HomeMy WebLinkAboutDrainage ReportDrainage Report
for
Spring Creek Townhomes Subdivision
Phase 4
College Station, Texas
May 2006
Developer:
Spring Creek CS Development, Ltd.
4490 Castlegate Drive
College Station ~ Texas 77845
(979) 690-7250
Prepared By:
Civil Developn1ent, Ltd.
2900 Longmire Drive, Suite K
College Station, Texas 77845
(979) 764-7743
Prepared for Te.ff'0/1 Gen ral Cn111rnctor.1
CERTIFICATION
I, Joseph P. Schultz, Licensed Professional Engineer No. 65889, State of Texas, certify that this
repo1i for the drainage design for the Spriug Creek Towulwmes Subdivision -Phase 4, was
prepared by me in accordance with the provisions of the City of College Station Drainage Policy
and Design Standards for the owners hereof.
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TABLE OF CONTENTS
SPRING CREEK TOWNHOMES SUBDIVISION -PHASE 4
CERTIFICATION ................................................................................................................................................................. 1
TABLE OF CONTENTS ....................................................................................................................................................... 2
LIST OF TABLES .................................................................................................................................................................. 2
INTRODUCTION .................................................................................................................................................................. 3
GENERAL LOCATION AND DESCRIPTION ................................................................................................................. 3
FLOOD HAZARD INFORMATION ................................................................................................................................... 3
DETENTION FACILITY ...................................................................................................................................................... 3
DEVELOPMENT DRAINAGE PATTERNS ...................................................................................................................... 3
DRAINAGE DESIGN CRITERIA ....................................................................................................................................... 4
STORM WATER RUNOFF DETERMINATION .............................................................................................................. 5
I STORM SEWER DESIGN .................................................................................................................................................... 6
FLOOD HAZARD AREA DETERMINATION ................................................................................................................. 6
CONCLUSIONS ..................................................................................................................................................................... 7
APPENDIX A ......................................................................................................................................................................... 8
Time of Concentration Equations & Calculations
APPENDIX B ........................................................................................................................................................................ 11
Storm Inlet Design Data & Calculations
APPENDIX C ....................................................................................................................................................................... 14
Storm Pipe Design Data & Calculatio11s
APPENDIX D ....................................................................................................................................................................... 19
HEC-RAS Data & Calculatio11s
EXHIBIT A ........................................................................................................................................................................... 21
Post-Developme11t Drai11age Area Map -Street & Storm Sewer Design
EXHIBIT B ........................................................................................................................................................................... 23
Post-Development Drainage Area Map -Floodplain Analysis
LIST OF TABLES
TABLE 1 -Rainfall Intensity & Runoff Data ..................................................................................... 4
TABLE 2 -Time of Concentration (tc) Equations .............................................................................. 5
TABLE 3 -Post-Development Drainage Data -Storm Sewer. .......................................................... 5
TABLE 4 -Drainage Channel Design Data ......................................................................................... 6
DRAINAGE REPORT
SPRING CREEK TOWNHOMES SUBDIVISION -PHASE 4
INTRODUCTION
The purpose of this report is to provide the hydrological effects of the construction of the
Spring Creek Townhomes Subdivision -Phase 4, and to verify that the proposed stom1
drainage system meets the requirements set forth by the City of College Station Drainage
Policy and Design Standards.
GENERAL LOCATION AND DESCRIPTION
The project is located on a portion of a 19.0 acre tract located north of Greens Prairie Road
along the West Frontage Road of State Highway 6 in College Station, Texas. This report
addresses Spring Creek Townhomes, Phase 4. The site is pastureland with some wooded
areas. The existing ground elevations range from Elevation 269 to Elevation 280. The
general location of the project site is shown on the vicinity map in Exhibit A.
FLOOD HAZARD INFORMATION
The project site is located in the Spring Creek branch of the Lick Creek Drainage Basin.
As shown on Exhibit A, a portion of the site is located within a special flood hazard area
according to the Flood Insurance Rate Map prepared by the Federal Emergency
Management Agency (FEMA) for Brazos County, Texas and incorporated areas dated
February 9, 2000, panel numbers 48041C0205-D and 48041C0201 -D. A Conditional
Letter of Map Revision (CLOMR) was prepared and submitted to FEMA by LJA
Engineering & Surveying for the construction of the detention pond, drainage channels and
roadway culverts on Spring Creek and its tributaries. From this study, construction
drawings of the detention pond and drainage channels were prepared for these structures to
be constructed on the Crowley property were prepared. These drawings included the
extension of the drainage channel adjacent to this tract. With the construction of this
channel, the 100-year floodplain is now contained within the limits of the channel.
