SW6240606_Design Calculations (Swales)_20240830 (8)

4D Site Solutions, Inc.
DITCH CALCULATIONS
NOTE:sheet only set up to handle Tc from 5 min to 30 min
A. Flow velocity<2.0 fps when discharging to wetlands B. Flow velocity<4.5 fps all other cases** C. Channel slope<5.0%for curb outlet swales
2050-Village at Rockfish Phase V
Rainfall Intensity
Storm Event
5-min 10-min 15-min 30-min Runoff Coeff.
10-yr 7.91 6.33 5.34 3.87 Impervious 0.95
25-yr 8.94 7.12 6.01 4.46 Grassed 0.30
50-yr 9.65 7.68 6.49 4.89
100-yr 10.40 8.23 6.94 5.31
Tc
Drainage Impervious Grassed Storm Rainfall
Ditch No. C Kerby Kirpich Intensity Q(cfs)
Area(ac) Area(ac) Area(ac) Event(yr)
Total Tc Tc Used (in/hr)
L(ft) n s Toy L(ft) S 'FL',
1 0.39 0.30 0.09 0.80 n/a 600.0 0.012 5.90 5.90 5 10-yr 7.91 2.47
2 1.01 0.47 0.54 0.60 n/a 690.0 0.012 6.57 6.57 5 10-yr 7.91 4.79
3 0.46 0.21 0.25 0.60 n/a 650.0 0.012 6.27 6.27 5 10-yr 7.91 2.18
4 1.16 0.54 0.62 0.60 n/a 660.0 0.011 6.56 6.56 5 10-yr 7.91 5.51
5 0.97 0.45 0.52 0.60 n/a 465.0 0.022 3.84 3.84 5 10-yr 7.91 4.60
6 0.96 0.44 0.52 0.60 n/a 540.0 0.016 4.87 4.87 5 10-yr 7.91 4.56
7 1.96 0.75 1.21 0.55 n/a 645.0 0.024 4.78 4.78 5 10-yr 7.91 8.53
printed: 6/13/2024 1:44 PM Page 1 of 1