Dune erosion : product 1: deterministic dune erosion prediction methods

The dune erosion prediction method presently used to assess the safety level of dunes along the Dutch coast was developed for situations with wave periods up to Tp = 12 seconds, while situations can be expected with wave periods larger than Tp = 12 seconds. Preliminary analyses of the potential influence of longer wave periods on dune erosion indicate that larger wave periods lead to more dune erosion. However, effects of the wave period are not quantified sufficiently yet. To allow for the five yearly safety assessment of the Dutch primary water defences the current safety assessment method needs to be extended. With this new method it should be possible to calculate dune erosion under normative hydraulic conditions taking effects of the wave period into account. The present report describes the first phase of this development. The objective of this part of the study is to develop a deterministic dune erosion prediction method based on existing data and existing knowledge on effects of the wave period. All methods in this report have the current method as a starting point. Therefore, they should be considered as an extension of the present set of equations; no entirely new concepts are developed. The new formulations are derived on the basis of a limited amount of data on the effect of the wave period, mainly obtained from small-scale model tests. The formulations should be calibrated by including the results of the large-scale dune erosion tests to be carried out in a later stage of this dune erosion project.