RESEARCH ARTICLE Historical aerial and terrestrial photographs for the investigation of mass movement dynamics in the Ethiopian Highlands Jan Kropáček 1 | Zuzana Vařilová 2 | Jan Nyssen 3 1 Department of Applied Geoinformatics and Spatial Planning, Czech University of Life Sciences Prague, Prague 165 00, Czech Republic 2 Department of Geology, Municipal Museum of Ústí nad Labem, Ústí nad Labem 40001, Czech Republic 3 Department of Geography, Ghent University, Ghent 9000, Belgium Correspondence Jan Kropáček, Department of Applied Geoinformatics and Spatial Planning, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, Prague 165 00, Czech Republic. Email: jkropacek@fzp.czu.cz Funding information Deutsche Forschungsgemeinschaft, Grant/ Award Number: HO1840/11‐1; Grantová Agentura České Republiky, Grant/Award Number: P209/12/J068 Abstract The edges of the Ethiopian Plateau are affected by frequent landslides predisposed by pronounced seasonality in precipitation, thick weathering mantle of volcanic material, and rough relief. We analyzed the three‐dimensional dynamics of three large land- slides in Dessie using digital elevation models and ortho‐images derived from a time‐ series of aerial photographs reaching back to 1936. Furthermore, we utilized repeated photography based on terrestrial photographs from the 1930s and 1940s to analyze landscape changes. It was revealed that the large sliding zone (25.4 ha) in lacustrine sediments at Kerra locality existed approximately in the present extent already before 1936. The volume of depleted material of the 1986–1994 rock slide at Doro Mezleya locality was assessed as 1.82 10 6 m 3 with mean vertical thickness of 48 m. Addition- ally, we described the nowadays inactive Hot Spring landslide (12.9 ha). We docu- mented a large scale reforestation of the area carried out as a remediation measure and rapid changes in land cover and settlement structure. We conclude that two out of three studied large landslides existed before 1936 and thus are not induced by the increased human pressure on the landscape of the last decades. Additionally, we provide an overview about collections of historical aerial photographs of Ethiopia, and we discuss their potential and drawbacks for mass wasting studies. KEYWORDS Dessie, Ethiopian Highlands, historical aerial photographs, mass movements, repeated photography, volume change 1 | INTRODUCTION The value of aerial photographs (APs) for monitoring of landslide evolution has been long recognized (Rib & Liang, 1978; Van Westen & Getahun, 2003). Terrain features indicating landslides such as scarps, tension cracks, compression ridges, and front lobes can be identified by photointerpretation techniques (Chandler & Cooper, 1989; Walstra, Dixon, & Chandler, 2007). Photogrammetric approaches including generation of digital elevation models (DEMs), and ortho‐images from APs allow an accurate quantification of changes in extent and volume (Casson, Delacourt, Baratoux, & Allemand, 2003; Walstra et al., 2007). Since the last few years, the Structure‐from‐Motion (SfM) approach for terrain reconstruction originally developed by the com- puter vision community has been increasingly used for the generation of DEMs from terrestrial photographs and APs (Snavely, Seitz, & Szeliski, 2008; Westoby, Brasington, Glasser, Hambrey, & Reynolds, 2012). Because recently, SfM approach has been applied also on historical APs in landslide studies (Gomez, Hayakawa, & Obanawa, 2015; Kropáček, Schillaci, Salvini, & Märker, 2017). In the SfM approach, estimation of the camera parameters can be facilitated by a redundancy of the bundle adjustment solution. These are clear advantages of SfM in processing of archive APs often coming without calibration data over traditional photogrammetry solutions (Frankl Received: 13 September 2017 Revised: 29 October 2018 Accepted: 31 October 2018 DOI: 10.1002/ldr.3220 Land Degrad Dev. 2019;30:483–493. © 2018 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/ldr 483