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ARS Home » Pacific West Area » Tucson, Arizona » SWRC » Research » Research Project #433339

Research Project: Channel and Landscape Evolution as a Function of Spatial Scale in Semiarid Watersheds

Location: Southwest Watershed Research Center

Project Number: 2022-13610-012-25-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 17, 2017
End Date: Sep 16, 2019

Objective:
The objective of this research is to evaluate and quantify geomorphic adjustment of ephemeral channels and relate channel evolution to runoff and sediment fluxes. Changing climate and predictions of increasing rainfall intensities may alter surface runoff, erosion, and channel morphologies. Although our process based understanding of erosion dynamics is incorporated in simulations models, the pulsing nature of water and sediment within and through semiarid watersheds, and the impacts on landscape evolution, are less well understood and quantified. One specific study site will be the USDA-ARS Walnut Gulch Experimental Watershed main channel and its tributaries. In 1935 Walnut Gulch was a wide, sand bed channel with extensive braiding in the lower reaches and little in-channel vegetation. These physical characteristics are consistent with conveyance of large magnitude flows that minimized vegetation had established on sediment deposits. Better information on landscape response to the temporal dynamics of runoff and sediment fluxes is needed from both theoretical and experimentally based perspectives. Results will contribute to ongoing research, and will contribute to research based on long-term observations from ARS and Long Term Agro-ecosystems Research (LTAR) locations. Although semiarid areas are known to be sensitive to climate, the LTAR network provides a framework for developing new knowledge across climate regimes to determine the impacts of evolving agricultural practices on watershed and landscape morphology thus ensuring landscape sustainability.

Approach:
Aerial photography, field surveys; aerial and ground based lidar, and simulation modeling will be used to quantify planform and channel cross section geometry and to quantify sediment transport. Runoff measurements collected at supercritical flumes located along the channel will be coupled with geomorphic measurements to interpret the evolution of the channel and relate to regional patterns of channel aggradation.