The Role of Geospatial Technology and Landform Mapping for Volcanic Secondary Hazard Anticipation in Semeru Volcano, Indonesia

The combination of geospatial technology and field-based evidence plays an important role and has become a fundamental information system for any disaster-related database, such as a map at the local and regional levels. This research aims to map the geomorphological conditions of the Semeru Volcano after the 2021 eruption and to identify the area of the rain-triggered lahar slide based on the geomorphological conditions. We used remote sensing, geographic information systems, and field surveys. Factors such as morphological condition, lava slide direction, granularity, and thickness were used to predict the secondary hazard zone. The results found that erosion and sedimentation processes of rain-triggered lahar materials dominated 32 landforms from the geomorphological analysis within the study area. The materials were massively distributed in the middle and low-depositional zones located in the Mandalika formation. The inverse distance weighted analysis of lahar materials showed that the distribution of lahar in the range of 0 - 18.5 m was piled up at the bottom of the deposition process. In addition, through granular analysis, fine materials were deposited at the lower zone as a continuous sedimentation process. The lahar direction analysis also shows that the lower zone is a dangerous slide zone with indications of many lava slides. This research proves that the combination of geospatial and field-based evidence can be used to predict the secondary volcano hazard.