Field Report: UAV-Based Volcano Observation System for Debris Flow Evacuation Alarm

Once a volcano erupts, molten rocks, ash, pyroclastic flow, and debris flow can cause disasters. Debris flows can cause enormous damage over large areas. Therefore, a debris-flow simulation is an effective means of determining whether to issue an evacuation call for area residents. However, for safety purposes, restricted areas are set up around a volcano when it erupts. In these restricted areas, it is difficult to gather information such as the amount and permeability of the ash; this information is necessary for precise debris-flow simulations. To address this problem, we have developed an unmanned observation system for use in restricted areas around volcanoes. Our system is based on a multirotor micro unmanned aerial vehicle (MUAV); this system can be used to perform field tests in actual volcanic areas. In this paper, we report the field tests conducted at Mt. Unzen-Fugen during November 2016. The field tests included a demonstration of an unmanned surface flow measurement device and the deployment and retrieval of a small ground vehicle and a drop-down-type ash-depth measurement scale using an MUAV. In addition, we discuss some of the lessons learned.