HomeMy WebLinkAboutWPO201000057 Calculations 2013-10-08 AVI N ITY SUBDIVISION
CHANNEL ADEQUACY REPORT
Submitted on
SEPTEMBER 27, 2013
PREPARED BY:
COLLINS ENGINEERING
200 GARRETT STREET, SUITE K
CHARLOTTESVILLE, VA 22902
434.293.3719 PH 01:1 EgLT� ,
434.293.2813 FX �, OA
www.colIins-engineering.com 1601
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The revisions to the approved calculations are marked in yellow for the amendment
The Avinity Channel Adequacy Report & Calculations
Overview
The channel adequacy calculations attached were analyzed by dividing the watershed into
three major sections. These sections are described below; please see the attached sheet
entitled Channel Adequacy Plan-Amended for clarification.
Drainage Area, D.A. #1:
This section consists of drainage flowing to the south and consumes the majority of the
project's area. This section is further broken down into three subareas, DA#1A, l B and
1 C during the post-development state. All three subareas are routed through the proposed
stormwater management (SWM) facility and DA#1A consists of the approved Avinity
project while DA#1 B consists of a potential future development. DA#1 C is offsite and
does not propose improvements. DA#1 converges with `Southern DA' and flows to the
south where the downstream channel is analyzed.
Drainage Area, D.A. #2:
This section consists of the drainage flowing to Avon Street Extended on the northern
side of the project and outfalls into an existing culvert crossing the street. This drainage
area was broken down into two sections per Engineering's request during the original
approval, offsite drainage (D.A. 2A) and onsite drainage (D.A. 2B). Revisions to this
watershed were not made with the amendment.
Drainage Area, Southern D.A.:
This drainage area, when combined with drainage area#1, is used in the channel
adequacy calculations associated with the wet pond amendment. This drainage area is
unaltered in the post-development state and applies to cross sections #2-6.
Summary of Calculations
Post-Development D.A. #1 contains the following characteristics:
D.A. #1A= 9.11 ac.
CN= 81.6 (56.4 in the Pre-Development Scenario)
Type II distribution
P= 3.7 inches (2-year event)
P= 5.6 inches (10-year event)
Tc= 0.22 hours
Pre-Develo•ment DA#lA Location of Avinit Townhomes
r, Inc
r
' tea 4' .
•ti;'F • • •
•
..
1.
". y -r. -
,
44*
D.A. #1B=26.26 ac.
CN=55.0 (Assumes Forested Conditions)
Type II distribution
P= 3.7 inches (2-year event)
P= 5.6 inches(10-year event)
Tc=0.42 hours
D.A. #1C= 8.78 ac.
CN= 80.5 (59.5 in the Pre-Development Scenario and accounts for future development)
Type II distribution
P= 3.7 inches(2-year event)
P= 5.6 inches(10-year event)
Tc=0.17 hours (estimated future Tc)
After being routed through the SWM facility the post-development scenario generates
peak flows for the 2- and 10-year events of 9.82 cfs and 52.38 cfs, respectfully, for DA
#1 A, 1 B and 1C. The calculations showing this can be viewed in the attached documents.
(Note: Previously approved channel adequacy report had 2-and 10 year flows of 25.19
cfs and 66.57 cfs).
Post-Development D.A. #2 has a decreased drainage area in the post-development
scenario. This decreased area, as witnessed on sheets SWM 1 &2 of the originally
approved plans, does not require detention since the peak flows in the pre-development
scenario are greater than or equal to that of the post-development flows. For the post-
development flows entering the culvert and previously approved cross section#7, the
contributing drainage areas' have the following characteristics:
Offsite D.A. #2A
D.A.=6.34ac.
CN=68.9
Type II distribution
P= 3.7 inches(2-year event)
P= 5.6 inches(10-year event)
Tc=0.35 hours
Onsite D.A. #2B (Post-Development)
D.A.=0.68ac.
CN=93.1
Type II distribution
P= 3.7 inches(2-year event)
P= 5.6 inches(10-year event)
Tc=0.10 hours
The calculations resulting from the inflow data referenced above creates a post-
development peak flow of 8.97cfs and 21.32cfs for the 2- and 10-year events,
respectfully. The existing culvert was analyzed for capacity using the 10-year flow, and
was approved with the originally approved channel adequacy report.
