Performance of natural mangrove structure in downstream velocity reduction as compared to engineered porcupine and geobag structure using OpenFOAM

Bank erosion is a regular occurrence along most rivers. In low-income nations such as India and Bangladesh, economical engineered structures such as porcupines and geobags have been used to counteract such erosions. Nonetheless, at times of extreme flooding, these structures often become unstable and are subsequently washed away, thereby failing to protect the banks. Vetiver grass, which ties the soil with its roots, is a natural method for preventing bank erosion. However, its flexible structure is unable to significantly reduce velocity. In this study, the OpenFOAM open-source hydrodynamic model was used to assess the efficacy of mangrove root structure in reducing flow velocity. It has been compared to single screen porcupine, dual screen porcupine, and geobag structure in terms of performance in downstream flow velocity reduction. It was observed that single screen porcupine was the least effective at reducing velocity (0.32 %), followed by dual screen porcupine (3.63 %) and single geobag (5.66 %). On the other hand, the mangrove structure was able to lower downstream velocity by 14.26%. In terms of its downstream influence, the single screen porcupine had its influence upto 3.63 cm, followed by dual screen porcupine with 5.53 cm, and single geobag with 13.03 cm. The mangrove structure influence zone on the other hand was very close to the geobag structure (11.53 cm). With its greater velocity reduction capabilities and a considerable zone of influence, mangrove plantations on riverbanks may therefore function as a cost-effective and ecologically sustainable soil erosion management strategy.