Stefan Wirtz Vom Fachbereich VI (Geographie/Geowissenschaften ...

Experimentelle Rinnenerosionsforschung vs. Modellkonzepte – Quantifizierung der hydraulischen und erosiven Wirksamkeit von Rinnen
The rill experiment as a method to approach a quantification of rill erosion process
activity
Wirtz S. (1), Seeger M. (1,2) & Ries J.B. (1)
(1) Dep. of Physical Geography, Trier University (2) Dep. of Land Degradation and
Development, Wageningen University
with 9 figures and 6 tables
Summary
Within this paper a standardized method to quantify sediment transport and runoff in natural
rills is described. In order to achieve this, several rill experiments (RE) were accomplished in
March 2007 in the Arnás catchment in the Spanish Pyrenees. Both, anthropogenically
initiated and naturally developed rills were flushed with a total water quantity of 72 l in 8
minutes (equivalent to 9 l min -1 ). Following the developed experimental routine flow
velocities are recorded along the whole flushed rill, sediment concentrations are measured at
different points and different times during the experiment and runoff values are measured
after 25 m. For the characterisation of the rill, slope is measured and micromorphological
features like scours are registered.
By means of the developed rill experiments it becomes possible to assess the effectivity of
single rills in a catchment. However, the assessments can not be generalized because it is
impossible to project the behaviour of one rill to other rills, even if the spatial distance in
between is small. But it gets possible to detect the qualitative process activity in a rill.
The average slopes oscillated between 7.6° and 11.3°, the highest slope was 16°. The
sediment concentrations reached average values between 0.69 and 2.21 g l -1 , the maximum
values ranged between 1.59 and 6.31 g l -1 . Comparing the sediment concentrations measured
in the rills to the sediment concentrations in the runoff of the river Arnás, it can be stated that
the concentrations in the rills are usually higher.
Keywords: soil erosion, rill erosion, field experiments, quantification of process activity,
Arnás catchment
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