Differentiated fluvial and environmental responses of trunk and tributary systems to Lateglacial and Holocene climate change

The geomorphic development of major rivers and smaller tributaries in response to climatic and environmental changes has been studied intensively in the past. However, impacts on confluence regions, with tributaries, have rarely been investigated. We aim to explore the similarities and differences in fluvial development over the last glacial to interglacial transition in the confluence area of the Meuse and the Loobeek in the southern Netherlands. We established five coring transects to investigate the fluvial architecture and sedimentary environments of the systems. Pollen analyses and radiocarbon dating enabled to establish the regional and local vegetation and the palaeogeographic evolution. The fluvial responses of the large Meuse and small Loobeek are strongly different and depend on differences in discharge, sediment supply and vegetation development. The fluvial response to the early Lateglacial warming is rapid in the small tributary and more delayed in the large-scale system. Smaller or shorter climate changes (during the Younger Dryas) are not registered in the channel pattern of the small-scale system. An anastomosing or diffuse drainage pattern and peat formation characterise the brook system during most of the Holocene, in contrast to the meandering Meuse system.