Simulating glacial lake outburst floods with a two-phase mass flow model

Abstract

ABSTRACT. To simulate a glacial lake outburst flood, we employ a comprehensive physically based general two-phase mass flow model (Pudasaini, 2012). This model accounts for a strong interaction between the solid and fluid phases and incorporates buoyancy and other dominant physical aspects of the mass flows such as enhanced non-Newtonian viscous stress, virtual mass force and generalized drag. Our real two-phase mass flow simulation describes explicit evolution of the solid and fluid phases and the debris bulk as a whole, akin to torrential debris flows or debris floods during glacial lake outburst floods (GLOFs). The emptying of a lake following rapid collapse of a restraining dam, the consequent downslope motion of a mixed solid-fluid mass, and the tendency of the mass to form extruding plumes are analyzed in detail for different flow configurations, volumes, conduit geometries and boundary conditions. The solid and fluid phases evolve completely differently and reveal fundamentally different dynamical behaviours. During the flow, the relatively long fluid tail follows the solid-rich dense frontal surge head. The bulk debris develops into a frontal and side levee as derived from the initial frontal moraine dam. Results show that our high-resolution, unified simulation strategies and the advanced model equations can be applied to study the flow dynamics of a wide range of geophysical mass flows such as snow and rock-ice avalanches, debris flows and flash floods as well as GLOFs. This may help substantially in forming a basis for appropriate mitigation measures against potential natural hazards in high mountain slopes and valleys.

Back calculation of the 2017 Piz Cengalo–Bondo landslide cascade with r.avaflow: what we can do and what we can learn

“…tres away from the source and have led to major disasters in the past, such as the 1949 Khait rock avalanche-loess flow in Tajikistan (Evans et al, 2009b), the 1962 and 1970 Huascarán rockfall-debris avalanche events in Peru (Evans et al, 2009a;Mergili et al, 2018b), the 2002 Kolka-Karmadon ice-rock avalanche in Russia (Huggel et al, 2005), the 2012 Seti River debris flood in Nepal (Bhandari et al, 2012), or the 2017 Piz Cengalo-Bondo rock avalanche-debris flow event in Switzerland. The initial fall or slide sequences of such process chains are commonly related to a changing cryosphere characterized by glacial debuttressing, the formation of hanging glaciers, or a changing permafrost regime (Harris et al, 2009;Krautblatter et al, 2013;Haeberli and Whiteman, 2014;Haeberli et al, 2017).…”

DebrisInterMixing-2.3: a finite volume solver for three-dimensional debris-flow simulations with two calibration parameters – Part 2: Model validation with experiments

“…The mixture of different materials leads to a complex rheological behavior that is still not well understood. Field observations of debris-flow behavior and rheology are challenging and still rare, and numerical modeling is often the approach of choice when assessment of debris-flow behavior is needed for planning, zoning and hazard assessment (Scheuner et al, 2011;Christen et al, 2012;Kattel et al, 2016;Mergili et al, 2017). Most models require direct calibration to capture the site-specific behavior.…”

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

“…Pudasaini () proposed such a general two‐phase flow model. 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.…”