Understanding the dissipation effect of mangroves is essential for assessing the performance of mangrove forests in mitigating damages from storm surges. In this study, a novel local-drag-force-based approach is proposed for simulating wave propagation through mangrove forests using a 3D-SPH numerical model. In the proposed model, the mangrove forest is represented as emergent rigid cylinders. The dissipation effect of each individual mangrove is defined by the local drag force, which is smoothly distributed around each individual mangrove based on SPH kernel function. The proposed model allows for the consideration of mangrove distribution without the need to simulate flow around each mangrove individually. The proposed model is validated using laboratory wave flume experiment results. The wave-damping coefficient β exhibits a linear relationship with the mangrove total longitudinal cross-sectional area A. The presence of an open channel within mangrove patch weakens the wave-attenuation ability due to the decrease in A. The wave-driven flow field shows that the horizontal flow velocity is greater along the open channel, signifying that the effect of mangrove distribution is considered in the proposed model, e.g. the effect of the open channel is simulated. The obtained numerical results show promising potential of the proposed model to investigate the wave dissipation by mangrove forests and corresponding 3D flow field.