Freiburger Geographische Hefte, Vol 65

Summary

In the Black Forest the onset of continuous settlement and agricultural activities only started during medieval times. In the last millennium human influence let to various changes of the landscape, but the triggered geomorphodynamical processes in the higher areas of the Black Forest are rarely studied so far. The aim of the research project was to investigate the relief shaping due to human activity and to compile an environmental and land use history of the middle Black Forest. The research project was conducted as part of the DFG Postgraduate Research Group “Formation and Development of Present-Day Landscapes” at the University of Freiburg, Germany.

The study area is located at the main European watershed and comprises the very different relief and drainage pattern of the Danube and Rhine rivers, which enables a comparison and comprehensive evaluation of anthropogenic influence on the relief.
Different geo- and bioarchives were investigated using geomorphological and geophysical methods, complemented by pollenanalysis and anthracological (charcoal) studies. By radiocarbon dating stratigraphic units were further allocated and sediments correlated with different phases of land use. Besides the study of environmental archives historical maps and old aerial photographs were evaluated to document landscape changes. The results of the research project document the great benefit of this multidisciplinary approach.

The earliest detected human impact in the study area dates back to the late Roman period (after the abandonment of the limes), but had had little neither lasting nor extensive effect on the relief. For the Early and High Middle Ages the geoarchives as well as the mires show a first systematic land cultivation and colonisation of the area – earlier than assumed by historians. The intense land use caused geomorphic processes with erosion of periglacial sediments from the slopes and incision of streams at the valley grounds on the one hand and accumulation of colluvial sediments and flood loams on the other hand.
Today only the lowermost part of the solifluction layers can still be found extensively in the study area while the two upper layers are missing widely. In the following centuries until the 19th century, soil erosion due to agricultural techniques still remained intense and resulted in further colluvial sediments and flood loams. Especially the High Middle Ages and the 18/19th century AD can be regarded as main periods of geomorphodynamic activity. The later period is associated with vast woodland clearings with a remaining overall woodland area of only 17 %, as documented by historical maps. Besides there were periods of relative geomorphological tranquillity, which go along with phases of lower land-use intensity like the Late Middle Ages or the time while and after the Thirty Years’ War.

Even though the woodland widely recovered in the last two centuries, minor anthropogenic impacts are still causing severe relief changes, as documented by the development of a gully at the study side “Hexenloch” and by the land slide in the “Rohrbachtal”. In regard to the predicted rise of intense rainfall events in the Black Forest due to global climate change a destabilisation of the widespread loose sedi-ments may occur.