Journal of the ASABE Vol. 66(1): 155-166 © 2023 American Society of Agricultural and Biological Engineers ISSN 2769-3295 https://doi.org/10.13031/ja.15254 155 USING GOOGLE EARTH IMAGERY TO T ARGET ASSESSMENTS OF EPHEMERAL GULLY EROSION David A. Reece 1 , John A. Lory 2,* , Timothy L. Haithcoat 3 , Brian K. Gelder 4 , Richard Cruse 5 Collection Research 1 Division of Plant Sciences and Technology, University of Missouri, Columbia, Missouri, USA. 2 Division of Plant Sciences, University of Missouri, Columbia, Missouri, USA. 3 Institute for Data Science and Informatics, University of Missouri, Columbia, Missouri, USA. 4 Agricultural Engineering, Iowa State University, Ames, Iowa, USA. 5 Agronomy, Iowa State University, USA. * Correspondence: loryj@missouri.edu HIGHLIGHTS  Tested the utility of Google Earth and other imagery to target the location of ephemeral gullies.  Developed a targeting methodology and tested it based on a ground truth obtained using a UAV.  Quantified the overlap of targeted areas with observed ephemeral gullies.  These publicly available sources of imagery had a high degree of success in identifying where ephemeral gullies form. ABSTRACT. Sustaining civilizations requires preventing the loss of agricultural topsoil through processes such as water and wind erosion. Ephemeral gully erosion contributes an estimated 40% of the total water-erosion soil loss from row-crop fields. The identification and tracking of gullies require monitoring fields over time; Google Earth provides high-quality imagery that can potentially meet both the temporal and spatial criteria for ephemeral gully monitoring. Our primary ob- jective was to determine the probability that an ephemeral gully erosion feature could be reliably identified as an area of concern based on Google Earth imagery and/or other publicly available remotely sensed imagery. To develop the ground truth, we visited 72 fields in seven Missouri counties between mid-April and mid-June in 2018 (n = 26), 2019 (n = 21), and 2020 (n = 25) to verify the presence of erosion features. An unmanned aerial vehicle (UAV) was used to collect aerial imagery with an estimated ground sampling distance of 2.1 to 2.7 cm pixel -1 from all locations. From this imagery, ephem- eral gullies were observed in 24 of the fields, and all ephemeral gullies in those fields were delineated. We then reviewed all imagery available in Google Earth from 2010 to 2020 for the 24 fields where ephemeral gullies were observed, deline- ating ephemeral gully features using a “definitive” and a “less stringent” criterion; we also evaluated 2008 and 2015 imagery from a second public source. In the first analysis, one random erosion feature was chosen from each field, and the percentage overlap of lines derived from publicly available information with the ground truth was determined. Combining all imagery sources, using the less stringent method of delineation, and applying a 15-m buffer resulted in a mean overlap rate of 91%. These results were superior to the definitive approach, as well as using a 3-m buffer. In a second analysis, we tested definitive and less stringent criteria in the field for simple intersection with the ground truth. The less stringent strat- egy, coupled with using a 15-m buffer, had a true positive rate of 81% and identified 100% of the ephemeral gullies at 63% of the locations. There were false positives in 38% of the fields, with a mean rate across locations of 15%. Adding public data from other sources improved the true positive rate while also increasing the false negative rate. At one location, all publicly available image sources failed to identify the single ephemeral gully in the field. This research represents a proof of concept that Google Earth and other publicly available imagery of sufficient quality can be used to target in-field ephem- eral gully assessment in row crop fields in the humid regions of the US. Validation work is needed before this approach can be broadly adopted with confidence, given the many uncontrollable factors that can affect the efficacy of this approach. Keywords. Aerial imagery, Conservation compliance, Ephemeral gully, Remote sensing, Soil erosion. oil erosion rates exceed rates of soil formation in many row-cropped fields in the US and globally (Montgomery, 2007; Cruse et al., 2013; Pennock, 2019). Sustaining agriculture and the societies it supports requires protecting topsoil from both wind and wa- ter erosion (Montgomery, 2012; Pennock, 2019; Weltz et al., 2020). Water erosion processes are typically divided into four categories: sheet, rill, ephemeral gully, and classic gully Submitted for review on 30 June 2022 as manuscript number NRES 15254; approved for publication as a Research Article and as part of the Soil Erosion Research Symposium Collection by Associate Editor Dr. Prasad Daggupati and Community Editor Dr. Kyle Mankin of the Natural Resources & Environmental Systems Community of ASABE on 15 December 2022. S