Abstract: Under global climate change, coastal erosion and storm surge disasters are becoming increasingly severe, highlighting an urgent need to address high costs and ecological damage caused by traditional hard protection structures. Mangroves, as a nature-based solution, have emerged as a research focus due to their remarkable wave attenuation capacity and ecological benefits. This study develops a vegetation-wave coupled numerical model based on the Smoothed Particle Hydrodynamics (SPH) method and the Morison cylinder resistance model for simulating vegetation drag forces. By isolating the root, stem, and canopy structures of mangroves, we quantify their individual and combined contributions to wave energy dissipation, and examine systematically the wave attenuation mechanisms of three representative mangrove species (Avicennia marina, Ceriops tagal, and Rhizophora stylosa) under varying hydrodynamic conditions. The results demonstrate that roots and canopies play a dominant role in wave dissipation, while stems contribute minimally. The total wave attenuation efficiency follows the nonlinear superposition of the three structural components. And, difference in species is also a major factor of wave dissipation due to their morphological and density differences: Rhizophora stylosa performs best in shallow waters; Avicennia marina best in intermediate water depths; Ceriops tagal with a dense root system best in very shallow waters. This study would lay a basis for further study of mangrove-based ecological coastal protection.

Key words: mangroves, wave-dissipation effect, SPH method, numerical simulation, wave attenuation