Interplay between climatic, tectonic and anthropogenic forcing in the Lower Rhine Graben, the Roer River

Abstract The Roer is a small river which drains the Rhenish shield and confluences with the Meuse River. Up to now the geological, climatological, biostratigraphical, and pedological setting of the Roer Valley were not sufficiently integrated to disentangle the effects of external forcing factors on the Roer River. In this study we perform a detailed and integrated reconstruction of the fluvial morphology and palaeogeography of the Roer River in order to determine responses to combined climatic, tectonic and anthropogenic forcing factors. The Roer River has formed five terrace levels since the Weichselian Late Pleniglacial. Fluvial planform of the Roer River was predominantly climate-controlled during the Lateglacial and Early Holocene. Reach-to-reach variations in river terrace formation and fluvial planform change occur due to variations in tectonic setting, subsurface geology, base-level fluctuations and the confluence with tributary systems. Differential subsidence by active faulting in the Roer Valley Graben during the early Lateglacial caused a preferential usage of the down-tilt channels of the, up to then, double channel belt systems in the Roer Valley. This preferred channel avulsion towards a fault zone, leaving an underfit system on the up-tilted side, and the clustering of Holocene Roer channels along that fault zone, meet the criteria for a lateral response of the Roer River to a tectonic forcing. Anthropogenic influences in the form of deforestation and land-use changes during the Late Holocene are responsible for the formation of a final terrace level and overbank sediments.