Experimental study of wave transmission comparison for three pontoon floating breakwater types

Floating breakwaters have attracted increasing attention because of their potential to reduce wave transmission. However, experimental comparisons of different floating breakwater geometries under identical test conditions remain limited. This study investigated the wave transmission performance of rectangular, trapezoidal, and stepped pontoon floating breakwaters using Al-Faw Grand Port, Iraq, as a case study. Eleven models were tested in a wave flume, considering three cross-sectional shapes, five drafts, two chain-mooring configurations, and ten regular wave conditions. The wave transmission coefficient (Kt) was evaluated in relation to these parameters. The results show that cross-sectional geometry significantly influenced wave transmission. The stepped S3 model showed significantly lower Kt values than the trapezoidal T3 model with identical structural dimensions and showed comparable wave attenuation to the rectangular R3 model despite its shorter longitudinal dimension. Increasing the draft consistently reduced Kt across the tested models, whereas the effect of mooring configuration had a comparatively smaller and model-dependent influence on Kt. Overall, the stepped configuration showed better wave-transmission performance than the other geometries investigated. The experimental findings provide a comparative dataset for the hydraulic assessment of pontoon floating breakwaters and a systematic experimental framework that may be applied to similar coastal environments.