Modeling lahars using Titan2D for the southern drainage of Volcan Cotopaxi: impact on the city of Latacunga

Lahars triggered by mobilization of deposits from volcanic explosions have occurred at Volcán Cotopaxi, Ecuador on the average of once every century over the last two millennia. Lahars from Cotopaxi may flow down three main drainages, impacting a present day population of around 3 million inhabitants. Río Cutuchi, the main drainage to the south of Cotopaxi, headwaters on the flanks of Rumiñahui and Cotopaxi Volcanoes. This river flows southwards through several communities, including the city of Latacunga (population 52,000). Its path is generally parallel to the Pan American highway. Many small scale lahars have followed this drainage, as well as some large scale historical flows, such as the great 1877 debris flow that severely impacted the population along the Río Cutuchi. This study used the Titan2D model to simulate lahars of various volumes that correspond to actual deposits along the Río Cutuchi in the vicinity of Latacunga. The purpose was to investigate the hazard that lahars might present to the current population should Cotopaxi become active again and produce debris flows. The study area is restricted to the region adjacent to Latacunga where detailed field data are compared with the model results. Simulations utilized topographic, stratigraphic, and historical inundation data collected in the field in the summer of 2005 to determine probabilistic lahar inundation zones for the debris flows of various sizes. These inundation zones have been analyzed in conjunction with infrastructure data for Latacunga so that the impact of various scale lahars on the city can be assessed.