r.avaflow v1, an advanced open source computational framework for the propagation and interaction of two-phase mass flows

Abstract

Abstract. r.avaflow represents an innovative open source computational tool for routing rapid mass flows, avalanches or process chains from a defined release area down an arbitrary topography to a deposition area. In contrast to most existing computational tools, r.avaflow (i) employs a two-phase, interacting solid and fluid mixture model; (ii) is suitable for modelling more or less complex process chains and interactions; (iii) explicitly considers both entrainment and stopping i.e. the change of the basal topography; (iv) allows for the definition of multiple release masses and/or hydrographs; and (v) serves with built-in functionalities for validation, parameter optimization and sensitivity analysis. r.avaflow is freely available as a raster module of the GRASS GIS software, employing the programming languages Python and C along with the statistical software R. We exemplify the functionalities of r.avaflow by means of two sets of computational experiments: (1) generic process chains consisting in bulk mass and hydrograph release into a reservoir with entrainment of the dam and impact downstream; (2) the prehistoric Acheron rock avalanche, New Zealand. The simulation results are generally plausible for (1) and, after the optimization of two key parameters, reasonably in line with the corresponding observations for (2). However, we identify some potential to enhance the analytic and numerical concepts. Further, thorough parameter studies are necessary in order to make r.avaflow fit for reliable forward simulations of possible future mass flow events.

Modeling the Glacial Lake Outburst Flood Process Chain in the Nepal Himalaya: Reassessing Imja Tsho's Hazard

“…Open-source software such as r.avaflow (Mergili et al, 2017) may contribute to future hazard analysis given the software's ability to model two-phase (i.e., solid debris and water) flow, once calibrated with real-world data. However, impulse wave dynamics are substantially affected by the chosen solid phase parameters in the underlying model (Pudasaini, 2014), 20 particularly the solids concentration within the lake, which requires more data and sensitivity analysis than a water-based model.…”

“…Shrestha et al (2013) included debris flow in a GLOF model of Tsho Rolpa, and assumed moraine failure from both seepage and overtopping; however, overtopping was due to a steady rise in the lake level and not due to an impulse wave. Recent studies have yielded more complex models regarding 20 multiphase debris flows such as the open-source r.avaflow, which can simulate an avalanche-induced GLOF process chain in a single model, but this model is still in development and has yet to be calibrated by observed real-world data (Mergili et al, 2017). A replicable process chain model for avalanche-induced GLOFs is therefore greatly needed to assess GLOF hazard throughout the Himalayas.…”

How well can we simulate complex hydro‐geomorphic process chains? The 2012 multi‐lake outburst flood in the Santa Cruz Valley (Cordillera Blanca, Perú)

“…r.avaflow is described in full detail by Mergili et al . (). Essentially, only those aspects relevant for the back‐calculation of the 2012 Santa Cruz process chain are outlined in this section.…”

“…Only those elements relevant for the present study are shown. See Mergili et al () for a comprehensive logical framework. [Colour figure can be viewed at wileyonlinelibrary.com]…”

“…This model has been applied to simulate generic examples representing submarine landslides and particle transport in lakes (Kafle et al ., ), and GLOFs (Kattel et al ., ). The computational tool r.avaflow (Mergili et al ., ) employs an enhanced version of the Pudasaini () model. Appropriate, well‐documented and well‐understood case studies are needed to test the suitability of this novel model and its computational implementation for real‐world events.…”