Coastal forest protects the shoreline from erosion and extreme events by attenuating wave and velocity by obstructing the flow of water through the forest. Lack of understanding on tree drag coefficients vary with tree morphology density and arrangement is a major source of uncertainty that close related to the shoreline belt span. This study evaluates the behavior of velocity flow through the mangrove aerial root system. The analysis process starts with the drag value analysis of stilt roots model and continues by analyzing the dissipation behavior of velocity on the analysis path. Both analyses were carried out using Computational Fluid Dynamics (CFD) by ANSYS Fluent program. Root zone of the stilt root model is observed contributes higher velocity dissipation than stem zone. The highest drag value is observed at the average of 32.75% of the stilt root height. Higher density of forest stands contribute to higher dissipation of velocity. The study recommends the minimum span 200 m of shoreline forest belt to allow the ecosystem to be shoreline protector naturally. Therefore this study recommend for artificial protector for mangrove seedlings in the early growth. The results are useful for forest managers to restore mangroves and support the establishment of mangrove seedlings for coastal risk reduction strategies.