Debris flows as agents of morphological heterogeneity at low-order confluences, Olympic Mountains, Washington

Abstract

Research Article| September 01, 2003 Debris flows as agents of morphological heterogeneity at low-order confluences, Olympic Mountains, Washington Lee Benda; Lee Benda 1Earth Systems Institute, 310 North Mount Shasta Boulevard, Suite 6, Mount Shasta, California 96067, USA Search for other works by this author on: GSW Google Scholar Curt Veldhuisen; Curt Veldhuisen 2Skagit System Cooperative, 25944 Community Plaza Way, Sedro Woolley, Washington 98284, USA Search for other works by this author on: GSW Google Scholar Jenelle Black Jenelle Black 3Hart Crowser Incorporated, 1257 Main Street, Fortuna, California 95540, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Lee Benda 1Earth Systems Institute, 310 North Mount Shasta Boulevard, Suite 6, Mount Shasta, California 96067, USA Curt Veldhuisen 2Skagit System Cooperative, 25944 Community Plaza Way, Sedro Woolley, Washington 98284, USA Jenelle Black 3Hart Crowser Incorporated, 1257 Main Street, Fortuna, California 95540, USA Publisher: Geological Society of America Received: 26 Sep 2002 Revision Received: 10 Mar 2003 Accepted: 18 Mar 2003 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2003) 115 (9): 1110–1121. https://doi.org/10.1130/B25265.1 Article history Received: 26 Sep 2002 Revision Received: 10 Mar 2003 Accepted: 18 Mar 2003 First Online: 02 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 Lee Benda, Curt Veldhuisen, Jenelle Black; Debris flows as agents of morphological heterogeneity at low-order confluences, Olympic Mountains, Washington. GSA Bulletin 2003;; 115 (9): 1110–1121. doi: https://doi.org/10.1130/B25265.1 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 Effects of tributary junctions on longitudinal patterns of riverine heterogeneity are relevant to both fluvial geomorphology and riverine ecology. We surveyed 10 km of small- to moderate-sized mountain channels in the Olympic Peninsula, Washington, to investigate how low-order confluences prone to debris flow deposition directly and indirectly influenced channel and valley morphology. In the Olympic Mountains, debris flows scour sediment and organic material from steep first- and second-order channels and create deposits (debris fans) at tributary junctions in higher-order streams. In lower-energy depositional environments there were statistically significant relationships among debris fans at low-order confluences and gravel substrate, wide channels, and numbers of logs and large pools. Effects of debris fans on channel morphology extended upstream and downstream of fan perimeters, indicating the importance of indirect (offsite) effects of debris flows. Consequently, certain aspects of channel morphology (e.g., pool density, substrate texture, and channel widths) were nonuniformly distributed, reflecting the role of network topology and disturbance history on the spatial scale of morphological heterogeneity. Moreover, heterogeneity of channel morphology increased in proximity to low-order confluences prone to debris flows. In contrast, confluence effects in higher-energy depositional environments were limited. Our field data and information from seven other studies indicate how variation in debris flow volume and composition, stream energy, and valley width at the point of deposition influence the relationship between low-order confluences and channel morphology. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.