Evolution of fluvial environments and history of human settlements on the Ticino river alluvial plain

The present contribution aims to provide better knowledge on the evolution of the fluvial environments of the Ticino river alluvial plain, highlighting the complex interaction of the Ticino river and its lateral tributaries with the human communities since the Neolithic. The study considers information derived from historical sources, from previous research on three sites based in the Ticino river floodplain and from data of six archaeological sites located on four alluvial fans. For the investigated sites the analyses of the lithostratigraphy and the archaeological evidence were constrained with radiocarbon dating, providing the interpretation of the depositional context of the studied sequences and their correlation with the cultural periods and epochs defined for the southern Swiss Alps. The combined approach allowed for the definition of 13 phases of enhanced hydro-sedimentary activity from the Neolithic to the contemporary period. The possible palaeoenvironmental and palaeoclimatic causes, as well as the impacts of these phases on the human settlements, are discussed.

Flash Flood Susceptibility Evaluation in Human-Affected Areas Using Geomorphological Methods—The Case of 9 August 2020, Euboea, Greece. A GIS-Based Approach

Flash floods occur almost exclusively in small basins, and they are common in small Mediterranean catchments. They pose one of the most common natural disasters, as well as one of the most devastating. Such was the case of the recent flood in Euboea island, in Greece, in August 2020. A field survey was accomplished after the 2020 flash floods in order to record the main impacts of the event and identify the geomorphological and man-made causes. The flash flood susceptibility in the urbanized alluvial fans was further assessed using a Geographic Information System (GIS)-based approach. Our findings suggest that a large portion of the alluvial fans of Politika, Poros and Mantania streams are mainly characterized by high and very high hazard. In fact, ~27% of the alluvial fans of Politika and Poros streams are characterized with very high susceptibility, and ~54% of Psachna area. GIS results have been confirmed by field observations after the 2020 flash flood, with significant damages noted, such as debris flows and infrastructure damages, in buildings, bridges and the road networks. In addition, even though the adopted approach may be more time-consuming in comparison to purely computational methods, it has the potential of being more accurate as it combines field observations and the effect of past flooding events.

How Young is a 300-Year-Old Wetland? The Case of the Pantanal Marimbus, Chapada Diamantina, Brazil

The Chapada Diamantina, in Northeastern Brazil, is one of the few places where one can find drylands with a backswamp containing hundreds of dead deciduous trees in the floodplain. During the 18th century, the region was globally important due to the exploration of mineral resources. The death of these trees was caused by mining activities that silted the main river, leading to the impoundment of the tributary river, and resulting in a wetland known as Pantanal Marimbus, having as indicators: (i) backswamp morphological feature that remains permanently flooded in the axis of the fluvial course, and (ii) alluvial fans concentrated in one footslope area where mining activities at the Chapada Diamantina were also concentrated. The hydrological and sedimentological behavior was investigated to multi-methods. By analysing four different samples from the bark and core of the same tree, we obtained calibrated radiocarbon dates within the 18th century. For no robust dendrochronology could be performed, a simple sequence model was built, revealing a high probability that the tree lived until approximately 1700 AD. 14C-AMS measured pioneering possible to evaluate the 300-years-old wetlands juvenile evolutionary state.