Evolution of fluvial environments and history of human settlements on the Ticino river alluvial plain (Southern Switzerland)

Understanding the past river dynamics, their relationship with the climate oscillations, and their impact on humans as a resource and/or natural risk, is very crucial. In recent times many studies were carried out to determine the evolution of the hydro-sedimentary dynamics of Alpine rivers in the past, trying to predict the future effect of the increased fluvial activity leading to repeated floods, especially in the current context of climate change.

The present contribution is the object of a recent publication (Czerski et al. 2022, Geogr. Helv. 77) on the evolution of the fluvial environments of the Ticino river alluvial plain (Southern Switzerland). The research is based on historical sources, previous investigations on three sites based in the Ticino river floodplain, and data collected on six archaeological sites located on four alluvial fans. The results revealed a complex interaction of the Ticino river and its lateral tributaries with the human communities since the Neolithic (5400–2200 BCE). The lithostratigraphy and the archaeological evidence described on the field were constrained by radiocarbon dating, providing the interpretation of the depositional context of the studied sequences and their correlation with the geological epochs and the cultural periods defined for the Southern Swiss Alps. The combined approach allowed for the definition of 13 phases of enhanced hydro-sedimentary activity covering a period between the Neolithic and the contemporary period. The palaeoenvironmental and palaeoclimatic causes of these phases and their impacts on the human settlements are evaluated.

Most of the enhanced hydro-sedimentary phases could be linked to the regional or continental palaeoenvironmental and palaeoclimatic context, recorded in correspondence with periods of climate degradation with the establishment of cold and humid conditions, evidence of glacier advances in the Swiss Alps, and/or by an increase in the flood activity on the southern side of the Alps. The more recent phases, in particular, are attributed to the coldest and moistest phases of the Little Ice Age (LIA) climate oscillation. The collected data allowed us also to assess the impacts of these enhanced alluvial phases on the human communities and to explain many of the sedimentological and archaeological observations on the field. For example, the torrential events attributed to the LIA had a strong impact on the construction and destruction phases observed for the archaeological site of Giubiasco Palasio.

The study is still ongoing; the summary on the evolution of the hydro-sedimentary dynamics of the Ticino river and its tributaries presented herein will be continuously refined and updated with further sedimentological and archaeological observations.