Metric-based analysis of the historical drivers of surface hydrological connectivity
Abstract. Hydrological connectivity is essential for the maintenance of important hydrological and ecological processes of catchments. Over time, human activities have altered the natural patterns of hydrological connectivity, leading to habitat loss and deterioration. Historical information from cartographic maps can be used to enhance our understanding of large-scale hydrological processes such as connectivity, by offering snapshots of past, less human-impacted landscapes and hydrological systems. The focus of this study is on historical surface hydrological connectivity and its landscape drivers (e.g., lithology, topography, land use/ land cover) in ten Swiss catchments from different biogeographic regions (i.e., Pre-alpine, Alpine, Karstic, Plateau), and with varying physiographic characteristics. We employed hydromorphological metrics derived from historical maps (~ late 19th century) as proxies of surface hydrological connectivity, with the main goal of identifying the primary landscape drivers of connectivity. As expected from theory, the historical patterns of hydrological connectivity in the studied catchments were mostly driven by landscape topography, and in particular by the slope and the morphology of the valley bottom. Unexpected relationships between connectivity and its drivers could be traced back to human practices, such as specific irrigation techniques and peat digging. Overall, our study shows how historical information can be employed to gain a deeper understanding on important large-scale hydrological processes, their primary drivers and on the history of human exploitation of the territory. Finally, this kind of approach paves the way for the characterization of how connectivity has changed through time.