Robustness against different implementation of uncertainty in a contingency DSS: the Prestige oil spill revised

The dramatic consequences of oil or chemical spills for coastal ecosystems and economic uses make contingencymanagement a politically sensitive task. We here propose a new Decision Support System (DSS)consisting of a combination of modeling and evaluation methods with which different containment strategiescan be compared in the light of a variety of potential ecological and economic damages. In this study, the DSSis tested by hindcasting the Prestige accident off the coast of Spain in 2002. In particular, an oil spill contingencysimulation model coupled with multi-criteria analysis techniques was used to assess oil spill impacts forweather and current forecasts available at that time. Five different towing directions resulted in many differenthypothetical sinking sites which all were simulated separately. Two procedures of including the array of pollutionscenarios into the evaluation were considered: the first method uses expected pollution intensities for eachtowing route, in the second procedure all hypothetical sinking scenarios are rank–ordered so that towing directionsare only indirectly compared. Additional uncertainty resulting from incomplete or imprecise informationabout pollution impact thresholds or different weighting schemes representing major stakeholder groups is alsotaken into account. We identified clearly one worst option and one or two almost equally well performingroutes. For reasonable range limits of evaluation parameters or sinking probabilities, rankings turn out to berobust against the many uncertainties included so far. Even the two different methods of implementing varioussinking scenarios did only differ with respect to confidence limits. Robustness as well as transparency of thecoupled approach carry a large potential for enhancing the efficiency of decision making even in politicallysensitive situations.