The determination of sediment storage is a critical parameter in sediment
budget analyses. But, in many sediment budget studies the quantification
of magnitude and time-scale of sediment storage is still the weakest
part and often relies on crude estimations only, especially in large
drainage basins (>100km2). We present a new approach to storage quantification
in a meso-scale alpine catchment of the Swiss Alps (Turtmann Valley,
110km2).
The quantification of depositional volumes was performed by combining
geophysical surveys and geographic information system (GIS) modelling
techniques. Mean thickness values of each landform type calculated
from these data was used to estimate the sediment volume in the hanging
valleys and the trough slopes. Sediment volume of the remaining subsystems
was determined by modelling an assumed parabolic bedrock surface
using digital elevation model (DEM) data.
A total sediment volume of 781·3×106?1005·7×106m3 is deposited in
the Turtmann Valley. Over 60% of this volume is stored in the 13
hanging valleys. Moraine landforms contain over 60% of the deposits
in the hanging valleys followed by sediment stored on slopes (20%)
and rock glaciers (15%).
For the first time, a detailed quantification of different storage
types was achieved in a catchment of this size. Sediment volumes
have been used to calculate mean denudation rates for the different
processes ranging from 0·1 to 2·6mm/a based on a time span of 10ka.
As the quantification approach includes a number of assumptions and
various sources of error the values given represent the order of
magnitude of sediment storage that has to be expected in a catchment
of this size.