In order to demonstrate that the 100-year Flood Hazard Area does not encroach on this
tract, hydro logic and hydraulic analyses of Spring Creek Tributary C were performed.
Details of this analysis are presented in subsequent sections of this report. Also, a LOMR
is being prepared for the Crowley Tract, which will include this channel in the area studied
and the revjsed 100-year floodplain limits will be shown for this tract.
DETENTION FACILITY
Storn1 water detention for this site is provided by the existing detention facility on the
Crowley Tract. This detention facility was designed to control the increased run off from
th e development of this tract.
DEV ELOPMENT DRAINAGE PATTERNS
Pre-development runoff from this site fl ows in an easterl y and southeas terly direction until
it enters either Tributary C of Spring Creek or the Arrington Road right-of-way. Much of
the post-development runoff is also captured by these two facilities, but a portion is also
captured by the proposed street and storm sewer in the subdivision.
DRAINAGE DESIGN CRJTERIA
The Rational Equation was used to determine the peak flow for the stom1 sewer desi gn.
The design parameters for the storm sewer are as follows:
• Design Storm Frequency
Storm Sewer system 10 and 100-year stom1 events
• Runoff Coefficients
Single Family Residential (Townhomes)
Single Family Residential (Patio Homes)
c = 0.65
c = 0.55
• Rainfall Intensity equations and values for Brazos County can be found in Table 1.
• Time of Concentration, tc -Calculations are based on the method found in the TR-55
publication. Refer to Table 2 for the equations and Appendix A for calculations. The
runoff flow paths used for calculating the times of concentration are shown on each of
the exhibits. For smaller drainage areas, a minimum tc of 10 minutes is used to
determine the rainfall intensity values.
• Due to the size of the Spring Creek Tributary C drainage basin, the HEC-1 computer
program was used to evaluate the peak discharge for the existing floodplain.
• Runoff Curve Number (CN) -Floodplain Evaluation
The Brazos County Soil Survey shows the soils in the area to be classified as
hydrologic Group D soils. The post-development CN is based on development of
the project.
TABLE 1-Rainfall Intensity & Runoff Data
Rainfall Intensity Values
(in/hr)
Storm tc =
Event 10 min
Is 7.693
110 8.635
l2s 9.861
lso 11 .148
1100 11 .639
Brazos
County:
5 If.ear storm 10 If.ear storm
b= 76 b= 80
d= 8.5 d = 8.5
e = 0.785 e = 0.763
I = b I (tc+d)e
I = Rainfall Intensity (in/hr)
tc = U(V*60)
tc = Time of concentration (min)
L = Length (ft)
V =Velocity (ft/sec)
25 If.ear storm 50 If.ear storm 100 If.ear storm
b= 89 b= 98 b= 96
d= 8.5 d = 8.5 d = 8.0
e = 0.754 e = 0.745 e = 0.730
(Data taken from State Department of Hiqhwa'f.s and Public Transportation H'f.draulic Manual, pag e 2-16)
-1
TABLE 2 -Time of Concentration (tc) Equations
Th e time of concentration was determined using methods f ound in TR-55, "Urban
Hydrology for Small Wat ersheds. " Th e equations are as f ollows:
Time of Concentration:
For Sheet Flow:
For Shallow Concentrated Flow:
Tc = T1(shec1 now)+ T1(conccnlralcd sheel flow)
where: T1 =Travel Time, minutes
where: T1 = travel time, hours
n =Manning's roughness coefficient
L = flow length, feet
P2 = 2-year, 24-hour rainfall = 4.5"
s = land slope, ft/ft
T1 = L I (60*V)
where: T1 = travel time, minutes
V =Velocity, fps (See Fig 3-1 , App. A)
L = flow length, feet
Refer to Appendix A for calculations.
STORM WATER RUNOFF DETERMINATION
The peak runoff values were determined in accordance with the criteria presented in the
previous section for the 5, 10, 25, 50, and 100-year storm events. The runoff coefficients
are based on the development of this tract. Exhibit A shows the post-development
drainage area for the storm sewer design, and the data for this area is summarized in Table
3.
