3D-Modelling of Charlemagne’s Summit Canal (Southern Germany)—Merging Remote Sensing and Geoarchaeological Subsurface Data

Abstract

The Early Medieval Fossa Carolina is the first hydro-engineering construction that bridges the Central European Watershed. The canal was built in 792/793 AD on order of Charlemagne and should connect the drainage systems of the Rhine-Main catchment and the Danube catchment. In this study, we show for the first time, the integration of Airborne LiDAR (Light Detection and Ranging) and geoarchaeological subsurface datasets with the aim to create a 3D-model of Charlemagne’s summit canal. We used a purged Digital Terrain Model that reflects the pre-modern topography. The geometries of buried canal cross-sections are derived from three archaeological excavations and four high-resolution direct push sensing transects. By means of extensive core data, we interpolate the trench bottom and adjacent edges along the entire canal course. As a result, we are able to create a 3D-model that reflects the maximum construction depth of the Carolingian canal and calculate an excavation volume of approx. 297,000 m3. Additionally, we compute the volume of the present dam remnants by Airborne LiDAR data. Surprisingly, the volume of the dam remnants reveals only 120,000 m3 and is much smaller than the computed Carolingian excavation volume. The difference reflects the erosion and anthropogenic overprint since the 8th century AD.

Sediment budgeting of short‐term backfilling processes: The erosional collapse of a Carolingian canal construction

“…The first challenge is the integration of all datasets to create a dense spatial network of backfill information. According to Schmidt et al (2019), our modelling approach combines the drilling results with high-resolution cross-section reference geometries (three archaeological excavation trenches, two direct push sensing transects). For the first time, we interpolate the upper and lower limit of the backfills derived from the drillings according to the respective canal geometry.…”

“…Similar to the 3D model with maximum excavation depth, due to the high-resolution reference cross-sections, the raster layer of the backfill sediment storage has a spatial resolution of 0.5 × 0.5m. Schmidt et al (2019) recently produced a 3D model of the backfill lower level, and estimated the maximum excavation depth with the same modelling approach. Quantitatively, we applied the sediment storage of the backfills through the subtraction of both 3D models.…”

“…Furthermore, we compile the radiocarbon ages of the backfills, and we determine the spatial distribution of dendrochronological data from the Early Medieval canal construction. Following the modelling approach of Schmidt et al (2019), we use the spatial data of the backfills and set up a quantitative model of the backfill sediment budget and, subsequently, of the collapse of the Early Medieval canal construction.…”

Genesis of magnetic anomalies and magnetic properties of archaeological sediments in floodplain wetlands of the Fossa Carolina

“…Bridging of the Central European watershed was of high geostrategic relevance, due to the expanding fluvial communication and transportation network of the Franconian Empire at that time (McCormick, ; Werther et al, ). Nevertheless, the canal was never finished (Kirchner et al, ) and only remains of it are visible today (Schmidt et al, ; Schmidt, Werther, & Zielhofer, ). The post‐Carolingian canal filling was reconstructed using excavation, drillings, and sediment analysis (Völlmer et al, ; Zielhofer et al, ).…”

“…The canal has a length of 2.9 km, as proven by drillings (Kirchner et al, ; Zielhofer et al, ), archaeological excavation (Werther et al, ), and direct‐push sensing (Hausmann et al, ; Völlmer et al, ). Furthermore, extensive multi‐disciplinary research has been carried out at the Early Medieval canal over the last decade (Ettel, Daim, Berg‐Hobohm, Werther, & Zielhofer, ; Hausmann et al, ; Kirchner et al, ; Linzen et al, ; Schmidt et al, ; Schmidt et al, ; Stele, ; Zielhofer et al, ). Therefore, the site offers an excellent case study.…”