The impact of pre-historic land use on suspended sediment delivery to the floodplains in he Rhine valley and delta: catchment-scale quantifications and the nature of response

Abstract

The non-alpine Rhine catchment has a long history of human occupation and — especially from the Neolithic onwards — the landscape has been increasingly altered by human cultivation. This most likely influenced erosion and subsequently sediment delivery to the fluvial system. Increased sediment input as a result of human land use has been documented in smaller tributaries of the Rhine, but has so-far not been quantified on a catchment scale. This study quantifies the amounts of floodplain sedimentation per millennium for natural and human-impact time scales (the last 9000 years) for three large floodplain areas that have functioned as sediment sinks: the northern Upper Rhine Graben, the Lower Rhine Embayment and the Rhine-Meuse delta. New collected field data and borehole data from extensive databases, and C-14 and OSL dates allow calculating thicknesses, volumes and ages of the floodplain sediments. The results show remarkable coherent trends for different parts of the drainage basin: increased sediment delivery during the late Holocene caused raised overbank sedimentation by up to 60 % when compared to the pre-human impact time interval in all study areas.