shown in Eq. (3.9). The time of concentration is calculated by Giandotti’s formula,
as shown in Eq. (3.10) Giandotti (1934). The calculated time of concentration and
lag time for the basin are shown in Table 3.7.
Fig. 3.8 Slope map
Table 3.7 Time of concentration and lag time for basin
Subbasin
Tc
Tlag ¼ 0.6*tc
Subbasin
Tc
Tlag ¼ 0.6*tc
W280
1.19
0.71
W410
1.59
0.95
W300
0.92
0.55
W460
1.22
0.73
W310
0.12
0.07
W430
2.06
1.23
W300
4.28
2.57
W430
0.37
0.22
W370
0.78
0.47
W510
1.08
0.65
W370
0.65
0.39
W430
0.54
0.33
W320
3.51
2.11
W470
7.50
4.50
W330
2.82
1.69
W360
5.88
3.53
W340
2.88
1.73
W450
2.09
1.25
W400
2.99
1.79
W440
1.87
1.12
W370
3.74
2.25
W480
4.52
2.71
W390
2.41
1.45
W530
5.35
3.21
W420
2.30
1.38
W540
13.21
7.92
3 Flood Risk Assessment for a Medium Size City Using Geospatial Techniques with. . .
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