This work presents a study of the biggest mudflow event in 20 years in Chilean Patagonia, which resulted from an avalanche in the Cordon Yelcho. We integrate in situ geotechnical tests and numerical modeling to model the Villa Santa Lucía mudflow event. Our results suggest that the initial soil water content is sufficient to transform the landslide and scoured soil into a mudflow. Therefore, knowing the soil characteristics is crucial to evaluating the impact of landslides in the study area.