| Morphologic changes of dated pre-Columbian agricultural terraces constructed by Wari and Inca cultures in southern Peru provide insight into the rate and pattern of dryland erosion over millennial time spans. An erosion rate of 0.1 mm yr-1 is calculated on these disturbed landscapes, more than thirty times faster than the 0.0034 mm yr-1 rate reported for natural landscapes determined from terrestrial cosmogenic nuclides, TCN analysis. Channels and spoon-shaped notches are the dominant erosional features developed on the c. 500 year old Inca and c. 1000 year old Wari terraces. The pre-terraced morphology of the hillside and the drainage contributing area determine the pattern of erosion. The hydrology of these disturbed hillslopes quickly reverts back to their initial, natural, conditions of the hillslope when they are no longer maintained.;The erosion rate and pattern determined from the historical approach used in this study are appropriate for short-term erosion of the anthropogenic structures constructed in dryland regions. Erosion rates derived from TCN, are more appropriate for long-term geologic time scales and for the morphologic evolution of natural landscapes. This study highlights the importance of context (spatial, temporal, and land use) in selecting reported erosion rates for different settings. |
