Large Rivers, Small Rivers: Paleogeographic Evidence for Flood Memory and Settlement Strategies in Chalcolithic Communities of the Lower Danube Plain

The spatial distribution of Chalcolithic settlements in the East Lower Danube Plain (SE Romania) shows markedly higher densities along small river valleys with low modern discharges, such as the Călmățui, Mostiștea, and Teleorman, which originate in the upper plains (150–300 m a.s.l.). In contrast, valleys of larger Carpathian-sourced rivers (e.g., Buzău, Ialomița, Argeș), host far fewer settlements. Our research explores whether these patterns reflect deliberate site preferences, possibly influenced by cultural memory of past fluvial and marine flooding, or whether they result from fluvial erosion that may have erased significant parts of the archaeological record. New chrono-stratigraphic data are used to reconstruct the paleo-hydrology and floodplain dynamics of the lower Danube and its tributaries, with a particular focus on the Călmățui valley, a key prehistoric habitation region connecting the Subcarpathians to the Danube lowlands and Dobrogea. Elevated fluvial features, such as terraces, point bars, and remnant islands, were preferentially inhabited. By comparing floodplain remnant islands along the Călmățui with those in adjacent large-river valleys, we assess whether Chalcolithic populations consistently favored small river systems. Our results support a major Mesolithic avulsion, through which the small Călmățui River occupied the abandoned paleo-Buzău valley. Reconstructed floodplain dynamics (aggradation), macrocharcoal records, and stratigraphy reveal divergent rates of landscape change between large and small rivers during main phases of human occupation. Settlement analyses using long-term habitation on floodplain remnant islands show that Chalcolithic communities concentrated along small rivers, likely due to their lower flood risk and greater stability. This behaviour, though strongest in the Chalcolithic, may have originated in the Neolithic, suggesting a long-lived tradition of flood-averse settlement planning that diminished after the onset of the Bronze Age.