The third and final watershed, Southern D.A., is composed of the remaining portion of
the watershed draining to the southern receiving channel. This area contains the
following characteristics:
D.A.=53.07 ac. (Previously approved area=54.94ac.)
CN=69
Type II distribution
P=3.7 inches(2-year event)
P= 5.6 inches (10-year event)
Tc= 0.42 hours
The CN value of 69 for this drainage area was selected due to the large grasslands and
pastures that make up its ground cover. It was also chosen because the overwhelming
majority of the soils within this drainage area are made up of soil type B. For example,
approximately 38%of the soils are 72C3, approximately 15%are soil type 58C, and
approximately 14% are soil type 88. The image below illustrates both the soil cover and
the soil type, and supports the assumed CN value listed above.
Southern DA of Modified
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The calculations resulting from the inflow data listed for Southern DA creates a post-
development peak flow of 44.61 cfs for the 2-year event. The calculations showing this
can be viewed in the attached documents. (Note: Previously approved channel adequacy
report had a 2-year peak flow of 46.33 cfs).
The 2-year flow for this drainage area was then combined with the 2-year flow routed
through the SWM facility for Post-Development D.A. #1 A, #1 B and#1 C. This is a worst
case scenario because it assumes both peak flows occur simultaneously, despite the fact
the time of peak flow being released from the proposed SWM facility is much later. This
is evident in the routing calculations provided. Regardless,the combined flow of 54.43
cfs (44.61 + 9.82 cfs) was then analyzed on cross sections#2-6. (Note: Previously
approved channel adequacy report had a combined 2-year peak flow of 71.52 cfs).
The cross sections analyzed are representative of their respective channels.
MS-19 Cross Section#2:
Overall Channel (Note: channel bottom is aded loam)
Mc SW. .
•
• .• -
1110,
Channel Banks Note: channel banks are aded loam)
N'
•
The channel at cross section 2, which has a 2.5 percent slope (based off a new survey),
contains the following characteristics:
Channel Bottom:
Description: (graded loam)
`n' value for channel bottom: 0.05*
Permissible Velocity: 5.0 ft/s**
Channel Banks:
Description: (graded loam)
Manning's `n' value for channel banks: 0.05*
Permissible Velocity for channel banks: 5.0 ft/s**
*Manning's `n' values are in accordance with Tables 5-16 through 5-21 of the VESCH.
Please see attached derivations.
**Permissible Velocities are in accordance with Table 5-22 of the VESCH
Maximum Computed Depth= 1.91'
Maximum Computed Velocity=4.82 ft/s (channel bottom)
Maximum Computed Velocity=4.46 ft/s (channel banks)
Complex Channnel- Cross Section No. 2
Input:
Slope 0.025
Flow(given) 54.431
line x y n
0 0.000 2.000 0.045 (first n value not used)
1 5.000 0.000 0.045
2 13.000 2.000 0.050
Output:
Depth 1.908
(y) ( 1.908)
Channel bed segment output:
line Q V A P
1 21.92 4.82 4.55 5.14
2 32.51 4.46 7.28 7.87
Mon Sep 30 15:11:18 EDT 2013
MS-19 Cross Section#3
Overall Channel ote: channel banks are ordinary firm loam)
—
*.`1 fS
Channel Bottom Note: channel bottom is : aded, loam to cobbles)
w.
t.-' r: - IP :,-,F . -:
Irly,et.. ,.,,,,,N e-_,AN-,
...
t _
1-4-1 r ,,,.
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..
tk
el
1.1
r t
Atl, . i
. -- i 'If _,1, /
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The channel at cross section 3, which has a 2.5 percent slope, contains the following
characteristics:
Channel Bottom:
Description: (graded, loam to cobbles)
`n' value for channel bottom: 0.055*
Permissible Velocity: 5.0 ft/s**
Channel Banks:
Description: (ordinary firm loam)
Manning's `n' value for channel banks: 0.045*
Permissible Velocity for channel banks: 3.5 ft/s**
*Manning's 'n'values are in accordance with Tables 5-16 through 5-21 of the VESCH.
