Declassified intelligence satellite imagery as a tool to reconstruct past landforms and surface processes. The submerged riverscape of the Tigris River below the Mosul Dam Lake, Iraq

Located along the Tigris River in the Kurdistan Region of Iraq, the Mosul Dam reservoir is the second biggest dam of the Near East and represents an important water storage for local human activities. The dam was built between 1981 and 1988 north of the village of Eski Mosul, submerging the course of the Tigris River for ca 100 km. The analysis of historical images derived from declassified Corona satellite imagery acquired between December 1967 and August 1968 reveals the pristine pattern of the Tigris River, including the seasonal changes of its riverbed, shifting across the hydrological year from meandering to anastomosing patterns. Geomorphological mapping based on Corona images allowed to estimate the seasonal modification of fluvial elements such as the floodplain and point, middle, and longitudinal bars. The comparison with Landsat data collected since the 1990ies showed the first phases of the basin filling and the control on the present-day aspect of the lake inherited from the setting of the Tigris channel belt and, more in general, the litho-structural control over the evolution of the local hydrographic network. Moreover, we document the influence of the original Tigris course on its recent insertion into the lake. Our work allowed to reconstruct the ancient fluvial landscape below the Mosul Dam Lake and the evolution of its riverscape controlled by litho-structural factors and seasonal variations of the river discharge, demonstrating the importance of old aerial/satellite imagery in interpreting natural geomorphic processes today altered by human agency.