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

Experimentelle Rinnenerosionsforschung vs. Modellkonzepte – Quantifizierung der hydraulischen und erosiven Wirksamkeit von Rinnen
Generally we could distinguish between seven different sediment concentration curves
(Figure 4-7). (1) The first trend was defined by a decrease from the first to the last sample,
only one sample with increasing value disturbed this trend. This form was found in 1a1, 1a2,
1b1, 2a2, 2a3 and 3a3. (2) In the second form, the decreasing trend was not disturbed by any
increasing value. This trend was shown by 1a3. (3) The next trend type was defined by an
increase from the first to the second sample, after that, the values remained almost constant:
1b2, 2b1, 3a1, 3b1, 3b2, 3b3, 4a2, 4b1, 4b2, and 4b3. (4) It was also possible that the values
stayed about constant from the first to the last sample, this form was found in 1b3 and 4a3. (5)
In 2a1, the values increased from sample 1 to sample 3, after that the value decreased at
sample 4. (6) In version 6, we observed a decrease from sample 1 to sample 2 and an increase
from sample 2 up to sample 4. This was found in 2b2, 3a2 and 4a1. (7) The last version found
at 2b3 showed a decrease from sample 1 to sample 2 followed by a constant trend which was
disturbed by one sample with increasing value.
Flow velocities along the rill profile
In experiment 1 and 4, the flow velocity curves showed similar forms: In the first runs, the
two tracers are similar over the rill profile; the water front didn’t reach the same velocity. In
run 2, the velocity of the waterfront increased and tracers and water front showed similar
values. In experiment 3, the differences between the tracers and the front were also low in the
second run, but the roughly parallel trend of the tracers in run 1 was disturbed in run 2. In the
first run of experiment 2, the tracers showed similar values, the waterfront showed lower
values again. But in run 2, the water front showed a very irregular trend with fewer
similarities to the tracer curve. Because of technical problems, the velocity of tracer one in
experiment 2b was not measured.
Runoff values at the end of the tested rill part
In most cases, the increase of the runoff curve is very fast, only run 1 in experiment 1 showed
a slower increase. In all cases, the runoff in run 1 started later as in the second run and the
values were lower, this difference was very noticeable in the first experiment. Also the runoff
duration was longer in the second runs of all experiments. Because of technical problems, the
runoff of run 1 in experiment 4 was not measured but the observations confirmed the
measurements of the other experiments.
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