Design Considerations of Artificial Mangrove Embankments for Mitigating Coastal Floods – Adapting to Sea-level Rise and Long-term Subsidence

Abstract. Mangrove plantation belts are expected to act as natural infrastructural buffers against coastal hazards. However, their performance will not endure over time if the platform is not appropriately designed. In fact, despite massive funds dedicated to the rehabilitation of mangrove forests, the long-term survival rates of mangroves are generally low. This paper investigates the function of mangrove embankments in attenuating the amplitudes of ocean tides through a coupled numerical model that reproduces shallow-water wave propagations under the progress of soil consolidation. The developed model is capable of simulating tidal propagation over an artificial embankment, which will inevitably change its ground surface elevation with the passage of time because of sea-level rise, land subsidence, vegetation growth and sediment accretion. A parametric analysis demonstrates that high tides could be effectively mitigated only if the embankment is appropriately designed to maintain an equilibrium state among these multiple influences over the long term. On the other hand, an embankment designed without considering geomorphological transitions will become submerged under the rising sea level, resulting in no significant effect on tidal damping. Therefore, the artificial mangrove embankment must be carefully designed to function not only during the initial stage of its lifetime but also over time, to avoid system failure in the future.