Please see attached derivations.
**Permissible Velocities are in accordance with Table 5-22 of the VESCH
Maximum Computed Depth=2.09'
Maximum Computed Velocity=4.97 ft/s(channel bottom)
Maximum Computed Velocity=1.82 ft/s (channel banks)
Complex Channnel- Cross Section No. 3
Input:
Slope 0.025
Flow (given) 54.430
line x y n
0 0.000 3.000 0.045 (first n value not used)
1 4.000 1.500 0.055
2 8.000 0.000 0.055
3 12.000 1.500 0.055
4 13.000 3.000 0.045
Output:
Depth 2.092
(Y) ( 2.092)
Channel bed segment output:
line Q V A P
1 0.85 1.82 0.47 1.69
2 26.70 4.97 5.37 4.27
3 26.70 4.97 5.37 4.27
4 0.18 1.57 0.12 0.71
Mon Sep 30 15:15:23 EDT 2013
MS-19 Cross Section#4
Overall Channel (Vote: channel banks are ordinary firm loam)
• - •, • wowPc
Channel Bottom Note: channel bottom is aded, loam to cobbles)
4
•
� y
t
•
r v. ,
The channel at cross section 4, which has a 1.9 percent slope, contains the following
characteristics:
Channel Bottom:
Description: (graded, loam to cobbles)
`n' value for channel bottom: 0.055*
Permissible Velocity: 5.0 ft/s**
Channel Banks:
Description: (ordinary firm loam)
Manning's `n' value for channel banks: 0.035*
Permissible Velocity for channel banks: 3.5 ft/s**
*Manning's `n'values are in accordance with Tables 5-16 through 5-21 of the VESCH.
Please see attached derivations.
**Permissible Velocities are in accordance with Table 5-22 of the VESCH
Maximum Computed Depth= 1.49'
Maximum Computed Velocity=4.28 ft/s (channel bottom)
Maximum Computed Velocity=3.40 ft/s (channel banks)
Complex Channnel- Cross Section No. 4
Input:
Slope 0.019
Flow(given) 54.430
line x y n
0 0.000 2.000 0.035 (first n value not used)
1 3.000 0.500 0.035
2 8.000 0.000 0.055
3 12.000 0.500 0.055
4 15.000 2.000 0.035
Output:
Depth 1.490
(y) ( 1.490)
Channel bed segment output:
line Q V A P
1 3.33 3.40 0.98 2.21
2 26.56 4.28 6.20 5.02
3 21.21 4.28 4.96 4.03
4 3.33 3.40 0.98 2.21
Mon Sep 30 15:19:52 EDT 2013
MS-19 Cross Section#5:
Overall Channel ote: coarse . avel channel with ordinary firm loam banks)
r'.
The channel at cross section 5, which has a 1.7 percent slope, contains the following
characteristics:
Channel Bottom:
Description: (coarse gravel)
`n' value for channel bottom: 0.083*
Permissible Velocity: 6.0 ft/s**
Channel Banks:
Description: (ordinary firm loam)
Manning's `n' value for channel banks: 0.045*
Permissible Velocity for channel banks: 3.5 ft/s**
*Manning's `n'values are in accordance with Tables 5-16 through 5-21 of the VESCH.
Please see attached derivations.
**Permissible Velocities are in accordance with Table 5-22 of the VESCH
Maximum Computed Depth=2.31'
Maximum Computed Velocity=4.08 ft/s(channel bottom)
Maximum Computed Velocity=3.20 ft/s(channel banks)
Complex Channnel- Cross Section No. 5
Input:
Slope 0.017
Flow(given) 54.430
line x y n
0 0.000 3.000 0.045 (first n value not used)
1 2.000 1.000 0.045
2 5.000 0.000 0.083
3 8.000 0.000 0.083
4 10.000 3.000 0.045
Output:
Depth 2.312
(Y) ( 2.312)
Channel bed segment output:
line Q V A P
1 2.22 2.58 0.86 1.86
2 18.20 3.35 5.44 3.16
3 28.30 4.08 6.94 3.00
4 5.70 3.20 1.78 2.78
Mon Sep 30 15:23:56 EDT 2013
MS-19 Cross Section#6:
Overall Channel Note: aded loam channel with ordinary firm loam & banks)
• -r
' A . . /MCI . �•
V 4,4
The channel at cross section 6, which has a 2.0 percent slope, contains the following
characteristics:
Channel Bottom:
Description: (graded loam)
`n' value for channel bottom: 0.045*
Permissible Velocity: 5.0 ft/s**
Channel Banks:
Description: (ordinary firm loam)
Manning's `n' value for channel banks: 0.045*
Permissible Velocity for channel banks: 3.5 ft/s**
*Manning's `n' values are in accordance with Tables 5-16 through 5-21 of the VESCH.
