Forecasting inundation from debris flows that grow during travel, with application to the Oregon Coast Range, USA

Geomorphology
By: , and 

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Abstract

Many debris flows increase in volume as they travel downstream, enhancing their mobility and hazard. Volumetric growth can result from diverse physical processes, such as channel sediment entrainment, stream bank collapse, adjacent landsliding, hillslope erosion and rilling, and coalescence of multiple debris flows; incorporating these varied phenomena into physics-based debris-flow models is challenging. As an alternative, we embedded effects of debris-flow growth into an empirical/statistical approach to forecast potential inundation areas within digital landscapes in a GIS framework. Our approach used an empirical debris-growth function to account for the effects of growth phenomena. We applied this methodology to a debris-flow-prone area in the Oregon Coast Range, USA, where detailed mapping revealed areas of erosion and deposition along paths of debris flows that occurred during a large storm in 1996. Erosion was predominant in stream channels with slopes > 5°. Using pre- and post-event aerial photography, we derived upslope contributing area and channel-length growth factors. Our method reproduced the observed inundation patterns produced by individual debris flows; it also generated reproducible, objective potential inundation maps for entire drainage networks. These maps better matched observations than those using previous methods that focus on proximal or distal regions of a drainage network.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Forecasting inundation from debris flows that grow during travel, with application to the Oregon Coast Range, USA
Series title Geomorphology
DOI 10.1016/j.geomorph.2016.07.039
Volume 273
Year Published 2016
Language English
Publisher Elsevier
Contributing office(s) Volcano Science Center
Description 16 p.
First page 396
Last page 411