Insight into sediment transport processes on saline rangeland hillslopes using three-dimensional soil microtopography changes

Authors: NOUWAKPO, SAYJRO KOSSI - University Of Nevada; Weltz, Mark; MCGWIRE, KEN - Desert Research Institute; Williams, Christopher - Jason; AL-HAMDAN, OSAMA - Texas A&M University; GREEN, COLLEEN - Bureau Of Land Management

Submitted to: Earth Surface Processes and Landforms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2016
Publication Date: 9/27/2017
Citation: Nouwakpo, S., Weltz, M.A., McGwire, K., Williams, C.J., Al-Hamdan, O., Green, C.H.M. 2017. Insight into sediment transport processes on saline rangeland hillslopes using three-dimensional soil microtopography changes. Earth Surface Processes and Landforms. 42(4):681-696. https://doi.org/10.1002/esp.4013.
DOI: https://doi.org/10.1002/esp.4013

Interpretive Summary: In arid and semi-arid rangeland environments, an accurate understanding of runoff generation and sediment transport processes is key to developing effective management actions and addressing ecosystem response to changes. Yet, many primary processes (namely sheet and splash and concentrated flow erosion, as well as deposition) are still poorly understood due to a historic lack of measurement techniques capable of parsing total soil loss into these primary processes. Current knowledge gaps can be addressed by combining traditional erosion and runoff measurement techniques with image-based 3D soil surface reconstructions. In this study, data (hydrology, erosion and high-resolution surface microtopography changes) from rainfall simulation experiments on twenty-four plots in saline rangelands communities of the Upper Colorado River Basin were used to improve understanding on various sediment transport processes. A series of surface change metrics were developed to quantify and characterize various erosion and transport processes (e.g., plot-wide vs. concentrated flow detachment and deposition) and were related to hydrology and biotic and abiotic land surface characteristics. In general, erosivity controlled detachment and transport processes while factors modulating surface roughness such as vegetation controlled deposition. The extent of the channel network was a positive function of slope, discharge and vegetation. Vegetation may deflect runoff in many flow paths and promoted deposition. This study suggests that effective runoff, soil erosion, and salt load reduction strategies can be met by increasing vegetation. Land management decisions should aim to promote deposition of transported sediments by increasing vegetation rather than reducing detachment which might not be feasible in these resource-limited environments.

Technical Abstract: In arid and semi-arid rangeland environments, an accurate understanding of runoff generation and sediment transport processes is key to developing effective management actions and addressing ecosystem response to changes. Yet, many primary processes (namely sheet and splash and concentrated flow erosion, as well as deposition) are still poorly understood due to a historic lack of measurement techniques capable of parsing total soil loss into these primary processes. Current knowledge gaps can be addressed by combining traditional erosion and runoff measurement techniques with image-based 3D soil surface reconstructions. In this study, data (hydrology, erosion and high-resolution surface microtopography changes) from rainfall simulation experiments on twenty-four plots in saline rangelands communities of the Upper Colorado River Basin were used to improve understanding on various sediment transport processes. A series of surface change metrics were developed to quantify and characterize various erosion and transport processes (e.g., plot-wide vs. concentrated flow detachment and deposition) and were related to hydrology and biotic and abiotic land surface characteristics. In general, erosivity controlled detachment and transport processes while factors modulating surface roughness such as vegetation controlled deposition. The extent of the channel network was a positive function of slope, discharge and vegetation. Vegetation may deflect runoff in many flow paths but promoted deposition. From a management perspective, this study suggests that effective runoff soil and salt load reduction strategies should aim to promote deposition of transported sediments rather than reducing detachment which might not be feasible in these resource-limited environments.