Home
A JFSP Fire Science Exchange Network
Bringing People Together & Sharing Knowledge in the Northern Rockies

A morphometric analysis of gullies scoured by post-fire progressively bulked debris flows in southwestern Montana, USA

Author(s): Emmanuel J. Gabet, Andy Bookter
Year Published: 2008
Description:

In the fall of 2001, an intense thunderstorm in southwest Montana triggered many debris flows in the burned area of Sleeping Child Creek. In most instances, the debris flows cut deep gullies into previously unchannelized colluvial hollows and deposited large volumes of sediment onto the valley floor. The presence of rill networks above the gullies as well as the absence of landslide features indicate that the gullies were scoured by progressively bulked debris flows, a process in which dilute surface runoff becomes increasingly more laden with sediment until it transforms into a debris flow. In this contribution, we present a morphometric analysis of six of the gullies to better understand this relatively understudied process. We find that the locations of the rill heads and gully heads conform to slope-area thresholds that are characteristic of erosion by overland flow. Our data also suggest that the volumes of the debris flows increase exponentially with normalized drainage area, thus lending support to an assumption used in a recently proposed debris flow incision law. Finally, the debris flow fans have been relatively unaltered since deposition, suggesting that the valley may be currently aggrading while the hillslopes are being denuded.

Citation: Gabet EJ, and Bookter A. 2008. A morphometric analysis of gullies scoured by post-fire progressively bulked debris flows in southwestern Montana, USA. Geomorphology 96(3-4): 298-309. https://doi.org/10.1016/j.geomorph.2007.03.016
Topic(s): Post-fire Management, Post-fire Rehabilitation, Erosion Control
Ecosystem(s): None
Document Type: Book or Chapter or Journal Article
NRFSN number: 18714
Record updated: Dec 11, 2018