Lahar Inundation Estimation of Mount Semeru Relating to the 4th December 2021 Volcano Eruption

The Semeru volcano – located at the boundary region of Lumajang and Malang districts of East Java province, Indonesia – which is categorized as one of the active volcanoes in Indonesia was enormously erupted the volcanic materials – the hot lahar and the volcanic ash - on 4th December 2021. The scale of the eruption event caused some disaster to several villages along the path of the lahar and volcanic ash in south to southeast direction from the Mount Semeru lahar dome. An inundation simulation of the lahar is done as a contribution to mitigating the disaster that may potentially occur in the future. The LAHARZ algorithm was used for these estimation calculations. The Digital Terrain Model (DTM) and Digital Surface Model (DSM) were used as the base data for estimating and simulating the lahar inundation scenario. The use of two types of elevation model data in the simulation was done for study the inundation characteristics in the presence of forest vegetation. Three scenarios of lahar volume were used for simulating the inundation over elevation models. Results of the estimation then be compared to the actual lahar inundation that was delineated from the high-resolution satellite images. Lahar flow simulations using DTM show that more flows were formed compared to using DSM. The DTM simulation results showed a flow that more closely resembled the existing flow map compared to the DSM simulation results.