Disaster managers are in charge of encountering natural disasters, yet, more often supported by citizens, so-called spontaneous volunteers. Their help has repeatedly been reported to be valuable for reducing disaster scales, regarding an increase in natural disasters occurrences with devastating effects. However, their characteristic to emerge in large groups has led to an unpredictable influx at operating sites from the perspective of disaster management. Finally, this led to problems such as congestions and blocked emergency routes, overcrowded operating sites and hampering officials in doing their work. To address this unpredictability, we apply a design science research approach to design and develop an information system to predict the influx of spontaneous volunteers at operating sites. We examine three design requirements and ten design principles, that we instantiate in a prototype. We finally validate our design theory empirically with experts, who positively highlight its perceived usefulness, conciseness, extendibility, explanatory power
