With the enhancement of people’s awareness of environmental protection, more and more marine ecological structures have been developed and studied. Floating breakwaters as offshore floating structures are essential to protect coastal and near-shore areas from strong wave action. This paper proposes a plant ecological floating breakwater (PEFB) in which rigid plants suitable for growing in the sea are grown on the top deck of a box-type floating breakwater. The relevant researches are carried out by a combination of model experiments and numerical simulations in a three-dimensional wave flume. The experimental PEFB is divided into three submerged depth cases, D₁= 2H/3, D₂= 3H/3, and D₃= 4H/3 (H is the thickness of the box-type floating breakwater below the PEFB). The results show that PEFB exhibits better wave attenuation performance in case D₃. Floating breakwater with rigid plants has better wave attenuation performance than without plants.

The study of hydraulic characteristics of water flow affected by blocked sediment is vital to assess discharge capacity in pipes with sediment sand to understand the process of pollutant and fine sand aggregation. The aim of this paper is to study the blocking effect of permeable sediments on non-full flow in circular pipe and to analyze hydraulic characteristics with backwater. Experiments and numerical simulations were performed and the porous media model is used to simulate the flow in permeable blocked sediments. To evaluate the degree of congestion, the backwater ratio β is proposed. The backwater ratio is positively proportional to blocked sediment height and inversely proportional to blocked sediment particle size and flow value. Cross-sectional velocity in the backwater zone decreases significantly and tends to be uniform as backwater ratio increases. Furthermore, the development of secondary flows and velocity distributions influenced by backwater height is discussed. The dimensionless shear velocity in backwater zone shows an exponential decrease as the backwater ratio increases, which greatly increases the possibility of further sediment deposition.