Please see attached derivations.
**Permissible Velocities are in accordance with Table 5-22 of the VESCH
Maximum Computed Depth= 1.74'
Maximum Computed Velocity=4.81 ft/s (channel bottom)
Maximum Computed Velocity=2.13 ft/s (channel banks)
Complex Channnel- Cross Section No. 6
Input:
Slope 0.020
Flow(given) 54.431
line x y n
0 0.000 3.000 0.045 (first n value not used)
1 3.000 1.000 0.045
2 6.000 0.000 0.050
3 12.000 1.000 0.050
4 13.000 3.000 0.045
Output:
Depth 1.742
(Y) ( 1.742)
Channel bed segment output:
line Q V A P
1 0.88 2.13 0.41 1.34
2 17.48 4.69 3.73 3.16
3 35.88 4.81 7.45 6.08
4 0.19 1.41 0.14 0.83
Mon Sep 30 15:29:29 EDT 2013
24-Hour SCS Method Calculations
U.S.Department of Agriculture FL-ENG-21A
Natural Resources Conservation Service 06/04
TR 55 Worksheet 2:Runoff Curve Number and Runoff
Project: Avinity(Approved Layout&Potential Future Development) Designed By: FGM,PE Date: 9/3/2013
Location: Located off Avon Street Extended,South of Cale ES Checked By: FGM,PE Date: 9/3/2013
Check One: Present X Developed X
1.Runoff curve Number(CN)
Soil name and Cover description
Drainage Area CN(weighted)=
g (Cover type,treatment,and hydrologic condition; Area Product of Calculated
hydrologic group CN total product/
Description percent impervious;unconnected/connected (Acres) CN x Area 'S'Value
(Appendix A) total areaimpervious area ratio)
D.A#lA Impervious Areas 98 0.20 20.0
(Present)
B Woods in Good Condition 55 8.58 471.7 56.4 7.73
Lawns in Good Condition(75%+Groundcover) 61 0.77 46.9
D.A#1B Impervious Areas 98 0.00 0.0
(Present) B Woods in Good Condition 55 26.26 1444.3 55.0 8.18
Lawns in Good Condition(Approx.15%) 61 0.00 0.0
D.A#1C Impervious Areas 98 0.00 0.0
(Present) B Woods in Good Condition(Approx.25%) 55 2.09 114.7 59.5 6.81
Lawns in Good Condition (Approx.75%) 61 6.26 381.6
D.A.#1A
(Developed) B Approved DA#1A Watershed 81.6 9.11 743.4 81.6 2.25
D.A.1B Impervious Areas 98 0.00 0.0
(Not Modified) B Woods in Good Condition 55 26.26 1444.3 55.0 8.18
Lawns in Good Condition(Approx.15%) 61 0.00 0.0
D.A.1C Impervious Areas(incl.previously bypassed areas) 98 4.63 453.8
B Woods in Good Condition(Approx.25%) 55 0.00 0.0 80.5 2.42
(Developed) Lawns in Good Condition (Approx.75%) 61 4.15 253.1
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 0.47 1.39 D.A#1A(Present)
Runoff,Q-inches 0.42 1.29 D.A#1B(Present)
Runoff,Q-inches 0.60 1.63 D.A#1C(Present)
Runoff,Q-inches 1.92 3.58 D.A.#1A(Developed)
Runoff,Q-inches 0.42 1.29 D.A.1B(Not Modified)
Runoff,Q-inches 1.83 3.47 D.A.1C(Developed)
U.S.Department of Agriculture FL-ENG-21A
Natural Resources Conservation Service 06/04
TR 55 Worksheet 3.Time of Concentration(T J or Travel Time(T,)
Project: Avinity(Approved Layout&Potential Future Development) Designed By FGM,PE Date 9/3/2013
Location: Located off Avon Street Extended,South of Cale ES Checked By FGM,PE Date 9/3/2013
Check One• Present X Developed X
Check One: T, X T, Through subarea n/a
D.A 41A D.A 418 D.A 41C D.A 41A D.A.1B D.A.IC
Segment ID: (Present) (Present) (Present) (Developed) (Not Modified) (Developed)
Sheet Flow:(Applicable to T only)
Dense
1 Surface description(Table 3-1) Grass
2 Manning's roughness coeff.,n(Table 3-1 0 24
3 Flow length,L(total L <100)(ft) 100
4 Two-year 24-hour rainfall,P z(in.) 37
5 Land slope,s(ft/ft) 0 04
6 Compute T,_[0.007(n•L)")/Pz's s°• 0.17
Shallow Concentrated Flow.
