Geology Reference
In-Depth Information
Table 10.3
Erodibility parameters: comparison of experimental values and those generated by WEPP.
Cambisol
Argisol
Parameters
Experimental
WEPP
%
Experimental
WEPP
%
K i (kg s m 4 ) × 10 6
1.26433
3.30430
161.35 ( + )
3.06176
3.11220
1.65 ( + )
K r (kg N 1 s 1 )
0.0108
0.0145
34.26 ( + )
0.0268
0.0140
47.76 ( )
t c (N m 2 )
3.481
2.950
15.25 ( )
0.495
2.950
495.95 ( + )
K e (mm h 1 )
13.3
2.5
81.20 ( )
7.3
0.7
90.41 ( )
WEPP variation (%)
(%)
600,00
500,00
400,00
300,00
200,00
Cambisol
Argisol
100,00
0,00
Ki
Kr
tc
Ke
Fig. 10.4 Percentage variation
between values obtained by
experiment and those generated
by WEPP for K i , K r , t c and K e .
-100,00
-200,00
Parameters
Inter-rill erodibility was obtained from the maxi-
mum detachment rate and from the equation of
Foster (1982). The following values were obtained:
3.062 × 10 6 and 1.264 × 10 6 kg s m −4 , respectively,
for the Argisol and Cambisol. Using the modified
equation of Kinnell (1993), the respective inter-
rill erodibilities were: 3.786 × 10 6 and 1.926 × 10 6
kg s m −4 .
Due to the soil characteristics, the duration of
runs was different; for the Argisol it was 360 min-
utes and for the Cambisol it was 540 minutes.
The effective hydraulic conductivity was consid-
ered as the stable infiltration rate, which was
7.3 mm h −1 for the Argisol and 13.3 mm h −1 for the
Cambisol. The time taken for stabilization for
the Argisol (
Argisol, which reduced infiltration capacity and,
consequently, increased runoff.
The lowest detachment rates occurred at the
beginning of each experimental storm, but then
increased rapidly because of the low particle cohe-
sion of the topsoil. On the Argisol the detachment
rates increased to a maximum after about 45 min-
utes, before decreasing again. On the Cambisol
the detachment rates continued to increase and
did not stabilize until near the end of the storm.
The reason for this difference is that at the begin-
ning of runoff, the water does not have the capac-
ity to transport all the sediments, but as runoff
continues, this capacity increases such that trans-
portation of the detached sediment occurs, with
different particle diameters. Because the Argisol
has a higher proportion of aggregates, but also
contains loose particles, it resists detachment
90 minutes) was less than for the
Cambisol (
270 minutes). The explanation is
the concentration of clay in the Bt horizon in the
Search WWH ::




Custom Search