Modelling lahars at Merapi (Indonesia) and Rainier (USA) volcanoes using Titan2D and LAHARZ computer models

Abstract

Lahars are a type of volcanic hazard that can have devastating impacts on surrounding environments and communities. They are difficult to predict and study, making them particularly dangerous. In order to better understand the extent and potential impacts of lahars, this study utilizes digital simulations and GIS technology to model lahar activity at Mount Merapi in Indonesia and Mount Rainier in the United States.The study employs the use of two computer codes, Titan2D and LAHARZ, to generate visual outputs for GIS systems. Titan2D is used to model near volcano hazards, such as pyroclastic density currents, using a Digital Elevation Model (DEM) of the volcano. These outputs are then remobilized as lahars and extended along valleys using LAHARZ, resulting in outputs that mimic real-life scenarios.Both Mount Merapi and Mount Rainier are located near densely populated settlements and have the potential to generate lahars, indicating a possibility for significant hazards. Using a 30-metre DEM and varying parameters, this study simulates lahars of varying volumes ranging from 125,000 m3 to 16,000,000 m3 in order to identify the extent of the hazard in multiple scenarios.Both Titan2D and LAHARZ have been tested individually by researchers in the past and have been found to accurately recreate past events. This study tests their combined use as a tool for producing hazard maps viewable in GIS, which can aid in hazard prediction and analysis. The resulting hazard maps for both Mount Merapi and Mount Rainier are found to be comparable to existing hazard maps for these volcanoes, suggesting that the combination of Titan2D and LAHARZ is an effective tool for hazard analysis.