7 Surface description(paved or unpaved) Unpaved
8 Flow Length,L(ft) 700
9 Watercourse slope,s(ft/ft) 0.07
10 Average velocity,V(Figure 3-1)(ft/s) 4.2
11 T,=L/3600•V 0.05
Channel Flow:
12 Cross sectional flow area,a(ft ')
13 Wetted perimeter,P„(ft)
14 Hydraulic radius,r=a/P„(ft)
15 Channel Slope,s(ft/ft)
16 Manning's Roughness Coeff,n
17 V=[1.49rV's°s)/n
18 Flow length,L(ft)
19 T,=L/3600•V
20 Watershed or subarea T,or T, Approved Approved Approved Approved Future
(Add T,in steps 6,11 and 19) 0.25 0.42 0.22 0.22 0.42 0.17
(Formerly DABS) (Formerly DA43) (Formerly DA43)
U.S.Department of Agriculture FL-ENG-21C
Natural Resources Conservation Service 06/04
TR 55 Worksheet 4'Graphical Peak Discharge Method
Project: Avinity(Approved Layout&Potential Future Development) Designed By: FGM,PE Date• 9 3 2013
Location Located off Avon Street Extended,South of Cale ES Checked By FGM,PE Date: 9 3 2013
Check One: Present X Developed X
Drainage Drainage Area Drainage Area Drainage Area Drainage Area Drainage Area Drainage Area
1.Data Area Description Description Description Description Description Description
D.A 81A D.A S113 D.A B1C D.A.81A D.A.1B D.A.1C
(Present) (Present) (Present) (Developed) (Not Modified) (Developed)
Drainage Area(Am)in miles '= 0.0149 0.0410 0.0130 0.0142 0.0410 00137
Runoff curve number CN= 56.4 55.0 595 81.6 55.0 80.5
Time of concentration(Tc)= 0.25 0.42 0 22 0.22 0.42 0.17
Rainfall distribution type= II II II II II II
Pond and swamp areas spread
throughout the watershed= 0 0 0 0 0 0
2.Frequency-years 2 10 2 10 2 10 2 10 2 10 2 10
3.Rainfall,P(24 hour)-inches 3.7 5.6 3.7 5.6 3.7 56 3.7 5.6 3.7 5.6 3.7 5.6
4.Initial Abstraction,la-inches 1.546 1.546 1.636 1.636 1.361 1.361 0.451 0.451 1.636 1.636 0.484 0.484
5.Compute la/P 0.42 0.28 0.44 0.29 0.37 0.24 0.12 0.08 0.44 0.29 0.13 0.09
6.Unit peak discharge,Qu-csm/in 475 650 350 500 575 700 750 775 350 500 725 825
7.Runoff,Q from Worksheet 2-inches 0.47 1.39 0.42 1 29 0 60 1.63 1.92 3.58 0.42 1 29 1.83 3.47
8.Pond and Swamp adjustment factor,Fp 1 1 1 1 1 1 1 1 1 1 1 1
9.Peak Discharge,Op-cfs Routed through Routed through Routed through
where Qp=Qu Am Q Fp 3.33 13.53 5.97 2654 4.48 14.84 SWM Facility SWM Facility SWM Facility
NOTE:For SWM Facility routing,the accumulation of post-dev.DA PIA,1B&1C is 44.15 ac.w/Tc=0.42 hrs&CN=65.6
U.S.Department of Agriculture FL-ENG-21A
Natural Resources Conservation Service 06/04
TR 55 Worksheet 2:Runoff Curve Number and Runoff
Project: Avinity-Amended Channel Adequacy Calculations Designed By: FGM,PE Date: 9/27/2013
Location: Located off Avon Street Extended,South of Cale ES Checked By: FGM,PE Date: 9/27/2013
Check One: Present X Developed X
1.Runoff curve Number(CN)
Soil name and Cover description
Drainage Area CN(weighted)=
g (Cover type,treatment,and hydrologic condition; Area Product of Calculated
hydrologic group CN total product/
Description percent impervious;unconnected/connected (Acres) CN x Area 'S'Value
(Appendix A) impervious area ratio) total area
Southern DA Approved CN value of 69-Not modified
(Not Modified) B Approved Soil Type B-Not modified 69 53.07 3661.8 69.0 4.49
Approved DA reduced from 54.94ac.
