SWE-Exner model for evaluating the effectiveness of organic coastal defense in trapping mud and absorbing waves

This study proposes a novel technique to reduce erosion at mangrove plantation sites, aiming to enhance the success rate of mangrove plantations through the implementation of organic coastal defense (OCD). This method is evaluated using a comprehensive mathematical model that integrates two-dimensional Shallow Water Equations (SWEs) and Exner equation for the hydrodynamic and the morphodynamic parts, respectively. This integrated model is then solved computationally by applying the Finite Volume Method (FVM) on a staggered grid arrangement. We perform several benchmark tests involving a variety of wave occurrences on a movable bed to validate the developed model's accuracy. In general, the results indicate that OCD is highly effective in trapping mud and absorbing wave energy. Consequently, this structure holds significant potential for development and adaptation to address the mismatch between surface elevation velocity and sea level rise, which currently poses a significant risk to mangrove conservation. • A coupled NSWE-Exner model is used to simulate wave and bed sediment evolution. • The model is solved numerically using FVM and validated with four experimental data. • Wave and bed interaction with organic coastal defense (OCD) is studied numerically. • The zig-zag structure is more efficient in trapping the mud and dampening the wave. • Study case in Mempawah, Indonesia shows that OCD is the most efficient system.