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

Sediment budgeting concepts serve as quantification tools 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, such quantification approaches are rarely applied in geoarchaeological studies. The case of Charlemagne's summit canal (also known as Fossa Carolina) and its erosional collapse provides an example for which we can use this geomorphological concept and understand the abandonment of the Carolingian construction site. The 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 river systems. According to our dendrochronological analyses and historical sources, the excavation and construction of the Carolingian canal took place in AD 792 and 793. Contemporary written sources describe an intense backfill of excavated sediment in autumn AD 793. This short-term erosion event has been proposed as the principal 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 the erosional 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. The exceedance of the manpower tipping point may have caused the abandonment of the entire construction site. The spatial distribution of the dendrochronological results indicates a north–south direction of the early medieval construction progress

Agricultural Landscapes: History, Status and Challenges

Agricultural landscapes (rural landscapes, agrolandscapes) are territories shaped by agricultural production. They have enabled the development of human civilizations and are a cultural achievement. Peasants, farmers and agricultural enterprises feed society. They have created agricultural landscapes for their business and habitats for their life. To understand transformation processes in agricultural landscapes, we analyse the history of agriculture with a special focus on Europe and Eurasia. Current agricultural landscapes in a crowded, globalized world are multifunctional, highly complex systems. They not only serve to produce food commodities and energy for the increasing and expanding urban population but also provide diverse ecosystem services and need to cater for the demands of the rural population. Current agriculture is highly productive in wealthy countries, but due to high inputs it is also responsible for environmental problems such as water pollution and loss of biodiversity. Industrial-style agriculture in large fields has resulted in increased productivity but simplified the structure of landscapes and eliminated elements of nature and rural culture. Major problems that urgently need to be addressed include trends towards disrupting natural cycles in agricultural production, soil and water degradation, ageing populations in villages and the breakdown of rural infrastructure. Agricultural landscape research provides analyses to understand these processes and helps elaborate sustainable scientific, technical and cultural solutions