Valid debris-flow models must avoid hot starts

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Abstract

Debris-flow experiments and models commonly use “hot-start” initial conditions in which downslope motion begins when a large force imbalance is abruptly imposed. By contrast, initiation of natural debris flows almost invariably results from small perturbations of static force balances that apply to debris masses poised in steep channels or on steep slopes. Models that neglect these static balances may violate physical law. Here we assess how the effects of hot starts are manifested in physical experiments, analytical dam-break models, and numerical models in which frictional resistance is too small to satisfy static force balances in debris-flow source areas. We then outline a numerical modeling framework that avoids use of hot starts. In this framework an initial static force balance is gradually perturbed by increasing pore-fluid pressure that may trigger the onset of debris motion. Subsequent increases in pore-fluid pressure, driven by debris motion, may then reduce the debris frictional strength, leading to high flow mobility.

Additional publication details

Publication type Conference Paper
Publication Subtype Conference Paper
Title Valid debris-flow models must avoid hot starts
DOI 10.25676/11124/173051
Year Published 2019
Language English
Publisher Association of Environmental and Engineering Geologists (AEG)
Contributing office(s) Volcano Science Center
Description 8 p.
Larger Work Type Book
Larger Work Subtype Conference publication
Larger Work Title 7th International Conference on Debris-Flow Hazards Mitigation-Proceedings
First page 25
Last page 32
Conference Title Seventh International Conference on Debris-Flow Hazards Mitigation
Conference Location Golden, CO
Conference Date June 10-13, 2019
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