Session: 12-03-01 Coastal Processes I

Paper Number: 123147

123147 - Reviving Mangrove Ecosystems: Innovations in Wave-Resilient Plantation 

Mangrove restoration initiatives have been adopted across many nations, yet their overall success remains modest. A recurring setback often occurs during the initial stages of the plantation, primarily due to adverse environmental influences. Of particular concern is the vulnerability of young mangrove seedlings to the detrimental effects of high waves. This study presents a series of field surveys conducted in the mangrove forest of Amami Oshima, Japan, during May and December 2019. In order to comprehend the growth dynamics of young mangroves, we conducted mangrove growth experiments, focusing on the growth rate of Kandelia obavata seeds. To investigate the susceptibility of these juvenile mangroves to wave-induced damage and explore protective measures, we conducted a manual wave experiment in the study area. The experiment revealed that one-month-old mangrove plants were significantly affected, bending and submerging when subjected to continuous wave impacts of up to 10 cm in height. In contrast, six-month-old mangroves exhibited resilience and remained unscathed. To address this vulnerability, we designed a portable reef, inspired by conventional rubble-mound breakwaters, to shield young mangrove saplings from the erosive forces of waves. This breakwater concept was designed to dissipate wave energy effectively.

To assess the effectiveness of this protective reef, we employed Computational Fluid Dynamics (CFD) modeling using olaFlow/OpenFOAM. Four distinct breakwater geometries with a similar cross-sectional area were tested under local wave and tidal conditions specific to the Amami mangrove forest. Numerical simulations demonstrated that these breakwaters, characterized by mounds covering an area of approximately 1m², can attenuate wave heights by a notable range of 48-82%. While wave transmission varied depending on the specific breakwater geometry, the results suggest that even a small rubble-mound breakwater could be a viable solution to safeguard young mangrove plants during their early growth stages.

Key Words: Mangrove Restoration, Young Mangrove, Portable Breakwater, Amami Oshima, Japan, OpenFOAM-Olaflow.

Presenting Author: Sindhu Sreeranga National University of Singapore

Presenting Author Biography: Dr. Sindhu Sreeranga’s research focuses on coastal engineering and ecology, specializing in nature-based solutions for sustainable coastal management. With a PhD from the Tokyo Institute of Technology, Japan, her research revolves around the intricate relationship between fluid flow dynamics and coastal ecosystems. Sindhu employs advanced computational tools such as OpenFOAM and OlaFlow, along with high-performance computing, to model complex fluid dynamics. Her passion for the environment drives her active contributions to the field, including her work on blue carbon, mangrove rehabilitation, breakwater design, field surveys, and providing nature-based solutions. Her dedication to preserving and restoring coastal ecosystems for future generations is a guiding force in her research endeavors.

Apart from research, Sindhu enjoys meditations, nature, landscape photography, cooking and playing with her kid.

Authors:

Sindhu Sreeranga National University of Singapore
Jiarui Lei National University of Singapore
Hiroshi Takagi Tokyo Institute of Technology