TITAN2F code for lahar hazard assessment: derivation, validation and verification

Abstract

Debris flows, lahars, avalanches, landslides, and other geophysical mass flows can contain material in the order of O(10 6-10 10) m 3 or more. These flows commonly consist of a mixture of soil and rocks with a significant quantity of interstitial fluid. They can be tens of meters deep, and their runouts can extend many kilometers. The complicated rheology of such a mixture challenges every constitutive model that can reasonably be applied: The range of length and timescales involved in such mass flows challenge the computational capabilities of existing models. This paper extends recent efforts to develop a depth averaged "thin layer" model for geophysical mass flows that contain a mixture of solid material and fluid. Concepts from the engineering community are integrated with phenomenological findings in geoscience, resulting in a theory that accounts for the principal solid and fluid forces as well as interactions between the phases, across a wide range of solid volume fractions. A principal contribution here is to present drag and phase interaction terms that conform with the literature in geosciences. The Titan2F program predicts the evolution of the volumetric concentration of solids and dynamic pressure. The theory is validated with data from one-dimensional dam break solutions and with data from artificial channel experiments.

Lahars and debris flows: Characteristics and impacts

“…Forecasting debris-flow speeds and inundation areas commonly entails the use of physically based, deterministic flow dynamic simulations (Iverson, 2014). Models that describe flow mechanics can incorporate probabilistic components by adopting a range of plausible values for material properties and initial conditions, computing a corresponding range of possible outcomes (Córdoba et al, 2015(Córdoba et al, , 2018. Probabilistic DF inundation forecasts can be accomplished by exploiting statistical patterns exhibited by prior events.…”

Modeling Tephra Fall and Sediment-Water Flows to Assess Their Impacts on a Vulnerable Building Stock in the City of Arequipa, Peru

“…Computational models or numerical codes have become one of the most important tools for HCF/DF hazard assessment. Thouret et al (2020), their Table 4 elaborated on a list of models used for simulating lahars or HCFs/DFs, such as LAHARZ-py (Schilling, 2014), Titan2D (Pitman and Le, 2005;Williams et al, 2008) and Titan2F (Córdoba et al, 2015;Córdoba et al, 2018), FLO-2D (O'Brien et al, 1993), RAMMS (Cesca and D'Agostino, 2008), and VolcFlow (Kelfoun and Druitt, 2005). We tested three models, Titan2F, VolcFlow, and FLO-2D, all shallowwater depth-averaged models for modeling HCFs and DFs in the Qdas.…”

A Modeling Approach for Lahar Hazard Assessment: the Case of Tamasagra Sector in the City of Pasto, Colombia

“…Titan2F was developed to account for both of the phases keeping a reasonable computational cost [8], [21]. The fluid part of the flow is modeled using typical shallow water like approach, whereas the frictional behavior of the solid phase is accounted by assuming that Mohr-Coulomb law is valid in such case, as in [17] and [18].…”

“…The equation system is further integrated by depth averaging [17] (see [21], [8] for details), which is computationally cheap because is a 2D approach over a three dimensional topography. This approach is known as a pseudo-3D approach.…”