European experience of low crested structures for coastal management

This paper aims to describe selected study sites monitored and analyzed during the DELOS project. All the selected sites are protected by Low Crested Structures (LCSs) under various environmental conditions. In the first part of the paper the characteristics of the European structures are presented and the results of the inventory are summarized with statistical comparison with LCS characteristics in the worldwide scenario (Japan and USA). In the second part a description of the sites and prototype observation of the impact of LCSs is given: a description of the site, environmental conditions and response to its construction based on existing literature and on activities performed during the project are summarized and the research results are reported. Where available observation on ecological impacts and socioeconomic effects are provided. The descriptions are introductory to other DELOS Special Issue papers dealing with prototype observations and experiments. The geometric characteristics of the sites are very wide-ranging: deeply submerged LCSs perform well when groins are present (Pellestrina), whereas for semi-submerged LCSs (Lido di Dante) particular maintenance has to be planned for vulnerable parts, such as gaps and roundheads, where strong currents are responsible for erosion. Emergent LCSs show the formation of salients (Altafulla) or tombolos (Lønstrup) depending on the shoreline distances. In macro-tidal beaches (Elmer) tidal currents can control the salient development and the overall performance of the scheme.