UAS-SfM Monitoring of Gully Erosion at the Main Ridge Site, Pueblo Grande de Nevada (Lost City)

Abstract:

The Pueblo II period Main Ridge site is within Pueblo Grande de Nevada (Lost City), a loosely defined series of Virgin Branch Puebloan settlements in Moapa Valley. Originally recorded as a community of 44 houses by Harrington in the 1920s, Main Ridge now consists of only 20 intact or partially intact houses because of intensive gully erosion as Lake Mead has receded. We report on our ongoing work using unmanned aircraft systems (UAS) structure-from-motion (SfM) to characterize gully erosion and predict potential future erosion impacts during extreme precipitation events. Structure-from-motion was applied to UAS acquired imagery of Main Ridge site houses and intersecting gullies. Preliminary modeling has produced high resolution surface models that reveal extensive ongoing dissection of the Main Ridge Site area, anthropogenic features acting as catchments, and unstable sediments and channel networks susceptible to erosion during extreme precipitation events.