Physical and numerical modeling of four different shapes of breakwaters to test the suspended sediment trapping capacity in the Mekong Delta

Extreme coastline erosion has become a major issue in Vietnam's Mekong Delta. Many coastal protection measures have been assessed based on their ability to dissipate incoming waves rather than their ability to facilitate environmental exchange and sedimentation processes. The goal of this study is to evaluate the ability of hollow and porous types of breakwaters to exchange suspended sediment on the deltaic coast. The experiments are set considering the hydrodynamic conditions of the Mekong Delta. We thought of four different types of breakwaters, including pile-rock porous breakwaters (CMD), two-sided perforated hollow breakwaters (TC1 & DRT/VTC), and curtain breakwaters (CWB45). Physical modeling in a wave flume was engaged to investigate the relationship between breakwater shape and sediment-capturing ability. All different breakwaters were placed on the wave flume with identical boundary conditions. Besides the physical modeling in the laboratory, Computational Fluid Dynamics (CFD) techniques using the FLOW3D model were applied. This provided an opportunity to understand the current distribution and the interactions between the fluid and the breakwater, as well as the ability to extract the vertical velocity profile and further additional insights from the interactions of waves and currents with the breakwaters. The wave parameters collected in the lab were further used to evaluate the numerical simulations in FLOW3D, and model validation demonstrated a good agreement with R2 = 0.74–0.98 and NSE = 0.74–0.96 for FLOW3D calibration and validation. It was found that fine sand and mud silt deposition on the shoreline of the breakwater alignment were significantly reduced in the case of the perforated hollow breakwaters. Therefore, using these hollow breakwaters for wave energy dissipation and sediment trapping presents a dual purpose in creating an environmentally friendly solution to recover mudflats. Hollow breakwaters also provide numerous advantages for supporting the creation of favorable conditions for the revival of mangrove forests, development of regional biodiversity, and overall improvement of coastal ecosystems on the deltaic coast. © 2022 Elsevier Ltd