Japan Geoscience Union Meeting 2021

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[J] Oral

A (Atmospheric and Hydrospheric Sciences ) » A-CG Complex & General

[A-CG41] Coastal Ecosystems -2. Coral reefs, seagrass and macroalgal beds, and mangroves

Thu. Jun 3, 2021 10:45 AM - 12:15 PM Ch.10 (Zoom Room 10)

convener:Yu Umezawa(Tokyo University of Agriculture and Technology), Toshihiro Miyajima(Marine Biogeochemistry Group, Division of Ocean-Earth System Science, Atmosphere and Ocean Research Institute, The University of Tokyo), Atsushi Watanabe(The ocean policy research institute, The Sasakawa peace foundation), Tomihiko Higuchi(Atmosphere and Ocean Research Institute, The University of Tokyo), Chairperson:Yu Umezawa(Tokyo University of Agriculture and Technology), Toshihiro Miyajima(Marine Biogeochemistry Group, Division of Ocean-Earth System Science, Atmosphere and Ocean Research Institute, The University of Tokyo), Atsushi Watanabe(The ocean policy research institute, The Sasakawa peace foundation), Tomihiko Higuchi(Atmosphere and Ocean Research Institute, The University of Tokyo)

12:00 PM - 12:15 PM

[ACG41-06] Quantification of drag force and material trapping ability of a planted mangrove forest in the Philippines

*Yoshikai Masaya1, Takashi Nakamura1, Dominic Bautista2, Eugene Herrera2, Takuya Okamoto1, Rempei Suwa3, Kazuo Nadaoka1 (1.School of Environment and Society, Tokyo Institute of Technology, 2.Institute of Civil Engineering, University of the Philippines, 3.Forestry Division, Japan International Research Center for Agricultural Sciences)

Keywords:mangrove, drag, trapping, dispersion, blue carbon

Mangrove forest is an important component of blue carbon ecosystem and plays a major role in climate change mitigation. The complex structures in mangroves’ above-ground roots greatly attenuate flow and trap suspended materials on their surface which promote organic matter deposition in mangrove areas. This study aims to quantify the mangrove drag force and material trapping ability in a planted mangrove forest (Bakhawan Ecopark) in Panay Island, the Philippines. Field measurement was conducted in mono-specific stands of 17-year old Rhizophora apiculata. A precise measurement of water surface slope and velocity profiling were done to quantify the mangrove drag force from the momentum balance. We also measured the projected area of the above-ground roots of R. apiculata stands to estimate the value of drag coefficient (CD). For quantification of the material trapping ability, trapping of floating mangrove leaf litter was monitored by a video camera. The results showed that the drag force by mangroves is much higher (around ten times) than the bed shear stress. While the estimated CD values were close to those measured in other laboratory studies, the data suggested a water depth dependence of CD which may be attributed to the vertical variations in the above-ground root projected area. Similarly, significant changes in the leaf litter dispersal patterns and the trapping efficiency with changing water depth were observed. The results may provide the first estimates of a set of field-derived drag coefficient, dispersion, and trapping ability of a planted mangrove forest.