Wave energy dissipation through a hollow triangle breakwater on the coastal Mekong Delta

The Vietnamese Mekong Delta (VMD) has suffered from a number of significant environmental issues, including coastline erosion. This study introduces a new structure of Hollow Triangle Breakwaters (HTB) to protect the coastline, stimulate sedimentation and restore mangrove forests along the Mekong Delta coastline. The hydraulic parameters of the HTB were studied and tested on physical models. These experiments included changing a range of parameters including the porosity of the surface, wave parameters and water level to determine the optimal porosity (KH2) for wave transmission, reflection and wave dissipation. The results showed that the reflection coefficient is inversely proportional to the breakwater porosity screen. The transmission coefficient for a non-overtopped breakwater depends on the breakwater porosity screen on both sides of the HTB. The coefficient of wave energy dissipation is highest when the porosity on the seaside is larger than on the shoreside of the breakwater, particularly in the optimal porosity case (KH2). It is recommended to design the HTB breakwater working under the emerged state (Rc/Hm0, i > 0.5) for the best wave reduction efficiency. The study also compared hydraulic parameters of different types of breakwaters with different shapes and it was found that the porous structures significantly affected the wave transmission coefficient, reflected and dissipation coefficients. The comparison between field measurement and experiment results declares that the HTB structure is able to transmit the long wave passing through the breakwater at a certain level, and dissipates most of the shortwave energy. This facilitates the sedimentation and mangroves restoration in the shoreside area which indicates that the HTB has a significant potential to reduce coastline erosion in the VMD. � 2021 Elsevier Ltd