Modelling Individual Evacuation Decisions during Natural Disasters: A Case Study of Volcanic Crisis in Merapi, Indonesia

Abstract

As the size of human populations increases, so does the severity of the impacts of natural disasters. This is partly because more people are now occupying areas which are susceptible to hazardous natural events, hence, evacuation is needed when such events occur. Evacuation can be the most important action to minimise the impact of any disaster, but in many cases there are always people who are reluctant to leave. This paper describes an agent-based model (ABM) of evacuation decisions, focusing on the emergence of reluctant people in times of crisis and using Merapi, Indonesia as a case study. The individual evacuation decision model is influenced by several factors formulated from a literature review and survey. We categorised the factors influencing evacuation decisions into two opposing forces, namely, the driving factors to leave (evacuate) versus those to stay, to formulate the model. The evacuation decision (to stay/leave) of an agent is based on an evaluation of the strength of these driving factors using threshold-based rules. This ABM was utilised with a synthetic population from census microdata, in which everyone is characterised by the decision rule. Three scenarios with varying parameters are examined to calibrate the model. Validations were conducted using a retrodictive approach by performing spatial and temporal comparisons between the outputs of simulation and the real data. We present the results of the simulations and discuss the outcomes to conclude with the most plausible scenario. of 30year, Indonesia was the fourth most frequently affected Asian country [4]. Among the various natural hazards, volcanic eruptions pose a significant threat to Indonesia, as it is located within the "Ring of Fire" [5]. Merapi is the most active volcano in Indonesia, and the 2010 eruption was ranked third in the world since 2005 in terms of impact [4]. Being in such susceptible areas, people living close to Merapi should, therefore, develop their awareness and preparedness to evacuate when a hazard occurs.Evacuation is an important life-saving action in any disaster [6], with a history as old as human history in saving lives from natural disasters [7]. It takes place by moving people from a hazardous area to a safer place in a very limited time [8]. This time limit depends on the speed of the onset of the hazard. Some hazards occur rapidly, with others more slowly [1,9]. For example, hurricanes or earthquakes happen very quickly, while global temperature variations, rises in sea level, drought, and disease affect society more slowly [9]. For fast-onset hazards, immediate responses leading to evacuation are needed, because being at the wrong place at the wrong time will quickly lead to fatalities. Volcanic eruptions can happen several days after the initial signs of instability, but it is also possible for them to happen several weeks later [10]. Therefore, immediate responses from the surrounding population are needed, but there are often cases of people who refuse, or are reluctant to evacuate from hazardous are...

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“…Social simulations and computational models not only allow for discovery of the consequences of theories in artificial societies, but by enforcing formalization in terms of coherent programs, they play a similar role in social sciences as mathematics does in physical sciences [127]. Examples of this technique applied to disasters include [128][129][130][131]. Simulation is an alternative to common static modeling approaches in social sciences.…”

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