Abstract
The Japan Organization for Metals and Security (JOGMEC) is committed to develop a technology to quantitatively evaluate the environmental impacts associated with the development of seafloor hydrothermal deposits (e.g., the effects of turbidity plumes and resedimentation). As part of this project, a seafloor disturbance experiment and monitoring survey was conducted in the Okinawa Sea area in January 2017 to determine the impact of turbidity generated by the SUR mining activity. A numerical model (particle tracking model) developed by JOGMEC was used to quantitatively predict the extent and magnitude of these impact during the experiment. In this study, we first set the condition for generation of turbidity based on the monitoring data to the numerical model, and then we examined the ability to simulate a resedimentation thickness and the spatial distribution pattern during the experiment period.
The simulation results using a time-varying flow field estimated from the observation data such as ADCP showed good agreement with the spatial distribution pattern and resedimentation thickness of the monitoring results, suggesting that the model can be used as a prediction tool for environmental impact assessment during the development of seafloor hydrothermal deposits. In addition, the flow field prediction method using the hydrodynamic model is effective and accurate for the preliminary impact prediction especially under the situation where observation data such as current velocimeters are insufficient. The results of this preliminary impact prediction are expected to be utilized as useful information that contributes to the planning of monitoring surveys.
