Forschungen zu den mittelalterlichen Binnenhäfen zwischen Rhein und Donau. In: Christoph Mielzarek/ Christian Zschieschang (Hrsg.), Usus aquarum. Interdisziplinäre Studien zur Nutzung und Bedeutung von Gewässern im Mittelalter (Köln/Weimar/Bonn 2019), 205-245.2019
Summary Research on Mediaeval Inland Harbours between Rhine and Danube This paper presents ongoing and completed research within the framework of the „Inland Harbours Project“ at Jena University. Five case studies – Karlburg, Salz, Ratisbon, Frankfurt on the Main, and the Fossa Carolina – illustrate how archaeological, geo-archaeological, and historical methods can help to identify harbour structures and historical riverbanks as well as transport networks. Previous work on mediaeval navigation was usually focussed on maritime harbours as well as early mediaeval emporia and often lacked interdisciplinary approaches. Because inland waters and especially rivers may have changed their course dramatically throughout history, it is essential to combine archaeological and historical methods and sources with geo-archaeological and other natural scientific methods. This enables the accurate reconstruction of the historical terrain relief and hydrological situations and correct interpretation of potential archaeological features of harbour installations. Additionally, the meaning and function of a harbour can only be understood by studying its location on a local scale within its related urban topography and harbour-related infrastructure (e. g. castles), and on a regional and superregional scale within its topographical and political framework. Research within the „Inland Harbours Project“ shows that even in the High and Late Middle Ages, harbours did not necessarily need constructive installations to land boats, which leads to the question of whether bank revetments and quays were initially a response to land reclamation. The two early mediaeval centres of Karlburg on the river Main and Salz at the Frankish Saale illustrate how methods of archaeology and geo-archaeology can be combined to receive evidence-based results of the former river courses and the terrain. For Karlburg, the hypothesis of a mediaeval harbour basin, which is based on a historical map from the 19th century, has been revised. The results of archaeological excavations, geological drillings, and surveys allowed the location of the mediaeval river bank at a distance of 2 km up to 100 metres west of the modern river. Because no harbour constructions were found, a natural landing site can be assumed. In contrast to Karlburg, a wide range of geo-archaeological methods showed the stable position of the Frankish Saale in Salz from the Neolithic to the Early and High Middle Ages. Being part of the royal palace complex Salz, located in the deserted riverine settlement Mühlstatt, people lived on an elevated, flood-safe position on a calcitecemented gravel layer/alluvial fan. A simple, naturally formed landing site with a gently sloping embankment could be reconstructed. The ongoing research of the mediaeval harbour in Ratisbon is focussed on the analysis of different small rescue excavations along the modern river bank and the analysis of a huge urban excavation at Regensburg „Donaumarkt“. Because of the excellent preservation of archaeological features, many scientific methods such as dendrochronology, radiocarbon dating, archaebotany, and archaeozoology are used to analyse the development of the mediaeval waterfront in light of inland navigation Forschungen zu den mittelalterlichen Binnenhäfen zwischen Rhein und Donau 245 and urban development. Early results of the Donaumarkt excavation revealed that the river bank from the 9th and 10th century was located 20 metres further inland. Moreover, a navigable side arm or canal was detected parallel to the main arm of the Danube that was used until the 11th or 12th century. In contrast to Karlburg and Salz, different types of bank revetments have been documented such as wattle work, stones, and wooden poles. The whole Danube river bank was used for navigation and may have had special functional zones that were associated with the landward urban topography. An exceptional example for the construction of mediaeval inland harbours is a quay wall of the 13th/14th century that was discovered in 2012 at the mediaeval Saalhof castle in Frankfurt on the Main. The quay made of stone and wood is located at the court wall of a mediaeval water castle from the 12th and 13th century (the Saalhof). The quay is two metres wide and paved, and it ran parallel to the court wall of the Saalhof. Based on urban topography, the Saalhof castle was located in the commercial heart of the town, framed by the most important streets. The Saalhof castle worked as a seat of royal and later civil administration. Because of its location on a natural alluvial land tongue that reached several metres into the river Main, it was suitable for controlling navigation and trade. With regard to the water castle of Kaiserswerth on the Rhine, the function of water toll collection is discussed. Mediaeval castles seem to have been of great importance to delineate royal territory and to control and defend important trade routes for inland navigation. The rivers Danube and Main remain among the most important routes for inland navigation today. Attempts to connect both river systems to bridge the European watershed were carried out in the Early Middle Ages by Charlemagne in 793 AD, who initiated an ambitious canal project – the Fossa Carolina. Written sources describe building the canal in detail as well as its failure. The constructive details of the threekilometre long canal and the question of its completion are the focus of an ongoing project, „Fossa Carolina“, which combines archaeological and geo-archaeological methods. Fieldwork showed that huge parts of the canal were buried under colluvial sediments shortly after the digging, and they were never removed afterwards. Together with the canal’s missing southern connection to the river Altmühl, this suggests that the canal was really never finished. However, at least some parts of the approximately five-metre wide canal fairway were ready to use and may have been navigable. The banks of the canal were fixed with wooden embankments to prevent erosion. The shallowest water depth was approximately 0.5 metres, which would have allowed navigation by early mediaeval flat-bottomed ships.