Experimental Investigation of Shoreface Nourishment Scenarios

Sand nourishment is often used as coastal protection as it has fewer negative side effects compared to hard structures. When positioned at the shoreface, the nourishment can protect the beach by acting as a feeder mechanism, but also force waves to break earlier thereby reducing the amount of wave energy that reaches the beach (the sheltering effect). There have been many field measurements on the effect of shoreface nourishments (see e.g. van Duin et al, 2004). These have provided valuable insights, but are very case specific, and there are still very few detailed experimental nourishment studies performed in controlled environments (see e.g. Walstra et al., 2010 and Grasso et al., 2011). The few experimental studies make it difficult to formulate clear nourishment strategies, and there are e.g. different opinions on where in the cross-shore profile the nourished sand should be positioned. van Rijn et al (2011) stated that a nourishment is most efficient when placed landwards of the innermost bar crest and that the bar trough should always be filled, which supported the laboratory results from Walstra et al. (2010). However, the experiments by Grasso et al (2011) showed little difference between nourishing the crest or the trough. In this study we add to this debate and investigate the influence of nourishment spatial positioning as well as the influence of the temporal positioning, i.e. the timing of the nourishment with respect to the “equilibrium”.