HomeMy WebLinkAboutWPO201400059 Calculations 2014-06-12 'fir 'Nino
U.S.Department of Agriculture FL-ENG-21A
Natural Resources Conservation Service 06/04
TR 55 Worksheet 2:Runoff Curve Number and Runoff
Project: Briarwood Commercial Development Designed By: FGM,PE Date: 6/9/2014
Location: Briarwood Drive&Rte.29 Checked By: FGM,PE Date: 6/9/2014
Check One: Present X Developed X
1.Runoff curve Number(CN)
a Soil name and Cover description
Drainage CN(weighted)=
Area hydrologic group (Cover type,treatment,and hydrologic condition; Area Product of Calculated
percent impervious;unconnected/connected CN total product/
Description (Appendix A) p p ec (Acres) CN x Area total area '5'Value
impervious area ratio)
DA#1C Approved Bypassed Imp.Areas-Rte.29&Briarwood Dr. 98 0.28 27.4
(Present)
B Woods in Good Condition(approx.50%) 55 1.28 70.1 62.0 6.14
Lawns in Good Condition (approx.50%) 61 1.28 77.8
DA#1C Impervious Areas 98 0.81 79.9
(Routed) B Woods in Good Condition(approx.50%) 55 0.00 0.0 95.3 0.50
Lawns in Good Condition (approx.50%) 61 0.07 4.0
DA#1C Approved Bypassed Imp.Areas-Rte.29&Briarwood Dr. 98 0.40 39.2
(Unrouted) B Woods in Good Condition 55 0.00 0.0 77.1 2.97
Lawns in Good Condition 61 0.52 31.7
2.Runoff
2-Year Storm 10-Year Storm Drainage Area Description
Frequency-years 2 10 n/a
Rainfall,P(24 hour)-inches 3.7 5.6 n/a
Runoff,Q-inches
Runoff,Q-inches
Runoff,Q-inches 0.71 1.82 DA#1C(Present)
Runoff,Q-inches
Runoff,Q-inches 3.16 5.04 DA#1C(Routed)
Runoff,Q-inches 1.59 3.14 DA#1C(Unrouted)
Runoff,Q-inches
Runoff,Q-inches
U.S.Department of Agriculture FL-ENG-21A
Natural Resources Conservation Service 06/04
TR 55 Worksheet 3:Time of Concentration(T)or Travel Time(Ti)
Project: Briarwood Commercial Development Designed By: FGM,PE Date: 6/9/2014
Location: Briarwood Drive&Rte.29 Checked By:FGM,PE Date: 6/9/2014
Check One: Present X Developed X
Check One: T, X T, Through subarea n/a
DA#1C DA#1C DA#1C
Segment ID: (Present) (Routed) (Unrouted)
Sheet Flow:(Applicable to T,only)
1 Surface description(Table 3-1) Dense Grass Dense Grass
2 Manning's roughness coeff.,n(Table 3-1 0.24 0.24
3 Flow length,L(total L<100)(ft) 100 100
4 Two-year 24-hour rainfall,P5(in.) 3.7 3.7
5 Land slope,s(ft/ft) 0.11 0.19
6 Compute T,=[0.007(n*L)°8]/1,2"S I 0.11 I 1 I 0.09 I
Shallow Concentrated Flow:
7 Surface description(paved or unpaved) Unpaved Unpaved
8 Flow Length,L(ft) 250 300
9 Watercourse slope,s(ft/ft) 0.168 0.04
10 Average velocity,V(Figure 3-1)(ft/s) 6.8 3.2
11 T=L/3600V I I 0.01 I I I 0.03 I
Channel Flow:
12 Cross sectional flow area,a(f2)
13 Wetted perimeter,P,,,(ft)
14 Hydraulic radius,r=a/PP,(ft)
15 Channel Slope,s(ft/ft)
16 Manning's Roughness Coeff,n
17 V=[1.49r213s°s]/n
18 Flow length,L(ft)
19 T,=L/3600*V I I I I I
20 Watershed or subarea T,or T,
(Add T,in steps 6,11 and 19) I I 0.12 I ' 0.10 I 0.12 I
NOTE:Minimum SCS time of concentration is 0.10 hours.
*like gale
U.S.Department of Agriculture FL-ENG-21C
Natural Resources Conservation Service 06/04
TR 55 Worksheet4:Graphical Peak Discharge Method
Project: Briarwood Commercial Development Designed By: FGM,PE Date: 6/9/2014
Location: Briarwood Drive&Rte.29 Checked By: FGM,PE Date: 6/9/2014
Check One: Present X Developed X
Drainage Drainage Area Drainage Drainage Area Drainage Area Drainage Area Drainage Drainage Area
I.Data Area Description Area Description Description Description Area Description
DA#1C DA#1C DA#1C
(Present) (Routed) (Unrouted)
Drainage Area(Am)in miles a= 0.0044 0.0014 0.0014
Runoff curve number CN= 62.0 95.3 77.1
Time of concentration(Tc)= 0.12 0.10 0.12
Rainfall distribution type= II II II
Pond and swamp areas spread 0 0 0
throughout the watershed=
2.Frequency-years 2 10 2 10 2 10
3.Rainfall,P(24 hour)-inches 3.7 5.6 3.7 5.6 3.7 5.6
4.Initial Abstraction,la-inches 1.23 1.23 0.099 0.099 0.594 0.594
5.Compute la/P 0.33 0.22 0.03 0.02 0.16 0.11
6.Unit peak discharge,Qu-csm/in 850 925 975 1000 925 950
7.Runoff,Q from Worksheet 2-inches 0.71 1.82 3.16 5.04 1.59 3.14
8.Pond and Swamp adjustment factor,Fp 1 1 1 1 1 1
9.Peak Discharge,Qp-cfs Routed Through
where Qp=Qu Am Q Fp 2.67 7.44 SWM Facility 2.11 4.29
NOTE:Qu of 1000 csm/in is the most conservative value for the type II rainfall distribution
Watershed Summary
2 year Storm Event
DA#1C(Present) 2.67 cfs > DA#1C(Routed) 0.54 cfs
DA#1C(Unrouted) 2.11 cfs
Total= 2.67 cfs Total= 2.65 cfs
10 year Storm Event
DA#1C(Present) 7.44 cfs > DA#1C(Routed) 2.85 cfs
DA#1C(Unrouted) 4.29 cfs
Total= 7.44 cfs Total= 7.14 cfs