Estimating flow concentration and sediment redistribution on saline rangeland communities

Authors: Weltz, Mark; NOUWAKPO, SAYJRO - UNIVERSITY OF NEVADA; MCGWIRE, KEN - DESERT RESEARCH INSTITUTE; ROSSI, COLLEEN - BUREAU OF LAND MANAGEMENT

Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/10/2015
Publication Date: 4/19/2015
Citation: Weltz, M.A., Nouwakpo, S.K., Mcgwire, K., Rossi, C. 2015. Estimating flow concentration and sediment redistribution on saline rangeland communities. Federal Interagency Sedimentation Conference Proceedings. p. 809-821.

Interpretive Summary: In arid and semi-arid rangelands where vegetation is typically sparse, a synergistic relationship is assumed to exist between spatial distribution of plants and hydrologic and erosion processes. In these environments, an accurate understanding of sediment transport processes is key to developing informed management actions and addressing ecosystem response to global changes. In this study, data from rainfall simulation experiments in saline rangelands communities of the Upper Colorado River Basin were used to improve understanding on various sediment and solute transport processes in field conditions. During these experiments, hydrology, erosion and high resolution surface soil roughness changes were routinely measured, presenting a unique opportunity to answer many sediment transport questions relevant to these saline rangelands and other sparsely vegetated ecosystems. A series of variables were developed to quantify and characterize surface soil roughness changes as a function of hydrology, soil erosion and hillslope configuration. Key findings from preliminary analyses include: (1) the dependence of deposition of soil on plot slope and its independence on hydrologic and soil loss variables, (2) data supporting the process of increased down-cutting as slope increased, (3) significance of accounting deposition processes in overall runoff energy quantification, (4) evidence of an equilibrium channel geometry with a given discharge that is marginally impacted by runoff duration.

Technical Abstract: In arid and semi-arid rangelands where vegetation is typically sparse, a synergistic relationship is assumed to exist between spatial distribution of plants and hydrologic and erosion processes. In these environments, an accurate understanding of sediment transport processes is key to developing informed management actions and addressing ecosystem response to global changes. In this study, data from rainfall simulation experiments in saline rangelands communities of the Upper Colorado River Basin were used to improve understanding on various sediment and solute transport processes in field conditions. During these experiments, hydrology, erosion and high resolution surface microtopography changes were routinely measured, presenting a unique opportunity to answer many sediment transport questions relevant to these saline rangelands and other sparsely vegetated ecosystems. A series of variables were developed to quantify and characterize surface microtopographic changes as a function of hydrology, erodibility and hillslope configuration. Key findings from preliminary analyses include: (1) the dependence of deposition on plot slope and its independence on hydrologic and soil loss variables, (2) data supporting the process of increased down-cutting as slope increased, (3) significance of accounting deposition processes in overall runoff energy quantification, (4) evidence of an equilibrium channel geometry with a given discharge that is marginally impacted by runoff duration.