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

Experimentelle Rinnenerosionsforschung vs. Modellkonzepte – Quantifizierung der hydraulischen und erosiven Wirksamkeit von Rinnen
fourth 2:30 min after the arrival of the water. The sampling disturbs flow behaviour, so it
should be taken quickly. There is no default quantity, but the sample should be enough for
filtration and determination of sediment concentration.
Laboratory analysis and data processing:
The samples are filtered with a 25 µm and a 2 µm pore size filter from Schleicher & Schuell
Company (Whatman 589/1 black ribbon and Whatman 589/3 black ribbon) and the sediment
quantity is determined gravimetrically. The calculated sediment amounts are related to the
water quantity in the sample to get a sediment concentration in g l -1 .
Data evaluation:
The experiments are characterised by means of the following indicators, where the water
flowing out of the rill system is considered as runoff:
intensity factor: the relationship between the maximum runoff value and the inflow
intensity, I = RI / II
duration factor: the relationship between the runoff duration and the inflow duration,
DF = RD / ID
detention: the difference between the runoff start and the inflow finish, D = RS - IF
time factor: the relationship between these two values, T = RS / IF
runoff rate: relationship between runoff quantity and inflow quantity. This factor
neglects the influence of the flow length, but it is an indicator to the infiltration
characteristics within the rill, R = RQ / IQ
r-l-factor (runoff-length-factor): the relationship between the runoff- and the inflow
quantity, depending on the flow length: r-l-factor = (runoff quantity / inflow quantity )
* length [m], RL = (RQ / IQ ) * L
For characterising the rainfall simulations, we used the overall runoff coefficient. With this,
the size of the contributing area is determined, which is needed to produce a runoff of 9 l min -
1 at the starting point of each rill with a rainfall intensity of 40 mm h -1 . With a given
catchment area size and a known runoff coefficient of the rainfall simulations, the RR (Rill
runoff caused by a rainfall intensity of 40 mm h -1 in the catchment [l s -1 ] ) can be calculated,
at least the dimension.
The runoff of a river catchment can not easily be compared to a runoff in a rill. In the Arnás
catchment, runoff and sediment concentration values were measured (SEEGER et al. 2005).
We can calculate the dimension of the theoretical runoff, a runoff quantity that the Arnás river
80