56
4 An Innovative Measurement Instrument …
workload is relatively minor, and the method is faster and more precise. Hence, the
volume of “pure” gravity erosion could be also calculated by clearly differentiating
gravity erosion from hydraulic erosion.
4.4.3 Case Study for the Total Amount of Erosion
Figure 4.6a, b show the screenshots in the experiment group L60-1.5-80d, of which
the initial slope height was 1.5 m and the initial gradient was 80°, at the beginning
of the 2nd rainfall and soon after a 60 min rainfall, respectively. Figures 4.6c and d
are the three-dimensional models formed according to the screenshots. According to
the three-dimensional vectors as mentioned above, the total amount of soil erosion
during the rainfall was figured out, having the number of 239.16 × 10
3 cm
3 .
For experiment group L60-1.5-80d, the calculated results of gravity erosions are
illustrated in Table 4.3. For instance, in the 3rd rainfall event, gravity erosion with
volumes more than 100 cm
3 occurred 2 times, and the total amount reached 6.21 × 10
3
cm
3 , all of which were completed in a very short time. Simultaneously, the amount of
hydraulic erosion was 4.64 × 10
3 cm
3 , which lasted for the whole period of rainfall
simulation. In the 2nd, 3rd and 4th rainfall events, the amount of gravity erosion
accounted for up to 91.89, 57.21 and 66.47% of the total erosions, respectively. As
a result, gravity erosion is more dangerous than hydraulic erosion on the steep loess
slope.
4.4.4 Limitations and Future Developments
Just like any other structured-light 3D surface measuring techniques, the topography
meter casts straight lights on the slope and has difficulty in handling the cavities
Table 4.3 Total amount of soil loss during a rainfall: a sample
Experimental
group
Rainfall
event
Events of
gravity
erosion
Soil loss during rainfall (10 3 cm 3 )
G1
T (%)
Total
erosion
(T )
Gravity
erosion
(G 1 )
Hydraulic
erosion
(H)
L60-1.5-80d
120924-1
3
13.09
0.85
12.23
6.50
120924-2
21
260.27
239.16
21.11
91.89
120925-3
2
10.85
6.21
4.64
57.21
120925-4
7
538.04
357.63
180.41
66.47
120926-5
0
22.36
0.00
22.36
0.00
120926-6
8
240.61
105.75
134.86
43.95
The data were obtained from the second rainfall of the L60-1.5-80d experimental group
4 An Innovative Measurement Instrument …
workload is relatively minor, and the method is faster and more precise. Hence, the
volume of “pure” gravity erosion could be also calculated by clearly differentiating
gravity erosion from hydraulic erosion.
4.4.3 Case Study for the Total Amount of Erosion
Figure 4.6a, b show the screenshots in the experiment group L60-1.5-80d, of which
the initial slope height was 1.5 m and the initial gradient was 80°, at the beginning
of the 2nd rainfall and soon after a 60 min rainfall, respectively. Figures 4.6c and d
are the three-dimensional models formed according to the screenshots. According to
the three-dimensional vectors as mentioned above, the total amount of soil erosion
during the rainfall was figured out, having the number of 239.16 × 10
3 cm
3 .
For experiment group L60-1.5-80d, the calculated results of gravity erosions are
illustrated in Table 4.3. For instance, in the 3rd rainfall event, gravity erosion with
volumes more than 100 cm
3 occurred 2 times, and the total amount reached 6.21 × 10
3
cm
3 , all of which were completed in a very short time. Simultaneously, the amount of
hydraulic erosion was 4.64 × 10
3 cm
3 , which lasted for the whole period of rainfall
simulation. In the 2nd, 3rd and 4th rainfall events, the amount of gravity erosion
accounted for up to 91.89, 57.21 and 66.47% of the total erosions, respectively. As
a result, gravity erosion is more dangerous than hydraulic erosion on the steep loess
slope.
4.4.4 Limitations and Future Developments
Just like any other structured-light 3D surface measuring techniques, the topography
meter casts straight lights on the slope and has difficulty in handling the cavities
Table 4.3 Total amount of soil loss during a rainfall: a sample
Experimental
group
Rainfall
event
Events of
gravity
erosion
Soil loss during rainfall (10 3 cm 3 )
G1
T (%)
Total
erosion
(T )
Gravity
erosion
(G 1 )
Hydraulic
erosion
(H)
L60-1.5-80d
120924-1
3
13.09
0.85
12.23
6.50
120924-2
21
260.27
239.16
21.11
91.89
120925-3
2
10.85
6.21
4.64
57.21
120925-4
7
538.04
357.63
180.41
66.47
120926-5
0
22.36
0.00
22.36
0.00
120926-6
8
240.61
105.75
134.86
43.95
The data were obtained from the second rainfall of the L60-1.5-80d experimental group