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 1.08 2.40 Southern DA (Not Modified)
Runoff,Q-inches
Runoff,Q-inches
Runoff,Q-inches
Runoff,Q-inches
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 J or Travel Time(T r)
Project: Avinity-Amended Channel Adequacy Calculations Designed By: FGM,PE Date. 9/27/2013
Location: Located off Avon Street Extended,South of Cale ES Checked By: FGM,PE Date: 9/27/2013
Check One: Present X Developed X
Check One: T, X T, Through subarea n/a
Southern DA
Segment ID• (Not Modified)
Sheet Flow(Applicable to T ,only)
1 Surface description(Table 3-1)
2 Manning's roughness coeff.,n(Table 3-1
3 Flow length,L(total L 100)(ft)
4 Two-year 24-hour rainfall,P r(in.)
5 Land slope,s(ft/ft)
6 Compute Tr=[0.007(n•L)ae]/Pz.s so.e
Shallow Concentrated Flow:
7 Surface description(paved or unpaved)
8 Flow Length,L(ft)
9 Watercourse slope,s(ft/ft)
10 Average velocity,V(Figure 3-1)(ft/s)
11 Tr=L/3600•V 1
Channel Flow:
12 Cross sectional flow area,a(ft ')
13 Wetted perimeter,P (ft)
14 Hydraulic radius,r=a/P w(ft)
15 Channel Slope,s(ft/ft)
16 Manning's Roughness Coeff,n
17 V=[1.49rx sQs]/n
18 Flow length,L(ft)
19 Tr=L/3600•V
20 Watershed or subarea T,or Tr Approved
(Add Tr in steps 6,11 and 19) 0.42
U.S.Department of Agriculture FL-ENG-21C
Natural Resources Conservation Service 06/04
TR 55 Worksheet 4:Graphical Peak Discharge Method
Project: Avinity-Amended Channel Adequacy Calculations Designed By: FGM,PE Date: 9 27 2013
Location' Located off Avon Street Extended,South of Cale ES Checked By: FGM,PE Date: 9 27 2013
Check One: Present X Developed X
Drainage Drainage Area Drainage Area Drainage Area Drainage Area Drainage Area Drainage Area
1.Data Area Description Description Description Description Description Description
(Not
Modified)
Drainage Area(Am)in miles = 0.0829 (Reduced)
Runoff curve number CN= 69.0 (Not Modified)
Time of concentration(Tc)= 0.42 (Not Modified)
Rainfall distribution type= II
Pond and swamp areas spread 0
throughout the watershed=
2 Frequency-years 2 10
3 Rainfall,P(24 hour)-inches 3.7 5.6
4.Initial Abstraction,la-inches 0.899 0.899 (Not Modified)
5.Compute la/P 0.24 0.16 (Not Modified)
6.Unit peak discharge,Qu-csm/in 500 550 (Not Modified)
7.Runoff,Q from Worksheet 2-inches 1.08 2.40 (Not Modified)
8.Pond and Swamp adjustment factor,Fp 1 1
9.Peak Discharge,Qp-cfs
where Qp=Qu Am Q Fp 44.61 109.64 (Reduced)
Routing Calculations
Proposed Retention Basinl0
BasinFlow printout
INPUT:
Basin: Avinity Amended Retention Basin
9 Contour Areas
Elevation(ft) Area(sf) Computed vol . (cy)
493.00 8153.00 0.0
494.00 9021.00 317.9
496.00 10858.00 1053.1
