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

Experimentelle Rinnenerosionsforschung vs. Modellkonzepte – Quantifizierung der hydraulischen und erosiven Wirksamkeit von Rinnen
All three erosion parameters showed higher values in the experiment with goat trampling, but
the difference is most obvious in the dry run. In the second (wet) run, the values were equal or
at least similar to the values of the experiments without trampling. Transport and detachment
rate were about 5 times higher in the dry run with goat trampling as in the runs without
trampling. Sediment concentration in the dry run with trampling was about 2.5 higher
compared to the experiment without trampling (see figure 8).
Interpretation:
The rill experiment clearly shows the short-term influence of goat trampling. Livestock’s
hooves’ impact prepares the soil surface and a large quantity of loose material is made ready
for transport (see experiment 4). Crucially, this material is removed very fast; the second run
with trampling still shows nearly the same values as the runs without preceding trampling.
The sediment concentrations at the waterfront were clearly higher in the experiment with
trampling, whereas the other samples show similar concentrations. Accordingly, trampling
provides a large quantity of loose material but its impact on mobilization is only detectable for
a short time.
3.6 Statistical analysis
In table 1, the statistical values of the experiments 1, 2 and 4 are summarized. In experiment 1
and 2, the first run was not used in the calculations to avoid mistakes caused by the
installation of the troughs. The difference between mean and standard deviation increases
with slope, meaning high quantities as well as low quantities of substrate can be translocated.
The quantity of the mean increases with slope but the values become less stable. This is also
detectable in figure 8. Regarding the values for the movement parallel to contour lines, the
differences between mean and standard deviation for trough 1 and 2 in each version are very
similar, they are in all three cases between 52 and 58 %. But in all three cases, the first trough
shows clearly higher differences than the second trough. Because of the low n-values, we do
not want to over-interpret the values and conclude that the high values for trough 1 are caused
by the jumping-in and -out of the animals at the beginning of the test plot. Once they are
inside the fenced course, the movements are smoother. Figure 9 shows that again, the fast
running speed can cause very high values as well as low values, the mean values are clearly
higher than under slow movement but the values are less stable. The high difference between
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