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

Experimentelle Rinnenerosionsforschung vs. Modellkonzepte – Quantifizierung der hydraulischen und erosiven Wirksamkeit von Rinnen
2.2 Methods:
All experiments were run on test plots with similar footprints (see fig. 2), installed in contour
line direction, but carried out on sites with differing surface properties and slopes. The test
plots are representative for areas used as pasture.
15 goats were guided over each test plot several times. Meanwhile, translocated material was
collected and the transport direction recorded. Surface type, slope and running speed were
varied in accordance with the observed way of natural flock movement patterns. The used
‘Malaga-goats’ (DOPPELBAUER 2002) and sheep weighed between 45 and 50 kg each. In
detail, we conducted the following experiments:
Experiment 1: Translocation quantity in down-slope direction
Experiment 1 was conducted on slopes of 8.5°, 12° and 20°. Vegetation cover was less than 5
% on the plots. Plot size was 2 m x 1 m (see fig. 2a). A Gerlach trough with the length of 2 m
was implemented as a sediment trap at the down-slope end of the plot. 15 goats were guided
over the plot 4 times in a row (= 60 goats). Afterwards, the sediment traps were emptied and
weighed. This process was repeated 10 times in order to simulate the impact of the passage of
a flock of 600 animals. In experiment 1c (slope 20°) we increased the running speed of the
animals after the 5 th run (= 5 x 60 goats), in the other 2 versions, the running speed was kept
constant over all runs.
Experiment 2: Translocation quantity parallel to contour lines
Experiment 2 was conducted on a 8.5° steep sheep trail. The test plot was covered with 13 %
vegetation and 18 % rock fragments. The footprint of the experiment was a combination of
two separate plots (each 2 x 1 m) resulting in a total size of 4 x 1 m. The Gerlach troughs
(each 1 m in length) were placed at a right angle to the moving direction of the goats at the
end of those plots (see fig. 2b). Again, the material collected in the troughs was weighed after
each run of 60 goats. In experiment 2a, the running speed of the goats was increased after the
5 th run, in experiment 2b the speed was kept constant.
Experiment 3: Translocation direction and distance of rock fragments
Experiments 3 a, b and c were conducted on test plots of 2 x 0.6 m (1.2 m 2 ) on 4° (3 a & 3 b)
and 11° slopes (3 c). On all plots 120, colored and numbered rock fragments (ø ca. 3 cm)
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