English Abstract The supply of sediment to the drainage network of the
River Rhine is estimated for present-day climate and land use. A
distributed model was developed, which would enable us to identify areas
that actively deliver sediment to the drainage system, assuming soil erosion
on hill slopes to be the primary sediment source. The amount of mobilised
sediment that actually reaches the stream network depends on the proximity
of the sediment source to the stream, the occurrence of overland flow and on
the character of the flow path. The sediment supply model makes use of a
GIS database containing information about relief/morphology, soil, land use
and the drainage network, and is linked to the RHINEFLOW model. The results
show that for present-day conditions, sediment supply is high during late
spring and early summer and low later in the growing season and in the
winter months. Sediment production is highest in periods when severe rain
falls on unprotected soil. The temporal pattern in the sediment supply is
largely determined by the course of the rainfall erosion and crop growth
stages during the year. The temporal pattern of basin sediment yield is not
related to the timing of sediment supplied by soil erosion, but governed by
the discharge regime. This suggests that suspended sediment is stored in
the alluvial system in the summer and removed during the runoff season.
Furthermore, a large part of the sediment produced in the Alps and in the
Swiss middle mountains is stored in the alluvial system further downstream
where stream power decreases.