Mitigation, monitoring, and geomorphology related to gully erosion of archaeological sites in Grand Canyon (Arizona)

Gully erosion has been damaging archaeological sites in Grand Canyon during the last several decades. Erosion-control structures are more prone to damage flow when placed in reaches of very high local gradient. Intact structures are generally successful in slowing erosion or causing deposition of sediment.; Mean vertical accuracy of aerial photogrammetry ranged from 6–10 cm. Mean error reached a minimum of 5–6.5 cm when the ratio of point density to topographic ruggedness was ∼40. Vertical changes of less than ∼20 cm were mostly undected by the photogrammetry due to measurement error.; Repeat ground surveys showed that gullies erode most at knickpoints and in steep reaches, and that new knickpoints tend to form in relatively steep reaches of a given channel. An area-slope erosion threshold was identified and applied in a GIS-based model to show areas that are sensitive to gully erosion. Overall results indicate an upcatchment control of gully erosion.