Palisade’s (www.palisade.com) leading risk analysis tool, The DecisionTools Suite, is being used by the University of Bristol’s Environmental Risk Research Centre (BRISK) to add a new dimension to modelling volcanic risk in Guatemala. The ‘Volcán de Fuego’ is potentially one of the most dangerous volcanoes in Central America with a large population surrounding it, and many farmers live and work in its shadow due to the fertile slopes that provide the best ground for coffee growing in the region. Recent work there using The DecisionTools Suite proved invaluable in mitigating the risks associated with any eruption.

As an integrated set of programs for risk analysis and decision making under uncertainty, The DecisionTools Suite runs in Microsoft Excel and allows BRISK to run Monte Carlo simulation and other advanced analytics quickly and simply on a laptop in the field. Conventional risk assessments have attempted to model the probability of a hazard and combined that with the vulnerability of the population, to create societal risk curves or values of Individual Risk per Annum (IRPA). However, using The DecisionTools Suite’s Monte Carlo sampling, the BRISK group have gone a step further and developed a unique way of modelling the likelihood of a successful evacuation. This has been carried out using @RISK and PrecisionTree, both part of the suite, by inputting several variables obtained through a process of structured expert judgment.

Jonathan Stone, a researcher at the University of Bristol, working with colleagues Prof Willy Aspinall (see Note 1) and Dr Matt Watson, said: “Conducting a quantitative risk assessment is a difficult process, often requiring data that is sparse or even unobtainable. With volcanoes, the effects of the uncertainty are accentuated by the potentially high costs of making a wrong call. The volcano has been very active over the last few years, and the fear is that this activity could suggest the build up towards larger eruptions.”

He continued, “The Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia (INSIVUMEH) monitors activity at the volcano. However, despite the gallant efforts of the scientists there, no formalised risk assessments were carried out, mainly due to lack of funding. Using @RISK and The DecisionTools Suite has enabled volcanologists to quantify the nature of the threat from the volcano to people’s lives.”

The new approach has modelled the likelihood that the people in the region will need to be evacuated if the volcano’s activity increases. It uses @RISK and PrecisionTree to input several variables, including the time between an eruption starting and a hazard hitting a location, along with the warning time that may come from the authorities and the time the population needs for evacuation. All of these are difficult to predict with any accuracy and need to be represented by appropriate uncertainty distributions by the experts. By a special elicitation process, these expert views are weighted and then pooled together. The variables and their uncertainties are combined in a logic tree within PrecisionTree, with the end result being the probability of successful evacuation, or not. When fed back in the @RISK model, the beneficial effects of evacuation on risk, and the costs of failure, are made very clear.

Stone concluded, “Palisade’s DecisionTools Suite has proved to be invaluable in the work we are doing with INSIVUMEH, and potentially very useful for those living and working around Volcán de Fuego.”