Samenvatting

The report is dedicated to the study of the effects of a sand nourishment at the Roggenplaat in the Eastern Scheldt on the local wave climate. The effects are determined as the influence of the sand nourishment on the wave dampening effect of Roggenplaat.
The wave heights over the nourishment have been compared for the situations with and without a nourishment in the reference year (2010) and target year (2035). The situations for comparison were taken on a normal day and during the storm events. In order to conduct the research the wave data as well as the water level data have been collected throughout 2015. This data became the main source for this analysis.
The wave heights have been analysed together with water levels in order to obtain the information on the wave breaking at the tidal flat. Further, wave transformation of the non-breaking waves over Roggenplaat tidal flat has been studied: shoaling and wave dampening due to bed friction. For the storm situation, the wave growth due to wind forces has also been obtained in order to get the wave heights at the shore, since it is the wave height, which are used for wave load calculations on the dike.
The results have shown that although the water depth is a factor in wave height attenuation, the length of the nourishment plays a more important role in the degree to which waves are dampened. Moreover, wave dampening effect of sand the nourishment is not expressed during storm event. The study has shown that shoaling forces are prevailing over wave dampening due to bed friction, and therefore, Roggenplaat doesn’t show its wave dampening effect during storm events.
The recommendations of the report include a statement that if wave dampening effect of sand nourishment is desired during the storm event, it is suggested to use a wider sand nourishment. One of the results of the study has shown that the length of the nourishment is of greater importance in wave dampening effect compared the height of the nourishment and the related water depth.