Investigation on flow hydrodynamics and structural impacts in the built environment protected by idealized mangrove Forest: Experimental and numerical approaches

Abstract

This study investigates the effectiveness of green and gray mitigation measures in protecting coastal communities from tsunami-driven flooding using Computational Fluid Dynamics (CFD) simulations in OpenFOAM, validated against 1/16 scaled physical experiments. Strong agreement was observed between measured and simulated free surface displacement and horizontal forces. The analysis highlights that increasing the cross-shore width of mangrove forests enhances velocity dissipation, though its effect on maximum wave height reduction is limited. While gray structures—seawalls (SW), submerged breakwaters (SB), and their combination (SWSB)—were more effective in reducing inundation depths, mangroves significantly attenuated flow velocity. Buildings with full mangrove protection experienced reduced wave runup heights and pressures, whereas partial protection led to increased runup due to edge effects. Notably, an eight-row mangrove forest achieved similar load reductions over the first five building rows as the SWSB configuration. Additionally, an empirical equation was developed to quantify the relationship between force reduction and mangrove width. These findings provide critical insights for coastal resilience planning, demonstrating that while gray structures excel at reducing inundation, mangrove forests offer substantial velocity mitigation, emphasizing their role in sustainable coastal defense strategies. © 2025 Elsevier Ltd