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Ernstsen, V.B., Lefebvre, A., Kroon, A. and Niemann, S.L., 2013. Oblique second-order sand transport patterns on an intertidal sand flat in a natural tidal inlet system. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.) A detailed digital elevation model (DEM) of an intertidal sand flat in the Knudedyb tidal inlet in the Danish Wadden Sea, derived from high-resolution Light Detection And Ranging (LiDAR) data, reveals a large elongated bedform field with complex bedform morphologies and drainage channel networks. This indicates distinct second-order sand transport pathways oblique to the main tidal transport pathways. A conceptual model for the development of the bedforms and channels is presented, which comprises hypotheses of the hydrodynamic forcing of the different second-order sand transport pathways. During flood tide, sand is transported along ESE-oriented pathways across the intertidal flat towards the inner tidal basin. During the late stages of ebb tide, sand is tran...

This paper uses results obtained from the large-scale BARDEX II experiment undertaken in the Delta flume to investigate the morphological response of a prototype sandy barrier to wave and tidal forcing during overwash conditions. Since overwash processes are known to control short-term barrier dynamics and long-term barrier migration, the development of a robust quantitative method to define the critical conditions leading to barrier overwash is important both for scientific and practical management purposes. The Overwash Potential (OP), defined as the difference between the wave runup and the barrier elevation is used to define the overwash threshold condition, and to predict the morphological outcome of a particular overwash event. When OP is negative, wave runup is lower than the barrier crest and insignificant morphological changes are noticed at the barrier crest. When OP is positive, overwash occurs because predicted runup elevation is higher than the barrier crest. When OP is close to zero, overtop is expected with limited intrusion of water across the top of the barrier crest. To make effective use of OP it is necessary to identify a reliable runup predictor. Twelve runup equations were tested for this purpose, and the results were compared with the ones obtained using data from BARDEX experiment on a gravel barrier. A most reliable approach for the determination of OP for sandy barrier was similar to gravel barrier overwash experiments, with runup predictions provided by the equation of Stockdon et al. [Stockdon, H.F., Holman, R.A., Howd, P.A.,Sallenger, A.H., 2006. Empirical parameterization of setup, swash, and runup. Coast. Eng., 53, 573-588]. This is striking, since different runup predictors would have been expected because beach slope, hydraulic conductivity, grain-size, amongst other factors, differ for both types of barriers. Nevertheless, the two main morphologic characteristics for the computation of OP are beach slope and the barrier crest elevation, both accounted for in the proposed equation. The use of OP values provides a practical means by which to identify potential coastal hazards associated with barrier overwash processes and is considered to have a range of practical coastal management applications. Delta flume BARDEX II project (HYDRALAB IV, contract no. 261520, Barrier Dynamics Experiment). RUSH project (From Runup to Overwash), PTDC/CTE-GIX/116814/2010 financed by FCT. info:eu-repo/semantics/publishedVersion

Kroon, A., Kabuth, A.K. and Westh, S., 2013. Morphologic evolution of a storm surge barrier system. Morphologic evolution of a barrier island system on the southern shore of Zealand, Denmark shows regular inlet breaching and inlet closing over the last centuries. At the same time, the barrier slowly moves in a landward direction at its most exposed stretches. Alongshore wave-driven processes cause shoreline alignment and closure of inlets. A combination of high-energy waves and high water levels induces inlet breaching and overwash processes over the barrier crests. However, local high water levels are often not correlated with storm events in the inner Danish coastal waters. The water level fluctuations along the southern shore of Zealand are strongly influenced by the water level fluctuations in the Kattegat due to wind set-up and seiches in the Baltic Sea; local wind set-up and local wave set-up on the southern shore of Zealand are often of secondary importance. Statistics on extreme water lev...

Kabuth, A.K.; Kroon, A., and Pedersen, J.B.T., 2014. Multidecadal shoreline changes in Denmark. Multidecadal shoreline changes along ca. 7000 km coastline around Denmark were computed for the time interval between 1862 AD and 2005 AD and were connected with a geomorphological coastal classification. The shoreline data set was based on shoreline positions from historical and modern topographic maps. Coastal landforms were identified on a digital terrain model in combination with aerial photographs. Two shoreline-change computation methods were evaluated at a test site, aiming for optimized time efficiency and accuracy of the countrywide application: a Nearest Neighbor search and a cross-shore transect method based on the ArcGIS-based Digital Shoreline Analysis System (DSAS). The cross-shore transect method was more robust and performed better in the detection of local extremes in shoreline changes, which was crucial for the scope of the mapping. Countrywide shoreline-change distances and rates wer...