WAVE TRANSMISSION AND DISSIPATION BY HYBRID (VEGETATED WITH MANGROVE) BREAKWATERS

Abstract

In recent years a group of studies for coastal protection (Hashim and Catherine (2013), Maza et al. (2018), Tomiczek et al. (2020), among others) have been carried out to determine drag coefficients in mangrove forests due to ocean waves. Following the mangrove hybrid platform concept by Tagaki (2019), and actual projects such as the mangrove rehabilitation site in the Jakarta Fishing Port, the main objective of this study was to propose and test a hybrid structure capable of controlling wave energy via breaking and dissipation. The experimental tests focused on determining the rates of the wave energy distribution (reflection, transmission and dissipation) due to the presence of an afforested mangrove zone in the upper part of the breakwater. A fixed-bottom small-scale model was tested under normal and extreme marine regimes. The prototype dimensions of the breakwater are total height 5.70 m, crest width 10 m, seaside slope 2:1 (H:V) and leeward slope (1.5:1). The barrier is composed of a rigid bottom built of artificial elements (cubipods) and a long crown intended to be vegetated (with red mangroves, for example). The rationale behind this configuration is to provide ecosystem services by an artificially built mangrove forest protected by the rigid bottom. The experimental program consisted of 54 experiments divided into 7 groups corresponding to regular and irregular waves, mean and extreme and high and low tide conditions. Other variables of interest were the density and spatial distribution of mangroves, such as core materials.