TABLE 3 -Post-Development Drainage Data -Storm Sewer
Area c 5 year storm 10 year storm 25 year storm 50 year storm 100 year storm tc Area# (acres) Is
A1 I A2 I Total
C1 C2 Cr.,., (min) (in/hr)
1 0.54 I 1.97 I 2.51 0.55 0.65 0.63 38.6 3.694
The Rational Method:
Q =CIA I = b I (tc+d)0
Q =Flow (cfs)
A= Area (acres)
C = Runoff Coeff.
le= Time of concentration (min)
I = Rainfall Intensity (in/hr)
Brazos County:
51-:ear storm 1 O 1-:ear storm 25 1-:ear storm
b = 76 b = 80 b = 89
d = 8.5 d = 8.5 d = 8.5
e = 0.79 e = 0.76 e = 0.75
Os
(cfs)
5.83
110 0 10
(in/hr) (cfs)
4.232 6.68
tc = U(V*60)
L = Length (ft)
l2s 02s 150
(in/hr) (cfs) (in/hr)
4.875 7.69 5.557
V =Velocity (ft/sec)
50 1-:ear storm 100 1-:ear storm
b = 98 b = 96
d = 8.5 d = 8.0
e = 0.745 e = 0.730
Oso 1100
(cfs) (in/hr)
8.77 5.812
The drainage area used in the floodplain analysis along the channel is shown on Ex hibit B.
Table 4 shows th e dra in age data for Area C2. This data is from th e Oxburgh Dri ve, Ph ase I
Drainage Report, prepared in December, 2002. The runoff rrorn this area was previously
computed usin g th e H EC-I model ror th e design of th e Arrington Road cul verts.
0 100
(cfs)
9.17
TABLE 4 -Drainage Channel De sign Data
Drainage Area
No. I (acres) I (sq. mi.)
C-2 I 122.90 I 0.1920
HEC-1 Peak Runoff value:
0100 = 682 cfs
Lag Time SGS Curve
(hrs) Number, CN
0.22 80.9
Note: This data was taken from the design of Culvert No 2 design from the Oxburgh
Drive, Phase 1 Drainage Report prepared in December, 2002.
STORM SEWER DESIGN
The storm sewer piping for this project has been selected to be Reinforced Concrete Pipe
(RCP) meeting the requirements of ASTM C-76, Class III pipe. The curb inlet wi 11 be
cast-in-place concrete. Appendix B presents a summary of the storm sewer inlet design
parameters and calculations. The inlet was designed based on a 10-year design storm.
The inlet was located to maintain a gutter flow depth of 5" or less, which will prevent the
spread of water from reaching the crown of the road for the 10-year storm event. Refer to
Appendix B for a summary of the gutter flow depths at various locations. The runoff
intercepted by the proposed storm sewer inlet was calculated using the following
equations. The depth of flow in the gutter was determined by using the Straight Crown
Flow equation. The capacity for the inlet in sump (Inlet 1) was calculated using the Inlets
in Sumps, Weir Flow equation with a maximum allowable depth of 7" (5" gutter flow plus
2" gutter depression). These equations and the resulting data are summarized in Appendix
B. There are no proposed inlets on grade for this phase of the development. The area
between the right-of-way and the curb line of the streets will be filled as necessary to
provide a minimum of 6" of freeboard above the curb line. This will ensure that the runoff
from the 100-year storm event will remain within the street right-of-way.
Appendix C presents a summary of the stom1 sewer pipe design parameters and
calculations. The pipe for the stom1 sewer system was designed based on the 10-year
storm event; however, it will also pass the 100-year stom1 event without any headwater
under gravity flow conditions. As required by College Station, the velocity of flo w in the
storm sewer pipe system is not lower than 2.5 feet per second, and it does not exceed 15
feet per second. As the data shows, even during low tlow conditions, the velocity in the
pipes will exceed 2.5 feet per second and prevent sediment build-up in the pipes.
Appendix C contains a summary of the Manning pipe calculations for the storm sewer
system for the 10 and 100-year events. The maximum velocity for the pipe system will be
6.8 feet per second.
The stonn sewer pipe system di scharges the runoff into th e ex isting detention pond. Rock
riprap will be pl aced at th e encl of th e headwall to prevent erosion.
FLOOD HAZARD AREA DETERMINATION
The H EC-RAS co mputer model was used to determine th e I 00-year water surf;1ce
elcv;1t ion in th e ex isting clrnnncl ;1dj ;1cent to thi s tract. As previo usly noted , th e pc;11'
APPENDIX A
Time of Concentration Equations & Calculations
runoff of 682 cfs from the Oxburgh Drive Drainage Report was used for the modeling of
the channel.
The limits of the floodplain computed by the HEC-RAS model are within the banks of the
existing channel and do not encroach on the Spring Creek Townhomes, Phase 4 project. A
summary of the HEC-RAS results is shown in Appendix D.
CONCLUSIONS
The construction of this project will increase the stom1 water runoff from this site. The
runoff will be collected in the street gutters and directed into the proposed storm sewer
system, which will adequately control the runoff and release it into the existing detention
pond. The existing drainage channel adjacent to this site on Tributary C is sized to handle
the 100-year stom1 runoff. Also, the regional detention facility should adequately reduce
the peak post-development runoff to less than the pre-development runoff for the design
storm event for this project. This should prevent any impact on the properties downstream
of this project.
