Reconstructing landforms and surface processes from declassified intelligence satellite imagery

Historical declassified intelligence satellite imagery (e.g., CORONA and Hexagon) are used in archaeology to assess the distribution and preservation of archaeological site in many parts of the Old World, and especially in arid lands, where the poor plant cover does not hamper the opportunities offered by earth observation tools. The same approach can be applied to geomorphology to reconstruct the evolution of surface processes and landforms in areas where recent urbanization had obscured natural features. In this contribution, we illustrate a first application of this approach to reconstruct the riverscape of the Tigris River in northern Iraq. The Mosul Dam reservoir in the Kurdistan Region of Iraq was built along the Tigris River between 1981 and 1988, submerging the course of the Tigris River for ca 100 km. Geomorphological mapping based of historical images derived from declassified Corona satellite imagery acquired between December 1967 and August 1968 reveals the pristine pattern of the Tigris River. Different spy images are snapshots of the seasonal changes of the Tigris riverbed, shifting from meandering to anabranching across the hydrological year, and illustrate the dynamic fluvial landforms such as the floodplain and point, middle, and longitudinal bars. Our approach underlines the relevance of historical declassified intelligence satellite imagery to reconstruct the ancient fluvial landscape below the Mosul Dam Lake and correlate it with litho-structural factors. We demonstrate the importance of historical aerial/satellite imagery in interpreting past natural geomorphic processes and landforms that suffered altering by human agency.