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

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 per cent 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.

Luxembourg

“…For the forested Keuper marl areas, more data are available. Current erosion rates for small catchments are given by several authors (Imeson and Vis, 1984a;Van Hooff and Jungerius, 1984;Duysings, 1987). According to these authors, these small watersheds under forest show suspended solid outputs to be a factor 2-5 lower than for the agricultural watersheds on the same substratum, depending on the watershed studied.…”

“…However, for the catchments under agriculture, the chemical and mechanical erosion rates are about the same (Imeson and Vis, 1984a;Duysings, 1987).…”

“…(equalling approximately 0.05 mm of annual soil surface lowering) for the period 1979-81 (Duysings, 1987; Table 1.32.1). The values of slope denudation confirm the average rates given by Poeteray et al (1984) for the last 200 years (0.020-0.054 mm yr À1 ).…”

“…For partial areas, sediment yield is higher, with values between 2.0 and 1.45 t ha À1 yr À1 (Hendriks and Imeson, 1984;Cammeraat, 1992). Duysings (1987) established a very detailed sediment budget for one of the streams in the area showing the contribution of different sources and processes to the total budget of a 60.8-ha catchment (Fig.1.32.4). Soil erodibility was studied for different land uses in the same area (Imeson and Vis, 1984b).…”

Assinaturas topográficas humanas (ATH´S) no contexto dos canais derivados multifuncionais e suas repercussões hidrogeomorfológicas

“…Estudos hidrossedimentares se ocupam, principalmente, da quantificação e distribuição dos sedimentos produzidos, transportados e, por vezes, depositados em um sistema de drenagem (RICHARDS, 1982;SLAYMAKER, 2003 1978;DIETRICH et al, 1982;DUIJSINGS, 1987;PHILLIPS et al, 2000), como visto no item 4.3, intervenções humanas podem impactar as direções dos fluxos, promovendo, retendo ou atrasando o deslocamento dos sedimentos. Já este item busca avaliar a repercussão dos sistemas de derivação para as vazões e sedimentos.…”