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USGS Navajo Land Use Planning Project (NLUPP)

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Landscape Surface Changes: We are attempting to document changes in local landscape conditions, the distribution of shrubs and juniper, and the history of arroyo incision. McFadden and McAuliffe (1997) suggest that changes in precipitation, rather than land use, have been largely responsible for arroyo formation, because of the highly erodible nature of regional bedrock, and its sensitivity to minor climatic change. The landscape of the Navajo Nation is characterized by ephemeral streams that have incised easily eroded fine-grained valley-fill, and highly erodible soft bedrock lithologies, such as the Bidahochi and Chinle Formations. This makes the region especially sensitive to short-term variations in precipitation and temperature. Preliminary work suggests that local erosion by alluvial processes is dominated by overland flow. Although processes that contribute to arroyo incision are complex, it is most likely attributed to changes in hillslope vegetation. Perturbations in plant cover affect discharge of water and sediment from hillslopes, hydraulic roughness, and the amount of surface sediment traps (Bull, 1997). Arroyo formation can result from precipitation changes or changes in grazing practices that we will decipher by examination of multi-date sets of aerial and historic photos to determine the temporal relation of surface change to land use and climatic fluctuations, and by monitoring sites selected by preliminary mapping. Monitoring and remote sensing can provide an important link between the geologic record and specific atmospheric processes that are required to understand the effects of climate change on geomorphic processes that govern landscape mobility and stability hydraulic roughness.

Examples of landscape change caused by surficial processes
Left: Arroyo east of Satan Butte, near Greasewood, AZ
Right: Eroding Parabolic Dune, south of Pyramid Butte, AZ
(images source: Margaret Hiza-Redsteer, USGS Flagstaff, AZ)
Bull, W. B., 1997. Discontinuous ephemeral streams: Geomorphology, v. 19 no. 3, p. 227-276.

McFadden, L. D., and McAuliffe, J. R., 1997, Lithologically influenced geomorphic responses to Holocene climatic changes in the southern Colorado Plateau: Geomorphology, v. 19, no. 3, p. 303-332.
 

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