Study on the Risk Assessment for Oil Spill from Wrecks

关于溢油的研究通常集中在海上的石油上，而本研究针对的是沉船溢油。因为有许多船在沉没时舱室里有货油、燃料油或有害有害物质。然而，我们还没有一个框架来评估沉船溢油所带来的风险。在此背景下，本研究项目由以下三个子主题组成。沉船的溢油建模我们开发了一个计算模型来计算三维潮流分布。该模型结合湍流模型自动计算涡流扩散系数。同时，我们采用随机游走的方法来表示石油在水面和水中的分散和扩散，并结合下面描述的模型来估计石油的释放率，我们将其应用于东京都湾假设沉船的石油泄漏。本文建立了海流作用下水下储罐泄油速率的经验模型。该模型是根据在水洞中进行的一系列溢油试验数据建立的。结果表明，该模型能在实验条件范围内估计出合适的流量。风险分析我们研究了沉船风险排序的两个指标。其中一个指标旨在估计对养鱼业的不利影响，另一个指标使用ESI（环境敏感性指数）图。利用这些指标对两起实际沉船事故的风险进行了估计和比较。为了给上述模型或风险分析提供基础信息，我们收集了日本附近海域的沉船信息，并通过GIS将其建立为数据库。

The researches regarding to the oil spill typically focus on the oil on the sea whereas this research addresses on the oil spill from sunken ships. Because there are many ships sinking with cargo oils, fuel oils or hazardous noxious substances in their compartments. However, we don't have framework to estimate the risks posed from the oil spill of sunken ships. Considering the background, this research project is comprised of three sub themes as follows.1. Oil Spill Modeling for WrecksWe developed a calculation model to compute the three-dimensional tidal current distribution. The model computes eddy diffusivities automatically by incorporating turbulence models. Meanwhile, we apply random walk method with a number of particles to express oil dispersion and diffusion on and in the water, Incorporating the model to estimate the oil release rate, described below, we apply them to the oil spill from hypothetical sunken ship set in the Tokyo bay.2. Oil Release Rate ModelingWe developed an empirical model to estimate the oil release rate from submerged tank under sea current. The model is based on the data obtained from series of oil spill experiments conducted with a water tunnel. It is confirmed that the model can estimate appropriate flow rate in the range of the experimental condition.3. Risk AnalysisWe studied two metrics for ranking the risk of sunken ships. One metric intends to estimate the adverse effect against fish culture industry and the other metric uses the ESI (Environmental Sensitivity Index) Map. With these metrics, the risks of two actual wrecks are estimated and compared Furthermore, to provide fundamental information to the above models or the risk analysis, we collect the information of ships sunken in the adjacent waters of Japan and build up them as database through GIS.