2.4 Experimental Methods and Materials
21
applied to the initial ground cover of the Model Da without check dams. The landform
was then returned to the initial state. Then, 10 rainfall events, with the same properties as above mentioned were applied, while 12 check dams were orderly constructed
(Table 2.3). (3) Two groups of experiments were performed for the Model Db. First,
6 rainfall events, generated by the SX2004 Sprayer-styled Rainfall Simulator with
the intensities of about 2.45 mm/min and a duration of 10 min, were applied to the
initial ground cover of the Model Db which was made of mixed soil and cultivated
slopes before check dams were constructed. The landform was then returned to the
initial state and 10 rainfall events, which had the same properties of the experiments
above mentioned were applied, while 12 check dams were orderly constructed, as
shown in Table 2.4.
To counteract the error of soil loss caused by the difference in the rainfall intensities. The rainfall intensity was strongly correlated with the soil loss in the experiments. Thus, a group of experiments was conducted on the Model Da to assess the
relationship between the rainfall intensity and soil loss, and to identify a method
for counteracting soil loss error caused by differences in rainfall intensities. In these
experiments, no dam was built on the initial landform. The duration of each rainfall
event was 10 min. However, the rainfall intensity in each rainfall event was different.
The landform was returned to its initial state and pre-wetted before each rainfall
event.
2.5 Results and Discussion
2.5.1 Counteraction of the Soil Loss Error Caused
by Different Rainfall Intensity
Seven rainfall simulation experiments were conducted on the Model Da using the
same initial landform and same initial water content. Table 2.5 presents the experimental results. For experiments under the following conditions of (1) with the same
initial degree of saturation of bare land, (2) no large obstacle that blocks water, e.g.,
no check dam or pond, and (3) the same duration for each rainfall event, soil loss,
S D , was expressed as a power function of rainfall intensity, I D :
S D = 0.993I
1.98
D , r
2
= 0.94
(2.5)
Similar experimental results were obtained by several experiments conducted on
the Model Db without any dams. Accordingly, soil loss error caused by different rainfall intensities between the expected value and observed value could be counteracted
as follows:
S
∗
D = S D × ( ¯
I D /I D )
1.98
(2.6)
21
applied to the initial ground cover of the Model Da without check dams. The landform
was then returned to the initial state. Then, 10 rainfall events, with the same properties as above mentioned were applied, while 12 check dams were orderly constructed
(Table 2.3). (3) Two groups of experiments were performed for the Model Db. First,
6 rainfall events, generated by the SX2004 Sprayer-styled Rainfall Simulator with
the intensities of about 2.45 mm/min and a duration of 10 min, were applied to the
initial ground cover of the Model Db which was made of mixed soil and cultivated
slopes before check dams were constructed. The landform was then returned to the
initial state and 10 rainfall events, which had the same properties of the experiments
above mentioned were applied, while 12 check dams were orderly constructed, as
shown in Table 2.4.
To counteract the error of soil loss caused by the difference in the rainfall intensities. The rainfall intensity was strongly correlated with the soil loss in the experiments. Thus, a group of experiments was conducted on the Model Da to assess the
relationship between the rainfall intensity and soil loss, and to identify a method
for counteracting soil loss error caused by differences in rainfall intensities. In these
experiments, no dam was built on the initial landform. The duration of each rainfall
event was 10 min. However, the rainfall intensity in each rainfall event was different.
The landform was returned to its initial state and pre-wetted before each rainfall
event.
2.5 Results and Discussion
2.5.1 Counteraction of the Soil Loss Error Caused
by Different Rainfall Intensity
Seven rainfall simulation experiments were conducted on the Model Da using the
same initial landform and same initial water content. Table 2.5 presents the experimental results. For experiments under the following conditions of (1) with the same
initial degree of saturation of bare land, (2) no large obstacle that blocks water, e.g.,
no check dam or pond, and (3) the same duration for each rainfall event, soil loss,
S D , was expressed as a power function of rainfall intensity, I D :
S D = 0.993I
1.98
D , r
2
= 0.94
(2.5)
Similar experimental results were obtained by several experiments conducted on
the Model Db without any dams. Accordingly, soil loss error caused by different rainfall intensities between the expected value and observed value could be counteracted
as follows:
S
∗
D = S D × ( ¯
I D /I D )
1.98
(2.6)