Headwater channel dynamics in semiarid rangelands, Colorado high plains, USA

Research Article| July 01, 2006 Headwater channel dynamics in semiarid rangelands, Colorado high plains, USA Gregory E. Tucker; Gregory E. Tucker 1Cooperative Institute for Research in Environmental Sciences (CIRES) and Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309, USA Search for other works by this author on: GSW Google Scholar Lee Arnold; Lee Arnold 2School of Geography and the Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, UK Search for other works by this author on: GSW Google Scholar Rafael L. Bras; Rafael L. Bras 3Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Search for other works by this author on: GSW Google Scholar Homero Flores; Homero Flores 3Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Search for other works by this author on: GSW Google Scholar Erkan Istanbulluoglu; Erkan Istanbulluoglu 4Department of Geosciences, University of Nebraska, Lincoln, Nebraska 68588, USA Search for other works by this author on: GSW Google Scholar Peter Sólyom Peter Sólyom 5School of Geography and the Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, UK Search for other works by this author on: GSW Google Scholar Author and Article Information Gregory E. Tucker 1Cooperative Institute for Research in Environmental Sciences (CIRES) and Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309, USA Lee Arnold 2School of Geography and the Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, UK Rafael L. Bras 3Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Homero Flores 3Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Erkan Istanbulluoglu 4Department of Geosciences, University of Nebraska, Lincoln, Nebraska 68588, USA Peter Sólyom 5School of Geography and the Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, UK Publisher: Geological Society of America Received: 03 Nov 2005 Revision Received: 03 Feb 2006 Accepted: 20 Feb 2006 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2006) 118 (7-8): 959–974. https://doi.org/10.1130/B25928.1 Article history Received: 03 Nov 2005 Revision Received: 03 Feb 2006 Accepted: 20 Feb 2006 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Gregory E. Tucker, Lee Arnold, Rafael L. Bras, Homero Flores, Erkan Istanbulluoglu, Peter Sólyom; Headwater channel dynamics in semiarid rangelands, Colorado high plains, USA. GSA Bulletin 2006;; 118 (7-8): 959–974. doi: https://doi.org/10.1130/B25928.1 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 Incised ephemeral channels provide a window into the fluvial processes that help sculpt rangeland landscapes. This paper presents observations of ephemeral channels and valley networks in the high plains of Colorado, USA, with an eye toward painting a picture of the ingredients that must be included in mathematical models of landscape evolution in such environments. Channel incision in the study area is driven by summer thunderstorms, which can with reasonable frequency (3–5 yr) generate boundary shear stresses high enough to penetrate the highly resistant vegetation armor, but only within erosional hot spots where hydraulic forces are amplified by channel constriction and locally steep gradients. Focusing of erosion at these hot spots (which correspond to knickpoints and channel heads) is amplified by the small areal footprint and short "erosional reach" of most convective storms. Upstream migration of knickpoints creates a pattern of short, active channel reaches separated by unchanneled or weakly channeled, fully vegetated stable reaches. Based on our observations, we interpret the necessary and sufficient conditions leading to the observed channel forms and dynamics as: (1) a resistant vegetation layer overlying an erodible substrate, which sets up a conditional instability through which erosional perturbations can grow by positive feedback; (2) high flow variability; (3) moderate to high substrate cohesion; and (4) a high volume fraction of fine-grained erodible material. Concave-upward valley long profiles are interpreted as a trade-off between downstream-increasing flood frequency and downstream-decreasing flood effectiveness. The observed process dynamics imply that long-term rates of valley incision should be especially sensitive to climatic oscillations between episodes of drought and warm-season convective rainfall. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.