This paper introduces Titan2D, a depth averaged model of an incompressible Coulomb continuum for "shallow water" granular flows. Titan2D has been used successfully at many volcanoes to predict inundation by block-and-ash flows and debris avalanches. It can be run as a stand-alone program or through Vhub, a cyber-infrastructure platform. Practical considerations of choosing appropriate user inputs and the basics of running the model are discussed herein. Both synthetic and natural terrain examples are presented, including simulations of a block-and-ash flow generated from the gravitational collapse of a synthetic dome at Turrialba volcano (Costa Rica). These results suggest that the model should be limited to simulate cases of dense volcanic granular flows, like those produced by gravity-driven dome collapse events, but cannot be used to simulate dilute pyroclastic density currents. Finally, estimation of the Ti-tan2D resistance terms by using empirical relationships provides a good method for reducing model input uncertainties.

Numerical modeling; Titan2D; Turrialba volcano; shallow-water equations; volcanic hazards; hazard assessment; debris avalanche; block-and-ash flows