Effects of sediment pulses on channel morphology in a gravel-bed river

Abstract

Research Article| January 01, 2007 Effects of sediment pulses on channel morphology in a gravel-bed river Daniel F. Hoffman; Daniel F. Hoffman 1Department of Geosciences, University of Montana, Missoula, Montana 59802, USA Search for other works by this author on: GSW Google Scholar Emmanuel J. Gabet Emmanuel J. Gabet 1Department of Geosciences, University of Montana, Missoula, Montana 59802, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2007) 119 (1-2): 116–125. https://doi.org/10.1130/B25982.1 Article history received: 06 Feb 2006 rev-recd: 06 Jun 2006 accepted: 03 Aug 2006 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Daniel F. Hoffman, Emmanuel J. Gabet; Effects of sediment pulses on channel morphology in a gravel-bed river. GSA Bulletin 2007;; 119 (1-2): 116–125. doi: https://doi.org/10.1130/B25982.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Sediment delivery to stream channels in mountainous basins is strongly episodic, with large pulses of sediment typically delivered by infrequent landslides and debris flows. Identifying the role of large but rare sediment delivery events in the evolution of channel morphology and fluvial sediment transport is crucial to an understanding of the development of mountain basins. In July 2001, intense rainfall triggered numerous debris flows in a severely burnt watershed in the Sapphire Mountains of Montana. Ten large debris flow fans were deposited on the valley floor, and investigations focused on the channel response to these sediment pulses. The channel has aggraded immediately upstream of each fan, and braided in reaches immediately downstream. Channel incision through the fans has created sets of coarse-grained terraces. The deposition upstream of the pulses consists almost exclusively of fine material, resulting in a median bed material size (D50) 1–2 orders of magnitude lower than the ambient channel material. The volume of sand being transported is so great that these aggrading reaches can extend hundreds of meters upstream of the fans, with 1–2 m of sand deposited across the entire valley floor. Along a 10 km study reach, cross section surveys, longitudinal profiles, and pebble counts chronicle channel response to a punctuated increase in sediment supply and provide insight on the processes of sediment wave dispersal. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.