The structure was designed as a homogeneous rubble mound
and built of quarried rock with a 1 V:1.5H seaward slope. The stones
were placed in gabion baskets along the shoreward slope to
improve the structural stability and reduce the amount of required
stones (Fig. 3). The other advantage of using gabion basket is that
smaller stones could be used to fill the baskets. Although basket
wire can deteriorate after several years affecting the structure
stability, during this period, planted mangroves will develop suitable
protection along the shoreline, so that as mangroves grow up
the importance of the breakwater’s function decreases. Displacement
and removal of stones from the armour layer by wave attacks
and settlement of the structure due to removal of fine particles of
base materials are considered as main failure mechanisms.
Crest elevation assessment is amongst the most important
parameters in breakwater design which has a significant effect on
both hydraulic stability of the structure and the breakwater’s
function (Dean et al., 1997). A higher crest elevation results in
a lower wave transmission, but it increases the amount of required
materials (the construction costs). Moreover, smaller armour
stones can be used on the seaward slope of a low crested structure
(compared to emerged structures) as wave energy can partly pass
over the crest (Van der Meer and Pilarczyk, 1990). On the basis of
a desk study, an optimum crest level was selected providing
a transmission coefficient of about 0.4 under typical storm conditions
at mean high water