§ 17.60.180 APPENDIX 4: RAINFALL DEPTH-DURATION FREQUENCY TABLES FOR MCHENRY COUNTY.

   Angel, J. R., M. Markus, K. A. Wang, B. M. Kerschner, S. Singh. 2020. Precipitation Frequency Study for Illinois. Illinois State Water Survey Bulletin 75, Champaign, IL.

 

Huff Quartiles for Time Distribution of Heavy Rainfall
Duration ≤ 6 hours	1st Quartile
6 hours < Duration ≤ 12 hours	2nd Quartile
12 hours < Duration ≤ 24 hours	3rd Quartile
Duration > 24 hours	4th Quartile

 

Portion of the Storm	Drainage Area under 10 Square Miles				Drainage Area 10 to 50 Square Miles				Drainage Area 50 to 400 Square Miles
	1st	2nd	3rd	4th	1st	2nd	3rd	4th	1st	2nd	3rd	4th
0/24	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
1/24	8.36	2.29	2.05	2.31	6.41	1.48	1.33	1.48	4.59	0.88	0.72	0.90
2/24	17.73	4.82	4.31	4.79	15.69	3.57	3.02	3.34	13.49	2.38	1.85	2.29
3/24	28.11	7.78	6.67	7.12	27.45	6.39	5.13	5.72	25.94	4.93	3.47	4.36
4/24	38.33	11.33	9.12	9.78	38.91	10.02	7.53	8.56	39.17	8.52	5.57	7.10
5/24	47.45	15.79	11.71	12.53	49.34	14.71	10.01	11.69	51.04	13.19	8.28	9.93
6/24	55.50	21.39	14.36	15.23	58.55	20.89	12.65	14.19	60.79	19.59	10.96	12.84
7/24	62.25	28.41	16.91	17.91	65.88	28.91	15.24	17.19	69.26	27.46	13.79	15.46
8/24	67.22	36.44	19.64	20.33	71.10	37.55	18.17	19.69	74.80	37.17	16.35	17.83
9/24	70.82	45.29	22.78	22.83	74.92	46.86	21.46	22.27	78.74	47.77	19.66	20.12
10/24	74.17	54.35	26.33	25.41	78.30	56.25	25.36	24.81	82.20	58.18	23.46	23.12
11/24	76.97	62.38	30.93	28.35	81.16	64.84	29.90	27.46	85.13	67.64	28.07	25.76
12/24	79.81	69.76	36.35	31.25	83.75	72.90	35.60	30.33	87.38	75.86	34.06	28.26
13/24	82.55	75.48	43.92	33.90	86.20	79.07	43.42	32.42	89.58	82.04	42.30	30.99
14/24	85.18	80.38	52.11	36.33	88.64	83.97	52.18	34.28	91.45	86.92	52.02	33.68
15/24	87.40	84.70	61.02	38.61	90.81	87.58	61.88	36.89	93.35	90.33	62.76	36.12
16/24	89.47	87.81	69.89	41.24	92.58	90.67	71.81	39.73	94.80	93.09	72.80	39.07
17/24	91.17	90.22	78.19	45.08	93.99	92.76	80.43	43.85	95.99	94.82	82.2 7	42.9 3
18/24	92.70	92.17	84.92	51.29	95.19	94.59	87.25	49.87	96.94	96.25	89.1 9	48.9 8
19/24	94.03	93.81	89.74	59.31	96.35	95.97	92.01	58.9 3	97.7 0	97.3 4	93.6 0	59.2 2
20/24	95.36	95.29	93.11	69.19	97.27	97.10	95.04	69.8 5	98.3 5	98.2 1	96.3 3	71.6 6
21/24	96.56	96.57	95.34	80.05	98.03	97.9 9	96.90	82.3 6	98.8 6	98.8 3	97.9 7	85.1 8
22/24	97.74	97.74	97.06	89.71	98.74	98.72	98.22	92.5 9	99.2 8	99.3 0	98.9 8	94.6 4
23/24	98.8 5	98.84	98.56	96.04	99.37	99.39	99.21	97.9 6	99.6 6	99.6 7	99.5 8	98.7 7
24/24	100. 00	100.0 0	100. 00	100.0 0	100.0 0	100. 00	100.0 0	100. 00	100. 00	100. 00	100. 00	100. 00

 

(Ord. O-2020-09-15, passed 9-15-2020; Ord. O-202009-10-030, passed 9-15-2020)