Dynamic Risk Assessment of Shoreline Contamination from Ships: Integrating an Oil Spill Model

Abstract

Latest scientific and technological developments on coastal monitoring and operational oceanography have provided the opportunity of building complex and integrative decision support systems for coastal risk management. An innovative methodology to dynamically produce quantified risks has been developed, integrating numerical metocean forecasts and oil spill simulations with the existing monitoring tools. The risk rating combines the likelihood of an oil spill occurring from a vessel navigating in the study area with the assessed consequences to the shoreline. The spill likelihood is based on dynamic marine weather conditions and statistical information from previous accidents. The shoreline consequences reflect the associated oil amount reaching shoreline and the environmental and socio-economic vulnerabilities. The oil reaching shoreline is quantified with an oil spill fate and behavior model. Shoreline risk is variable in time, based on variable vessel positions (from AIS) and metocean conditions (from operational numerical models). The simultaneous calculation of the risk posed by each vessel crossing a study area is integrated, allowing the generation of a dynamic shoreline risk map for the study area. Shoreline risks can be computed in real time or from previous obtained data. The whole system has been implemented in real time on the Portuguese and Galician Coast. Since several ships cross this area, optimization was performed to allow running the oil spill model for multiple virtual spills from ships along time. The integrated oil spill model uses MOHID lagrangian particle tracking system, where all major transport and weathering processes are considered, including full 3D movement of oil particles, wave-induced currents, and a novel implementation of oil-shoreline interaction. The relevance of integrating the oil spill model in the risk algorithm is evaluated. To perform this, risk levels are compared considering the impact of virtual spilled oil reaching shoreline based on oil spill model simulations, or simply considering the vessel shoreline proximity as impact factor. The integration of an oil spill model in the shoreline risk levels, combined with adequate metocean modeling forecasts, allow a more realistic approach in the assessment of shoreline impacts, which can become even more important in case of regions with greater variability in marine weather conditions. The risk assessment from historic data can help finding typical risk patterns, “hot spots” or developing sensitivity analysis to specific conditions, whereas real time risk levels can be used in the prioritization of individual ships, geographical areas, strategic tug positioning and implementation of dynamic risk-based vessel traffic monitoring.