Mathematical models of erosive flash floods, huaycos and lahars

Huaycos - flash floods in the Peruvian Andes - and lahars – volcanic debris flows - are potent natural hazards that threaten regularly lives and livelihoods. They comprise debris-laden fluid that flows rapidly down steep slopes, bulking up considerably through erosion of the underlying bed as they progress. Owing to their rapid onset and the significant threat that they pose to communities and infrastructures, it is important to predict their motion to assess quantitatively some of the impacts that they may cause. This paper presents a new mathematical model of the physical processes that govern the motion and a new, free-to-use implementation of a numerical algorithm to integrate them, which may be used to predict the flows quantitatively.