Sediment storage and evacuation in headwater valleys at the transition between debris-flow and fluvial processes

Abstract

Research Article| November 01, 2007 Sediment storage and evacuation in headwater valleys at the transition between debris-flow and fluvial processes Stephen T. Lancaster; Stephen T. Lancaster 1Department of Geosciences, Oregon State University, Corvallis, Oregon 97331-5506, USA Search for other works by this author on: GSW Google Scholar Nathan E. Casebeer Nathan E. Casebeer 1Department of Geosciences, Oregon State University, Corvallis, Oregon 97331-5506, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Stephen T. Lancaster 1Department of Geosciences, Oregon State University, Corvallis, Oregon 97331-5506, USA Nathan E. Casebeer 1Department of Geosciences, Oregon State University, Corvallis, Oregon 97331-5506, USA Publisher: Geological Society of America Received: 27 Mar 2007 Revision Received: 22 Jun 2007 Accepted: 29 Jun 2007 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 The Geological Society of America, Inc. Geology (2007) 35 (11): 1027–1030. https://doi.org/10.1130/G239365A.1 Article history Received: 27 Mar 2007 Revision Received: 22 Jun 2007 Accepted: 29 Jun 2007 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Stephen T. Lancaster, Nathan E. Casebeer; Sediment storage and evacuation in headwater valleys at the transition between debris-flow and fluvial processes. Geology 2007;; 35 (11): 1027–1030. doi: https://doi.org/10.1130/G239365A.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 SocietyGeology Search Advanced Search Abstract Sediment from landscape disturbance often enters temporary storage in valleys and evacuates over longer times, which in steeplands are poorly delimited. We hypothesize that, across process transitions (e.g., debris flow versus fluvial transport), distributions of sediment transit times also change. We use field surveys and extensive radiocarbon dating to assess the distribution of transit (residence) times through the proxy measurement of ages of bank deposits in two mainstem reaches of a 2.23 km2 watershed in the Oregon Coast Range. In the downstream reach, debris fans impound fluvial deposits; debris-flow, fine fluvial, and coarse fluvial deposits compose nearly equal parts of the valley fill; and fluvial erosion evacuates deposits. Transit times have a sample mean of 1.22 × 10314C yr and an exponential distribution, indicating uniform probability of evacuation from storage. In the upstream reach, valley-spanning debris jams impound debris-flow deposits composing >95% of the valley fill, which is routinely scoured by debris flows. Transit times have a sample mean of 4.43 × 10214C yr and, if >100 14C yr, a power-law distribution, indicating preferential evacuation of younger deposits and retention of older deposits. In both reaches, most sediment has short transit times (<600 14C yr), but significant volumes remain for millennia. Less than 20% of basin-wide denudation passes through these reservoirs, but the latter are still significant buffers between hillslope disturbance and downstream aquatic habitat, especially for coarse sediment. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.