Delos final report

Summary of all results of the Delos (Environmental design of low crested structures) project. Objectives of Delos were (1) to provide an inventory of Low Crested Structures (LCS), (2) analyse LCS hydrodynamic an stability and their effects on morphology (3) investigate impacts of LCS (4) develop methodology for Integrated Coastal Zone Management (5) provide guidelines for the design of LCS. This report is the administative final report. For technical details is referred to the book "Environmental design guidelines for low crested coastal structures" by Burcharth et.al.Delo

Wave basin experiment Delos

Low-Crested stmctures (LCS's) are typically built in shallow water as detached breakwaters for coastal protection purposes. The structures are usually parallel to the shoreline with wave attack almost perpendicular to the structure. However under special enviromnental conditions more oblique waves can occur. Groin systems or breakwaters for harbours where structures are not parallel to shoreline are other examples in which oblique wave attack occur. Numerical models are still too inaccurate to describe the stability phenomenon especially in case of 3D-waves: Therefore numerical models cannot be used in establishment of design formulae. Several 2D laboratory experiments on trunk armour layer stability of LCS's have been performed in wave channels; see e.g. Allrens 1987, Van der Meer 1990/1996, Loveless and Debski 1997. To our knowledge only one 3D test series with long crested waves has been carried out on complete LCS's, see Vidal et al. 1992. These tests were canied out in the wave basin at NRC, Canada, 1991-1992 on a 4.7m long structure exposed to inegular head-on waves. The results showed that in some situations the rear head was prone to damage. Only one structure geometry was tested with cross-sectien slopes 1V:1.5H. The results could therefore only quantify influence of freeboard on the stability tor that specific geometly. The objective of the new LCS stability tests (mainly roundhead but also trunk) was to supplement existing tests in order to identify the influence on rubble stone stability of: 1) Obliquity of short crested waves 2) Wave height and steepness 3) Crest width 4) Preeboard 5) Structure slope The stability tests were canied out in the short-crested wave basin at Aalborg University in Denmark during the summer 2002.Delo