<![CDATA[The 2010 eruption of Mt. Merapi was one of the largest eruptions in the last century. By generating pyroclastic density currents (PDCs) was devastating area more than 22 km2 across populated region, and the total casualties were estimated more than 390 peoples. Kendil ridge becomes a topographic barrier and blocks the pyroclastic material from the summit crater for overspill directly into other flank during the first stage on October 26th 2010 eruption. By understanding of catastrophic deadly event through numerical back-calculation is essential for the potential future impact. Extensive studies on PDCs simulations accurately reproducing flow behavior over complex topography remains challenging because the terrain-fitted coordinate system is based on the digital elevation model (DEM). However, numerical simulation often require topographic smoothing, which may alter surface deviation of flow patterns and material deposit. This research aims to improve the representation of complex terrains by incorporating sub-topography and an upwelling concept for represent gradual dome collapses in order to minimize random overbanking distribution and control a total volume collapse. To reconstruct travel distance of PDCs, the numerical simulation using Coulomb and Voellmy rheology formulations. The results describe that the Voellmy rheology effectively reduced excessive flow velocity from turbulent drag force on material flow and provided a more realistic representation of PDCs propagation. The simulation result were verified against previous research, and satellite imagery of the material flow distribution and found to be reasonably accurate. The average depth of material in a flank of Mt.Merapi up to 0.5-2 m until several meter deposits being common. The proposed approach provides valuable insight for volcanic hazard assessment and disaster risk reduction infuture eruptions.]]>
