A new method is used to estimate the volumes of sediments of glacial
valleys. This method is based on the concept of sloping local base
level and requires only a digital terrain model and the limits of
the alluvial valleys as input data. The bedrock surface of the glacial
valley is estimated by a progressive excavation of the digital elevation
model (DEM) of the filled valley area. This is performed using an
iterative routine that replaces the altitude of a point of the DEM
by the mean value of its neighbors minus a fixed value. The result
is a curved surface, quadratic in 2D. The bedrock surface of the
Rhone Valley in Switzerland was estimated by this method using the
free digital terrain model Shuttle Radar Topography Mission (SRTM)
(~92 m resolution). The results obtained are in good agreement with
the previous estimations based on seismic profiles and gravimetric
modeling, with the exceptions of some particular locations. The results
from the present method and those from the seismic interpretation
are slightly different from the results of the gravimetric data.
This discrepancy may result from the presence of large buried landslides
in the bottom of the Rhone Valley.