To go or not to go when the lava flow is coming? Understanding evacuation decisions of Goma inhabitants during the 2021 Nyiragongo eruption crisis

During a volcanic eruption, evacuation of exposed population is one of the most effective mitigation actions. However, if the eruption is not preceded by precursors nor guidelines by authorities, such as the 2021 Nyiragongo eruption, inhabitants living near the volcano need to rapidly decide by themselves whether to evacuate or not; and if so, where, when and how. On the evening of 22 May 2021, a red glow on the south flank of Nyiragongo alerted the population of Goma (East DRC) that an eruption had started. There were no instructions from the authorities, but on that night, part of the population self-evacuated and returned the following day as the lava had stopped flowing. In the following week, intense seismic shocks affecting the city led the North Kivu military governor to order, on May 26, an evacuation of the eastern neighbourhoods of the city. Using qualitative interviews associated with a quantitative survey of 1137 adults living in both mandatory and non-mandatory evacuation zones, this study analyses individual evacuation decision during both volcanic and seismic phases of the 2021 Nyiragongo eruption. The results indicate that the population in the north-eastern neighbourhoods self-evacuated on the night of the eruption without prior knowledge of their destination; women being more likely to evacuate than men. The decision to evacuate was not influenced by an individual risk assessment, but by the family safety. Following the May 26 evacuation order, 56% of participant households evacuated but were wishing to rapidly return to protect their home. Living in the east neighbourhoods was a major factor of evacuating during the two evacuations. Those who did not evacuate considered the risk to be lower and manageable, in comparison to the 2002 disaster. Heuristic bias plays a strong role in inhibiting the evacuation intention. This unique analysis of evacuation behaviour during a complex volcanic crisis provides insights about elements influencing the evacuation decision, which might be of relevance for other volcanic crisis worldwide.