APPENDIX K: RAINFALL TABLES
   Rainfall Depth-Duration Frequency Tables for Lake County
   Rainfall is in inches
 
Duration
1 year
2 year
5 year
10 year
25 year
50 year
100 year
*Mult. factor
5 min
0.28
0.34
0.41
0.47
0.57
0.66
0.78
0.12
10 min
0.49
0.59
0.71
0.81
1.00
1.16
1.37
0.21
15 min
0.63
0.76
0.92
1.05
1.28
1.49
1.76
0.27
30 min
0.87
1.04
1.26
1.44
1.76
2.04
2.41
0.37
1 hour
1.10
1.32
1.60
1.82
2.23
2.59
3.06
0.47
2 hour
1.36
1.62
1.97
2.25
2.76
3.19
3.77
0.58
3 hour
1.50
1.79
2.18
2.48
3.04
3.52
4.16
0.64
6 hour
1.76
2.10
2.55
2.91
3.56
4.13
4.88
0.75
12 hour
2.04
2.44
2.96
3.38
4.13
4.79
5.66
0.87
18 hour
2.21
2.63
3.20
3.65
4.47
5.17
6.11
0.94
24 hour
2.35
2.80
3.40
3.88
4.75
5.50
6.50
1.00
48 hour
2.54
3.02
3.67
4.19
5.13
5.94
7.02
1.08
72 hour
2.73
3.25
3.94
4.50
5.51
6.38
7.54
1.16
120 hour
3.25
3.93
4.9l
5.70
6.93
8.04
9.96
**6 county
240 hour
4.12
4.95
6.04
6.89
8.18
9.38
11.14
**6 county
 
References: IDNR/OWR Floodplain Map Revision Manual, March 1996, Bulletin 70 1988
*Multiplication Factor - Average ratios of X-hour/24-hour rainfall for Illinois, 1989 Bulletin 70
**6 County - A multiplicative factor is not available for these storm events. Therefore, the 6-county Bulletin 70 data is used for regulatory studies.
HUFF RAINFALL DISTRIBUTIONS
The Huff quartiles represent the typical rainfall distribution for four different storm duration ranges. The First quartile applies to storms less than or equal to six hours long. Second is for storms greater than six hours and less than or equal to 12, while the third Huff quartile is for storms greater than 12 hours and less than or equal to 24 hours. Fourth quartile storms apply to storm durations greater than 24 hours.
 
HUFF QUARTILE DISTRIBUTIONS
CUMUL.
STORM PERCENT
AREA< 10 SM
AREA > 10 & AREA < 50
AREA > 50 & AREA < 400
HUFF QUARTILE
HUFF QUARTILE
HUFF QUARTILE
1st
2nd
3rd
4th
1st
2nd
3rd
4th
1st
2nd
3rd
4th
05
16
03
03
02
12
03
02
02
08
02
02
02
10
33
08
06
05
25
06
05
04
17
04
04
03
15
43
12
09
08
38
10
08
07
34
08
07
05
20
52
16
12
10
51
14
12
09
50
12
10
07
25
60
22
15
13
62
21
14
11
63
21
12
09
30
66
29
19
16
69
30
17
13
71
31
14
10
35
71
39
23
19
74
40
20
15
76
42
16
12
40
75
51
27
22
78
52
23
18
80
53
19
14
45
79
62
32
25
81
63
27
21
83
64
22
16
50
82
70
38
28
84
72
33
24
86
73
29
19
55
84
76
45
32
86
78
42
27
88
80
39
21
60
86
81
57
35
88
83
55
30
90
86
54
25
65
88
85
70
39
90
87
69
34
92
89
68
29
70
90
88
79
45
92
90
79
40
93
92
79
35
75
92
91
85
51
94
92
86
47
95
94
87
43
80
94
93
89
59
95
94
91
57
96
96
92
54
85
96
95
92
72
96
96
94
74
97
97
95
75
90
97
97
95
84
97
97
96
88
98
98
97
92
95
98
98
97
92
98
98
98
95
99
99
99
97
 
References: Floyd A. Huff and James R. Angel, 1989 ‘Frequency Distributions and Hydroclimatic Characteristics of Heavy Rainstorms in Illinois’, Illinois State Water Survey, Bulletin 70.
(Ord., Appendix K, passed 10-13-2009)