2020 Fiscal Year Research-status Report
Quantitative Evaluation of Coastal Forests on Natural Disaster Mitigation - Considering the Complexity of Vegetation Structures
| Project/Area Number |
20K14838
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| Research Institution | Kyoto University |
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Principal Investigator |
張 哲維 京都大学, 防災研究所, 特定助教 (20866826)
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | 海岸林 / 波浪減衰 / 沿岸災害 / 気候変動適応策 / 津波 / 高潮 / 高波 / Eco-DRR |
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| Outline of Annual Research Achievements |
The main objective of this research is to evaluate the protective function of coastal forests against natural disasters. Considering two main types of coastal vegetation in Asia-Pacific areas, i.e. mangroves and pine trees, this research aims to develop a numerical model and quantify the effectiveness of coastal forests on wave attenuation with consideration of vegetation structural complexity.
In this year, a Boussinesq-type model was developed to simulate wave propagation and hydrodynamics in mangrove forests. The vegetation effect was incorporated by the Morison-type formula as addition resistance in the numerical model. Different from the previous studies which required calibration to determine wave dissipation, the drag/inertia force coefficients were directly computed by the empirical formulas obtained from the laboratory experiments for wave forces on 3D-printed mangrove models. The structural characteristics of mangrove roots were also parameterized in the numerical simulation. The numerical results were preliminarily validated by the experimental data. In addition to the development of the numerical model, a field survey was conducted in Iriomote island to investigate the structural characteristics of mangroves. The detailed root structures were captured by a 3D laser scanner and the representative parameters of root morphology were manually measured. By collecting the variety of vegetation structures in fields, a more comprehensive parameterization of mangrove root morphology can be developed for future model application to more realistic scenarios.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The numerical model has been developed and tested using experimental results for a specific type of mangrove. The results were published in the Journal of Japan Society of Civil Engineers (Coastal Engineering). A field survey was also conducted in Iriomote island to investigate the structural characteristics of mangroves, which will facilitate the establishment of the parameter base for the numerical model. The laboratory experiments and more numerical tests will be conducted based on the field data. What has been accomplished meets the first-stage objectives as planned.
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| Strategy for Future Research Activity |
To generalize the numerical model, a more comprehensive dataset of vegetation morphology, including the representative geometrical characteristics and the detailed structures of vegetation, will be required from field inputs. Besides, laboratory tests resembling field conditions are needed to not only observe the physical processes but also validate the simulated results. Accordingly, several steps will be carried out at the next stage.
(1) The collected dataset of mangrove root morphology in Iriomote island and its parameterization in the numerical model will be further analyzed.
(2) Field surveys will be conducted to investigate the characteristics of pine trees.
(3) A series of laboratory experiments with different configurations will be conducted to investigate vegetation-induced resistance and the associated wave attenuation. Various incident wave conditions will also be tested to simulate tsunamis, storm surges and waves.
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| Causes of Carryover |
The Covid-19 makes it impossible to conduct the field studies as initially planned, and several conferences were held virtually, reducing the overall traveling expense.
Accordingly, I slightly adjusted the schedule of this research and started to develop the numerical model in the first year. The laboratory experiments and field surveys are planned for FY2021. The remaining budget for FY2020 and the fund granted for FY2021 will be used for laboratory experiments (e.g. the purchase of experimental equipment and 3D printer filament) and field surveys. Data storage will also be purchased for the use of numerical simulation.
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