These included tank facilities, which caused a number of oil spills. In cases that oil spills spread out onto the sea, the damage by such spills might be caused in both the short- and the long-term. To prepare for such oil spill incidents and develop protection measures for them, improvement of predictions of oil advection and diffusion is required. Our goal, therefore, is to develop a simulation method to predict advection and diffusion of oil spilled owing to a tsunami.
In this study, we propose a simulation method for modeling the transport of oil that is spilled as the result of a tsunami. We use a simulation model, OIL-PARI, to examine spilled oil transport on the water surface using a particle tracking method, and another simulation model, STOC, to simulate seawater motion between offshore and coastal zones. To confirm the method, hindcast simulations are applied to the oil spill incidents that occurred in Kesennuma, Sendai, and Ofunato bays following the Great East Japan Earthquake. We then present a discussion of the simulation results and problems arising from the models.
The simulations show that in cases where the oil spill was located in the interior of a bay -i.e., the mouth of the bay was far from the oil spill site- the spilled oil did not flow out of the mouth of the bay as a result of the tsunami, but rather remained within the bay. Spilled oil was moved by wind and other advection forces following the tsunami, and in all cases, movement due to the weak westerly winds that dominated. For example, Kesennuma and Ofunato bays both have a long north to south dimension, so oil spills simulated in the interior parts of these bays were not blown out by the wind. Conversely, in Sendai Bay, oil spilled at mouth of the bay was modeled to flow out into the open ocean.
To fully understand the mechanisms of spilled oil transported as a result of a tsunami, additional studies are necessary. These include: (1) collection of observational data concerning the locations of spilled oil, which can be used to validate simulation results, (2) verification of simulated tsunami current speeds and directions, and (3) estimations of phenomena associated with oil settling and adhesion with soil and/or sand, and relationships between adhesion and mixing energy.
KeyWords: oil spill, tsunami, numerical simulation, particle tracking method, hindcast simulation