Large-scale investigation of wave dampening characteristics of organic, artificial floating islands

Abstract

The concept of floating vegetation-based islands for the bioremediation of aquatic ecosystems is well known. Less so, their hydrodynamic capabilities regarding the damping performance, positional stability and water-structure interactions. To this end, physical model tests with fully organic, reed-based gabions were carried out in a large-scale facility in this study. The initial, reflected, and transmitted waves were recorded and analyzed regarding transmission and reflection coefficients. A motion tracking system was utilized to allow for an investigation regarding the motion of the artificial floating islands under waves. The results show that the artificial floating islands significantly dampen shorter waves with a wave period of T ≤ 2.25 s. The transmission of the incident waves is reduced by 50% for the smallest wave periods (T = 1.5 s). The incident waves are reflected between 20 and 50% for the same wave period. The incident wave energy is dissipated by up to 85% for the smallest wave height and period (H = 0.10 m, T = 1.5 s). The comparable performance regarding more traditional floating breakwaters is discussed as well as the width of the structure as the key parameter for the layout of artificial floating islands in rivers and still waters regarding the damping performance.