Experimental analysis of piling-up and filtration in presence of low crested structures

In the recent years, interest in Low Crested Structures (LCSs) has been growing up together with the sensitivity to environmental impacts produced by coastal defences. Both a national PRIN 2001 and EC project DELOS allowed to achieve a deeper knowledge of such structure type. Overtopping however, which is a crucial aspect of LCSs, has not been completely characterised yet. The aim of this contribution is to experimentally analyse in a wave flume, equipped with a recirculation system, the filtration discharge (and thus the overtopping) in presence of permeable LCSs, characterised by different submergence, berm slope and width. Different wave conditions are tested with varying recirculation discharge, till null piling-up is reached. For the limited range of tested waves, results obtained so far show that overtopping is roughly proportional to piling-up in confined conditions (absence of filtration), and piling-up is proportional to filtration. The comparison of available piling-up dataset with existing formulae show poor agreement.