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

Experimentelle Rinnenerosionsforschung vs. Modellkonzepte – Quantifizierung der hydraulischen und erosiven Wirksamkeit von Rinnen
Rill experiment:
The objective of the rill experiment is to simulate concentrated runoff without the effect of
splash or additional inflow into a rill. Each experiment consists of two runs: first the rill is
tested under dry conditions; in a second run, about 15 min later, the same rill is tested under
wet conditions.
With a motor driven pump, a constant discharge of 9 l min -1 is maintained during 8 minutes,
resulting in a total water inflow of 72 l.
In order to reduce the flow velocity of the inflowing water and consequently avoiding the
mobilization of soil material at the starting point, the water inflow is initiated through the
“Field-Adapter-Tool A” (FAT-A) (Fig.4). This is a longish 55x30 cm plastic plate on which
plastic pipes and an inverted meadow of synthetic turf are fixed. The hose can be adapted to
the pipe system with a compressed air adapter. The flow velocity is firstly reduced by the
course of the pipes and secondly by the flow path under the artificial turf. In this way,
accelerated erosion can be avoided, as the water leaves the plastic plate through a cut and
flows into the rill in a rather 'natural' speed.
Fig.4: Device for water inflow into the rill (Fat-A).
The travel time of the waterfront and of two colour tracers are measured for each meter using
a chronograph. The first colour tracer is induced after three minutes at the starting point, the
second follows after six minutes. By means of this procedure, three velocity curves are
recorded and changes in flow dynamics can be detected. As colour tracers, food colourings (E
124 (red) and E 13 (blue)) are used for reasons of safety.
The experiment ends after 25 m flow length. For the continuous measurement of the water
level by means of a pressure transducer (Ecotech DL/n, V2.35), the FAT-Z (Fig. 5) has been
designed. It consists of a metal sheet with a plastic drainpipe with a junction. The sheet is
driven into the ground as far until the opening of the drainpipe is on rill’s ground level. The
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