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

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Experimentelle Rinnenerosionsforschung vs. Modellkonzepte – Quantifizierung der hydraulischen und erosiven Wirksamkeit von Rinnen All three erosion parameters showed higher values in the experiment with goat trampling, but the difference is most obvious in the dry run. In the second (wet) run, the values were equal or at least similar to the values of the experiments without trampling. Transport and detachment rate were about 5 times higher in the dry run with goat trampling as in the runs without trampling. Sediment concentration in the dry run with trampling was about 2.5 higher compared to the experiment without trampling (see figure 8). Interpretation: The rill experiment clearly shows the short-term influence of goat trampling. Livestock’s hooves’ impact prepares the soil surface and a large quantity of loose material is made ready for transport (see experiment 4). Crucially, this material is removed very fast; the second run with trampling still shows nearly the same values as the runs without preceding trampling. The sediment concentrations at the waterfront were clearly higher in the experiment with trampling, whereas the other samples show similar concentrations. Accordingly, trampling provides a large quantity of loose material but its impact on mobilization is only detectable for a short time. 3.6 Statistical analysis In table 1, the statistical values of the experiments 1, 2 and 4 are summarized. In experiment 1 and 2, the first run was not used in the calculations to avoid mistakes caused by the installation of the troughs. The difference between mean and standard deviation increases with slope, meaning high quantities as well as low quantities of substrate can be translocated. The quantity of the mean increases with slope but the values become less stable. This is also detectable in figure 8. Regarding the values for the movement parallel to contour lines, the differences between mean and standard deviation for trough 1 and 2 in each version are very similar, they are in all three cases between 52 and 58 %. But in all three cases, the first trough shows clearly higher differences than the second trough. Because of the low n-values, we do not want to over-interpret the values and conclude that the high values for trough 1 are caused by the jumping-in and -out of the animals at the beginning of the test plot. Once they are inside the fenced course, the movements are smoother. Figure 9 shows that again, the fast running speed can cause very high values as well as low values, the mean values are clearly higher than under slow movement but the values are less stable. The high difference between 245
Experimentelle Rinnenerosionsforschung vs. Modellkonzepte – Quantifizierung der hydraulischen und erosiven Wirksamkeit von Rinnen mean and standard deviation in the loosening experiment can be explained by the slow increase at the beginning due to breaking the crust. Table 1: Statistical values of the different experiments. St.Dev. = standard deviation, T1 = Gerlach Trough A, T2 = Gerlach Trough B Mean [g] Median St.Dev. IMean-St.Dev.I % from mean [g] [g] Slope 8.5° 93.1 66.1 104.9 11.8 12.7 Slope 12° 250.5 231.9 132.3 118.2 47.2 Slope 20° 1047.0 1032.3 299.1 747.9 71.4 Trail A slow T1 92.3 76.5 34.3 58.0 62.8 Trail A slow T2 62.6 67.0 32.9 29.7 47.4 Trail A fast T1 374.2 402.0 120.1 254.1 67.9 Trail A fast T2 328.8 233.0 169.0 159.8 48.6 Trail B slow T1 105.1 116.0 25.5 79.6 75.7 Trail B slow T2 39.6 31.1 28.2 11.4 28.8 Loosening 1322.2 1431.5 394.8 927.4 70.1 Figure 9: Boxplots of the different experimental setups. T1 = Gerlach Trough A, T2 = Gerlach Trough B 246
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Stefan Wirtz Vom Fachbereich VI (Ge
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Danksagung Danksagung Die vorliegen
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Experimentelle Rinnenerosionsforsch
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Stefan Wirtz Vom Fachbereich VI (Geographie/Geowissenschaften ...

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