This command calculates peak flow using the tabular hydrograph method from the TR-55 program. The program is run through the dialog shown below. The Curve Numbers & Runoff and Time of Concentration routines can be used to calculate the subarea input values. When all the inputs are entered, click on the Calculate button. The input values can be saved to a file by clicking the Save button. Then the Load button can be used later to recall these entered values. The peak flow report lists the flow for each subarea at different time. The peak flow value is listed at the end of the report. This value can then be used for Detention Pond Sizing or Channel Design.
See the TR-55 manual for more details on this routine. One difference between Carlson and the TR-55 example is that Carlson interpolates the flow for the subarea Ia/P between the two nearest table Ia/P values whereas TR-55 uses the one closest Ia/P table entry. Consider a subarea with an Ia/P value of 0.14 and table entries of 100 cfs at 0.1 Ia/P and 75 cfs at 0.3 Ia/P. TR-55 would use 100 cfs from the nearest 0.1 Ia./P entry. Carlson would interpolate between 100 and 75 cfs resulting in 95 cfs.
Peak Flow Tabular Hydrograph Method
Subarea Drainage Time of Travel Downstream Travel Rainfall Curve Runoff
name area concen- time for subarea time number
(sq. mi.) tration subarea names summation
1 0.3000 1.50 0.00 3,5,7 2.50 6.00 65 2.35
2 0.2000 1.25 0.00 3,5,7 2.50 6.00 70 2.81
3 0.1000 0.50 0.50 5,7 2.00 6.00 75 3.28
4 0.2500 0.75 0.00 5,7 2.00 6.00 70 2.81
5 0.2000 1.50 1.25 7 0.75 6.00 75 3.28
6 0.4000 1.50 0.00 7 0.75 6.00 70 2.81
7 0.2000 1.25 0.75 0.00 6.00 75 3.28
Time 11.0 11.3 11.6 11.9 12.0 12.1 12.2 12.3
Subarea Discharge (cfs)
1 0 0 1 1 1 1 1 2
2 0 1 1 1 2 2 2 2
3 1 1 2 2 2 2 3 3
4 2 2 3 3 4 4 4 5
5 3 4 5 7 7 8 9 10
6 4 6 7 10 11 11 12 14
7 6 8 11 15 18 24 34 51
Total 17 23 30 40 45 53 65 87
Time 12.4 12.4 12.6 12.7 12.8 13.0 13.2 13.4
Subarea Discharge (cfs)
1 2 2 2 2 3 3 3 4
2 2 2 3 3 3 4 4 5
3 3 3 4 4 5 6 7 11
4 5 6 6 7 7 9 11 16
5 11 13 16 20 26 48 80 115
6 16 19 23 29 39 74 127 186
7 75 104 137 165 184 202 173 139
Total 114 149 189 230 267 345 406 475
Time 13.6 13.8 14.0 14.3 14.6 15.0 15.5 16.0
Subarea Discharge (cfs)
1 5 6 8 17 38 85 134 130
2 6 8 13 27 56 101 122 92
3 20 39 65 96 91 59 29 17
4 28 54 96 161 185 147 82 48
5 143 156 152 126 97 67 44 32
6 234 257 253 213 166 116 78 57
7 107 85 69 52 41 31 25 21
Total 544 606 654 692 674 608 516 397
Time 16.5 17.0 17.5 18.0 19.0 20.0 22.0 26.0
Subarea Discharge (cfs)
1 94 64 46 35 25 19 15 10
2 59 39 28 22 16 13 10 7
3 13 11 10 9 7 6 5 3
4 33 27 23 21 17 15 11 8
5 25 21 18 16 13 12 9 3
6 46 39 33 30 25 22 17 6
7 18 16 15 13 12 11 8 1
Total 289 217 173 146 115 99 74 39
Peak Discharge: 692 cfs
Pulldown Menu Location: Watershed
Keyboard Command: peakflow
Prerequisite: None