Geoscience Reference
In-Depth Information
Runoff for Fuzzy SCSCN model
(mm)
Runoff for
Boolean SCSCN
model
(mm)
Recorded
runoff
(mm)
rain
(mm)
Event
Linear
membership
function
Bell-shaped
membership
function
rain 1
5.5
2.1
0
0
0
rain 2
14
2.4
0
0
0
rain 3
21.2
3.4
0
0
0
rain 4
27.4
4.5
0.2
0
0
rain 5
32.8
5
0
1
1
rain 6
35.5
5
1.0
1
1
rain 7
45
7
2
3
3
rain 8
46
7
2
3
3
rain 9
56.5
12.6
5
6
6
rain 10
71.6
14
10
12.3
12.3
rain 11
87.0
19
16.6
18.4
18.6
rain 12
122.6
40
31
37
37
rain 13
134
49
43.2
50
50
rain 14
140.2
56
53
57
57
rain 15
150
59
54
58
58
rain 16
162
62
59
61.5
61.7
Table 4. Simulated runoff with the Boolean SCSCN and with the Fuzzy SCSCN using sixteen
rain events
Runoff simulations with the Fuzzy SCSCN model were accomplished using recorded
precipitation data in the watershed (Table 4). Runoff modeling was also carried out using
soil and vegetation cover data in Boolean format. The notion here was to compare the
results derived from conventional SCSCN model and the Fuzzy SCSCN model, as presented
in Table 4.
Figure 8 portrays two maps with the spatial distribution of the CNs calculated for the Fuzzy
SCSCN model and for the boolean SCSCN model. These CN maps represent the capacity of
the land to produce surface runoff from a rain event. It is clear that there is a greater variety
of values of the parameter CN when it is calculated by the Fuzzy SCS model. Using the
boolean SCSCN model it was possible to achieve only 8 CNs, whereas a larger range of CNs
was yielded with the fuzzy SCSCN.
The simulated runoff values derived from the Fuzzy SCSCN model were closer to measured
runoff values in the watershed than the simulated runoff values yielded from the Boolean
SCSCN model (Table 4). The better performance reached by the fuzzy model signifies that it
can conveniently express natural phenomena, including zones of imprecision and/or
uncertainties like transition zones among soil types and vegetation cover. Table 4 shows that
the runoff data calculated by the models (from rain 1 to rain 9) is not in agreement with the
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