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

Experimentelle Rinnenerosionsforschung vs. Modellkonzepte – Quantifizierung der hydraulischen und erosiven Wirksamkeit von Rinnen
qS
w
TC =
31 Q
32
33
34
35
TC = transport capacity in clear water [g L -1 ], ρ S = density of solid material [kg m -3 ], w
= flow width [m], Q = runoff [m³ s -1 ]
Yalin (1993), Bagnold (1980)
ρ
f
TC =
( 1
CP
1E6
CP
)
1E6
TC = transport capacity in clear water [g L -1 ], ρ f = fluid density [kg m -3 ], C P =
concentration [ppm]
Yang (1973)
1.5
TC = k t
τ
f
TC = transport capacity [kg s -1 ], k t = transport coefficient [m 0.5 s² kg -0.5 ], τ f = hydraulic
shear acting on the soil [Pa]
Foster et al. (1995)
11.2 (τ τ
QB
=
3
(τ )
c
c
)
4.5
Q B = transport rate per unit of width [kg 1.5 m -1.5 s -3 ], τ c = threshold value of τ required to
initiate particle motion, τ = shear stress [Pa]
Parker (1979)
D
C
= K
r
(τ
τ
cr
)
D C = detachment capacity [kg m -2 s -1 ], K r = rill erodibility factor [s m -1 ], τ = shear stress
[Pa], τ cr = critical shear stress [Pa]
Foster et al. (1995)
Constant soil parameters?
Another important fact which cannot be handled by the process based models is the
heterogeneity in critical shear stress. In this study, we performed our experiments on one field
with uniform treatment, hence the soil parameters are as constant as possible. As a
consequence, we assumed the critical shear stress to be constant in our experiments. In a
typical model, the critical shear stress for cropland with a sand content > 30% (at our test side:
about 80%, mainly middle, fine and very fine sand) is calculated using the clay and the very
fine sand content and these values are constant. This assumes a constant critical shear stress
but in reality, this homogeneity is not found. The critical shear stress can also change between
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