CHAPTER 9 STORMWATER CONTROL
Review Question Page References
(1) 255 (5) 261 (9) 264 (13) 268
(2) 255 (6) 262
(17) 277
(10) 267 (14) 269
(3) 258 (7) 263
(18) http://h2osparc.wq.ncsu.edu/
(11) 267 (15) 275
(4) 261 (8) 264 (12) 267 (16) 275
descprob/urbstorm.html#intro
(19) www.envirosources.com
Solutions to Practice Problems
1. Q = C x i x A = 0.6 x 2 in./hr x 15 ac = 18 cfs (Equation 9-1)
6. i = 5.8 in/hr (Figure 3.5)
9. Overland flow time = 8 min (Figure 9.3)
22
10. CN = 70 (Table 9.2)
11. Reach 1: Tc = 5 min, i = 7.6 in./hr, Q = 0.5 x 7.6 x 3 = 11.4 cfs ≈ 11 cfs
12 Reach 1: Tc = 5min, i =112mm/h,
12. (continued)
Reach 2: Inlet flow time + channel flow time = 5 + 1.8 ≈ 7 min > 6 min
channel flow time = (120/1.25) ÷ 60 = 1.6 min
Reach 3: Inlet flow time + channel flow time = 6 + 1.6 = 7.6 min, or
13. Tc = 20 min x 60 = 1200 s
14. FF = 2/10 = 0.2
15. Vol rain = 1.5 x 1800 s x 120 cfs = 32,400 ft3
24