Quantum Systems

Sediment budgeting concepts serve as quantification tool to decipher the erosion and accumulation processes within a catchment and help to understand these relocation processes through time. While sediment budgets are widely used in geomorphological catchment-based studies, there is a lack of quantification approaches in geoarchaeological studies. The case of Fossa Carolina and its colluvial collapse can act as an example to use this geomorphological concept and understand the construction site abandonment. Charlemagne’s summit canal (also known as Fossa Carolina) is one of the largest hydro-engineering projects in Medieval Europe. It is situated in Southern Franconia (48.9876 N, 10.9267 E; Bavaria, Southern Germany) between the Altmühl and Swabian Rezat rivers, It should have bridged the Central European watershed and connected the Rhine-Main and Danube catchments. According to our dendrochronological analyses and historical sources, the excavation and construction of the Carolingian canal took place in 792 and 793 AD. Contemporary written sources describe an intense backfill of excavated sediment in autumn 793 AD. This short-term erosion event is supposed to be the reason for the collapse and abandonment of the hydro-engineering project. We use subsurface data (drillings, archaeological excavations and direct-push sensing) and geospatial data (a LiDAR Digital Terrain Model (DTM), a pre-modern DTM and a 3D-model of the Fossa Carolina) for the identification and sediment budgeting of the backfills. Dendrochronological findings and radiocarbon ages of macro-remains within the backfills give clear evidence for colluvial collapse of the canal project during or directly after the construction period. Moreover, our quantification approach allows the detection of the major sedimentary collapse zone. Here, the largest total amount of backfill sediments appears in the Central Section that might result in an abandonment of the construction site. The spatial distribution of the dendrochronological results indicates a direction of the early medieval construction progress from North to South, respectively from the Northern canal-tributary intersection to the Central European Watershed.