Bas Hoonhout, Kees den Heijer


The dune assessment methods used to ensure the safety of the lower areas in The Netherlands are based on simple empirical relations that are, strictly speaking, only valid for infinitely long, uniform and straight coasts. The wide application of these relations is mainly justified due to intentional overestimation of the expected dune erosion. In context of climate change and expected sea level rise, it is worthwhile to investigate the needs for this overestimation before any physical measures are taken. This paper describes a research to the influence on the dune erosion process of two longshore phenomena that are neglected in these relations so far: coastal curvatures and oblique wave attack. It is shown that the normative retreat distance can increase over 100% for curvatures relevant for The Netherlands. Furthermore, it is shown that the sensitivity of dune erosion models changes when working with curved coastlines. It is also shown that the importance of several model parameters is influenced by coastal curvatures and special attention should be paid to the correlations between storm surge levels and wave parameters.


dune erosion; curved coastlines; reliability; assessment

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