OPTIMUM GEOMETRY FOR NATURALLY ARMORING BERM BREAKWATERS

A naturally armoring berm breakwater (NABB), as the name implies, is a breakwater that is built with a berm on the seaward side and derives its stability through a mechanism called ''natural armoring''. A serie s of two and three dimensional hydraulic model tests was undertaken at the Coastal Engineering Research Laboratory of Queen's University (QU CERL), Kingston, Ontario, Canada to evaluate the factors affecting the stability of NABB. The parameters that were varied in the tests inclu ded the significant wave height (H-s), wave period (Tp), lower front s lope (LFS), initial berm width (Bi), number of waves (N) and the volum e of material placed in the berm (V). In all tests, the characteristic s of the material were held constant in order to systematically evalua te the influence of the factors mentioned above. The influence of the lower front slope of the berm on the stability and profile formation i n a NABB forms the basis of this paper. Overall, the study showed that the stability of the trunk of a NABB is influenced by the wave height , wave period and lower front slope. A breakwater section having a low er front slope equal to the natural angle of repose was found breakwat er.