Coastal erosion has intensified under the increasing frequency of extreme weather and climate events, posing significant threats to coastal communities and ecosystems. In Thailand, with more than 3,000 kilometers of coastline along the Gulf of Thailand and the Andaman Sea, erosion is driven by monsoonal waves, storm surges, and human activities that alter sediment transport. Conventional hard-engineering structures such as seawalls and breakwaters often lead to ecological damage and aggravate erosion in adjacent areas. This study investigates two nature-based green structures—artificial oyster reefs (AORs) and artificial seadomes—as sustainable approaches for mitigating coastal erosion and enhancing habitat resilience.

The first part of the study focuses on an experimental investigation of artificial oyster reefs designed to dissipate wave energy and reduce shoreline erosion. Laboratory flume tests were conducted using a 1:10 scale physical model to analyze wave behavior and energy dissipation across various reef configurations. Dimensional analysis and similarity principles were applied to ensure accurate representation of field conditions. The study evaluated wave attenuation efficiency and transmission coefficients to identify effective arrangements for coastal protection.

The second part presents a numerical study of artificial seadomes for coastal defense applications. Forty simulation scenarios were carried out using 3D computational fluid dynamics (CFD) with the RNG k–ε turbulence model to examine hydrodynamic responses under different water depths (h), incident wave heights (Hi), and wavelengths (L). The results indicate that a relative structure height (D/h) greater than 1.0 and a relative wavelength (L/Be) between 0.5 and 1.0 can reduce wave amplitudes by over 90%, with optimal dome widths (45–60 cm) achieving reductions up to 98%. A nomogram was developed as a design tool for optimizing seadome placement.

These findings demonstrate the potential of nature-based green structures as environmentally friendly alternatives for coastal erosion protection.