governing processes.
Figure 2 Dune foot and crest elevation through time
Figure 3 Sea level along the Dutch coast
- Ruessink, B.G., Jeuken, M.C.J.L. (2002). Dunefoot dynamics along the Dutch coast. Earth Surface Processes and Landforms 27 (10), pp. 1043-1056.
- De Vries, Southgate, Kanning, Ranasinghe (2012). Dune behaviour and aeolian transport on decadal timescales, Coastal engineering, 67, pp. 41-53.