Modeling oil spill risk and environmental vulnerability in Alaska Arctic waters
Alaska’s waters are rich in biological resources and are host to oil exploration/production activities and heavy vessel traffic, as well as bordered by land-based facilities that transfer, store, and handle oil. This combination of sensitive resources and potential oil spill sources increases the risk of a damaging spill. A screening-level analysis of the relative risk of oil spills to the marine waters of the state of Alaska was conducted. A detailed model of region- and season-specific environmental vulnerability for Alaska was developed, and was combined with spill incident rates and potential volumes of oil spills to construct the overall risk model and determine the regions and seasons of highest relative risk. The environmental vulnerability model was developed to determine the relative vulnerability of broad geographic regions to spilled oil and is based on the underlying vulnerability of habitats and representative species present in each region and season assessed. Habitat and species vulnerability scores were combined to produce a relative environmental vulnerability score for each region/season that was then multiplied by an oil type effects score to scale vulnerability by oil-specific toxicity, mechanical injury, and persistence. Oil spill incidents were analyzed for current spill and discharge probabilities and projected for future incident rates.
Environmental vulnerability, incident rate, and relative risk scores were typically higher in the summer months than during the winter due to migratory species presence and increased vessel traffic. The Beaufort Sea, Southeast Alaska, Aleutians, and Kodiak regions showed the highest relative risk for the current and future maximum most probable discharge scenarios. The Beaufort Sea, Southeast Alaska, Aleutians, Kodiak, and Cook Inlet regions showed the highest relative risk for the current and future worst case discharge scenarios. These results highlight the most vulnerable regions for which further study is recommended. This model can be applied to any geographic area of interest, and provides a simple, yet comprehensive and expandable methodology for determining baseline environmental vulnerability of large geographic regions. Inputs, assessment criteria, and assumptions are transparent and can be tailored to the region of interest and available data. Implementation of this model in conjunction with oil spill volume and incident rate data allows for an objective screening-level assessment of oil spill risk.