Landform-driven human reliance on rivers in imperial China

Proximity to rivers and flat areas are two of the main factors that determine the location of human settlements. Despite empirical relationships between human settlements, river dynamics and the corresponding landforms, the underlying mechanism remains speculative. Here, we present the first millennium-scale, quantitative tem-poral analysis of human population dynamics and its relationship with river location and landforms in imperial China across four dynasties (Han - 2 CE, Tang - 742 CE, Song - 1102 CE and Ming - 1522 CE) over the last 2000 years. Our results show less human reliance (measured by the number of people living close to a water course) on rivers for people living in lowland areas, which we interpret to be related to flood risk and the availability of groundwater from alluvial aquifers distant from rivers, used for agriculture. Conversely, people living in mountainous and hilly areas appear to have a stronger reliance on rivers in imperial China. Specifically, behind the strong variations of human-river relation across millennia, we infer a general principle highlighting the role of landforms in human-river interactions. These results shed light on how geomorphology shape settlement and urban patterns, with important implications for sustainable lifeways in riverine environments.