ChannelFlow: IDF File or Constant

The IDF Curve File can either be a file name, or a number. If a number is given, it will be applied as the intensity to all "Qcia" lines in the table, overriding any values input on each line. If a file name is given, it will read the file, which must contain an IDF curve, and use the time of concentration to generate intensity values in "Qcia" lines. The IDF curves for Ablemarle County Virginia are coded into the program. Use "a2", "a10", or "a100" for the 2, 10 and 100 year storm IDF curves. If you would like the IDF curves for your area coded into the program, please contact me.

The general form of the IDF curve file must be:

...Curve:
duration intensity
0  5.0
6.2 5.63
7   7.2
8.0   10

...

The key string "Curve:" starts the reading of input value pairs, after a skipped line assumed to be the table header.  Value pairs are separated by spaces, one pair to a line.  A blank line at the end will terminate the reading of input pairs.  Anything else in the file before or after this key word and sequence is ignored. You may need to specify the complete path and file name, depending on your system setup. A sample IDF curve file is shown below.

Sample IDF curve file

IDF Curve Albemarle County 2yr 

Curve:
duration   intensity (in/hr)
0 5.5
5 5.5
6 5.15
7 4.85
8 4.6
9   4.33
10   4.16
11   4.00
12   3.85
13   3.72
14   3.59
15   3.47
16   3.36
17   3.26
18   3.16
19   3.07
20   2.99
21   2.90
22   2.83
23   2.75
24   2.68
25   2.62
26   2.55
27   2.49
28   2.44
29   2.38
30   2.33
31   2.28
32   2.23
33   2.19
34   2.14
35   2.10
36   2.06
37   2.02
38   1.98
39   1.94
40   1.91
41   1.88
42   1.84
43   1.81
44   1.78
45   1.75
46   1.72
47   1.70
48   1.67
49   1.64
50   1.62
51   1.59
52   1.57
53   1.55
54   1.53
55   1.50
56   1.48
57   1.46
58   1.44
59   1.42
60   1.40
1440 1.40

from Virginia Stormwater Management Handbook Appendix 4D, and formula of p.5-19

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