A sediment budget for a forested catchment in Luxembourg and its implications for channel development

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Abstract
In the forested catchments of the Luxembourg Keuper area, deeply‐incised valleys have developed in which streambank erosion is a widespread phenomenon. For one of the catchments in this area, the Schrondweilerbaach catchment, a sediment budget was constructed in order to determine the relative contributions of the various channel and valley slope processes to sediment output.Streambanks contributed 53 percent of the output with bank scour and subsoil fall being the main processes while to a lesser extent bank material was supplied by bank failures, splash erosion, and soil creep. The remaining 47 per cent of the sediment was derived from the valley slopes mainly through the combined action of rainsplash detachment and overland flow transport. During the two years of investigations sediment output from the drainage basin almost equalled sediment input from streambanks and valley slopes. The results of the measurements of the various streambank processes are integrated in a descriptive model for the present‐day widening of valley incisions in the study area and used to hypothesize the palaeohydrological development of the basin. Special attention is paid to the (in)direct effects of the forest vegetation on streambank erosion and sediment transport through the stream channel.