498.00 12834.00 1929.6
499.00 17133.00 2482.6
500.00 18271.00 3138.1
502.00 20651.00 4578.8
504.00 23177.00 6201.1
505.00 24476.00 7083. 5
Start_Elevation(ft) 499.00 vol . (cy) 2482.60
4 Outlet Structures
Outlet structure 0
Orifice
name: Low-Flow Orifices
area (sf) 0.349
diameter or depth (in) 8.000
width for rect. (in) 0.000
coefficient 0.600
invert (ft) 499.000
multiple 4
discharge into riser
Outlet structure 1
weir
name: Emergency Spillway
length (ft) 40.000
side angle 0.000
coefficient 3.300
invert (ft) 503.100
multiple 1
discharge through dam
Outlet structure 2
Culvert
name: Barrel
multiple 1
discharge out of riser
D (in) 30.000
h (in) 0.000
Length (ft) 76.000
Slope 0.005
Manning's n 0.013
Inlet coeff. Ke 0.500
Equation constant set 3
Invert (ft) 494.380
Outlet structure 3
Curve
name: Anti-vortex device
multiple 1
Invert (ft) 501. 500
discharge into riser
file: thirtysix.txt
Page 1
Proposed Retention Basinl0
3 Inflow Hydrographs
Hydrograph 0
SCS
name: 2-yr, 24hr Peak SCS Method Storm
Area (acres) 44.150
CN 65.600
Type 2
rainfall , P (in) 3.700
time of conc. (hrs) 0.4200
time increment (hrs) 0.0200
time limit (hrs) 30.000
fudge factor 1.00
routed true
peak flow (cfs) 31.752
peak time (hrs) 12.066
volume (cy) 5276.469
Hydrograph 1
SCS
name: 10-yr, 24hr Peak SCS Method Storm
Area (acres) 44.150
CN 65.600
Type 2
rainfall , P (in) 5.600
time of conc. (hrs) 0.4200
time increment (hrs) 0.0200
time limit (hrs) 30.000
fudge factor 1.00
routed true
peak flow (cfs) 75.419
peak time (hrs) 12.066
volume (cy) 12533.057
Hydrograph 2
SCS
name: 100-yr, 24hr Peak SCS Method Storm
Area (acres) 44.150
CN 65.600
Type 2
rainfall , P (in) 9.100
time of conc. (hrs) 0.4200
time increment (hrs) 0.0200
time limit (hrs) 30.000
fudge factor 1.00
routed true
peak flow (cfs) 173.887
peak time (hrs) 12.066
volume (cy) 28896.295
OUTPUT:
Routing Method: storage-indication
Hydrograph 0
Routing Summary of Peaks: 2-yr, 24hr Peak SCS Method Storm
inflow (cfs) 31.624 at 12.06 (hrs)
discharge (cfs) 9.824 at 12.46 (hrs)
water level (ft) 501.470 at 12.46 (hrs)
storage (cy) 4179.972
Hydrograph 1
Routing Summary of Peaks: 10-yr, 24hr Peak SCS Method Storm
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Proposed Retention Basinl0
inflow (cfs) 75.116 at 12.06 (hrs)
discharge (cfs) 52.378 at 12.22 (hrs)
water level (ft) 503.113 at 12.22 (hrs)
storage (cy) 5458.196
Hydrograph 2
Routing Summary of Peaks: 100-yr, 24hr Peak SCS Method Storm
inflow (cfs) 173.188 at 12.06 (hrs)
discharge (cfs) 169.168 at 12.10 (hrs)
water level (ft) 503.943 at 12.10 (hrs)
storage (cy) 6151.967
Thu Aug 29 15:53:43 EDT 2013
Page 3