Mapping the Depths: Sonar Prospection of the Trajan’s Pontoon Bridge at Lederata (the Danube Limes)

Abstract

The research presented focuses on investigating the Trajan Pontoon Bridge, which once connected the Roman fortresses of Lederata and Sapaja across the Danube. Constructed at the beginning of the First Dacian War, this bridge played a crucial role in facilitating the movement of Roman troops into enemy territory. The study utilizes sonar prospection, marking the first application of this technology in Serbian archaeology, and aims to map submerged remains to confirm the bridge's location and identify its structural elements. Conducted within the framework of the SEED project for young researchers at the Institute of Archaeology in Belgrade, this research seeks to integrate advanced hydrographic survey techniques with traditional archaeological methods. The sonar investigation has the potential to reveal the exact positions of the bridge's wooden anchoring pillars, which supported its floating sections, offering new insights into the engineering strategies employed by the Romans during the early 2nd century AD. This underwater exploration will provide crucial empirical data for understanding the spatial distribution of Roman military architecture along the Danube. A multidisciplinary approach, combining sonar data with historical and epigraphic sources, sets a precedent for future underwater archaeological research in Serbia. The methodological approach and findings from this research will hopefully advance our understanding of Roman military logistics and underline the importance of sonar prospection for archaeology. Sonar is the only viable method for studying Roman underwater architectural remains along the middle Danube limes due to the limited water clarity and the impact of two massive dams constructed in the Iron Gates gorge, which submerged many ancient sites