Tc Calculations-Post Development
Drainage Area No. 1 (2.51 acres)
Tc from Spring Crk Gardens Ph 2 =._I __ 3_6_.0_m_i_n __ __,
Gutter Flow 1: V= 3.1 fps (paved)
L= 310 Elev1= Slope= 0.0200
L/(60*V) = 1.6 min
Gutter Flow 2: V= 2.4 fps (paved)
L= 142 Elev1= Slope= 0.0130
L/(60*V) = 1.0 min
38.6 min
NOTE: There is bypass· flow from existing Inlets 4 & 5 on Whispering Creek Drive that flows
into this project. The storm sewer design of Spring Creek Gardens, Phase 2, uses a time of
concentration, Tc, of 36.0 minutes at these inlets. Calculations for this time can be found in the
Drainage Report for Phase 2 of Spring Creek Gardens. The flow time of 2.6 minutes from these
inlets to proposed Inlet 1 was added to 36.0 minutes to get the design Tc of 38.6 minutes.
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APPENDIXB
Storm Inlet Design Data & Calculations
11
Spring Creek Townhomes Subdivision, Phase 4
Depth of Flow in Street Gutter
10-year storm
Gutter A c Tc Slope 0 10 Y10-actual
Location (acres) (min) (ft/ft) (cfs) (ft) (in)
A1 0.52 0.63 10.0 0.0132 2.83 0.246 2.95 -----A2 1.99 0.63 38.6 0.0132 5.31 0.311 3.74
For 10-year storm event, there is no bypass from existing Inlets 4 & 5.
Transverse (Crown) slope (ft/ft)
27' street = 0.0300 0.0300
Straight Crown Flow (Solved to find actual depth of flow in gutter, y):
Q = 0.56 * (z/n) * S112 * ys1J ~ y ={Q I [0.56 * (z/n) * S112]}J1s
n = Roughness Coefficient= 0.018
S = Street/Gutter Slope (ft/ft)
y = Depth of flow at inlet (ft)
z = Reciprocal of crown slope:
27' street = 33 33
Spring Creeek Townhomes -Phase 4
Inlet Length Calculations
Inlet#
1
Length
10'
Inlets In Sump
Flow from A c
Area# (acres)
1-lefl 0.52 0.63
1-right 1.99 0.63
Transverse (Crown) slope (ft/ft)
for 27' street = 0.030
Tc Q,.
(min) (els)
10.0 2.83
38.6 5.31
Straight Crown Flow (Solved to find actual depth of flow, y}:
Q = 0.56 • (z/n) • S112 • y813 Q y ={Q I [0.56 • (z/n) • S112)}318
n = Roughness Coefficient = 0.018
S = StreeVGutter Slope (ft/ft)
y = Depth of flow at inlet (ft)
Capacity of Inlets on grade:
Oc = 0.7 • [1/(H1 -H2)] • [H1512-H2 512]
Oc = Flow capacity of inlet (cfs)
H, =a+ y
H2 = a = gutter depression (2" Standard; 4" Recessed)
y = Depth of flow in approach gutter (ft)
Bypass for Inlet 4: Bypass for Inlet 5:
0 10 = 0 cfs; 0 100 = 2.25 cfs 010 = 0 cfs; 0 100 = 0.37 cfs
(els)
0.00
0.00
10 year storm
Q CWf)'O¥ef Orot., O rotlf•10% Y10..ctu.i
from Inlet# (els) (els) (ft)
2.83 3.11 0.219
5.31 5.84 0.277
z = Reciprocal of crown slope
for 27' street = 33
Inlets In sumps, Weir Flow:
L = Q I (3 • y312) Q y = (Q I 3L)v3
L = Length of inlet opening (fti
0 = Flow at inlet (cfs)
y = total depth of flow on inlet (ft)
max y for inlet in sump= 7" = 0.583'
(In)
2.62
3.32
100 year storm
L10-R~'' L10-.ctu.i o, .. O cwryoY•f Orot.i Orotal•10% y,.,
(ft) (ft) (els) (els) from Inlet# (els) (els) (ft) (In)
4.18 0.00 4.18 4.60 0.633 7.59 6.70 10 9.54 0.00 9.54 10.49
•using y .... a r. 0.583'
APPENDIXC
Storm Pipe Design Data & Calculations
l..J
Spring Creeek Townhomes -Phase 4
Flow for Pipe Design
Pipe# Area #'s
13 1, bypass of 1-4 & 1-5 from Ph 2 Gardens
Bypass for Inlet 4:
0 10 = 0 cfs; 0 100 = 2.25 cfs
Bypass for Inlet 5:
0 10 = O cfs; 0 100 = 0.37 cfs
The Rational Method:
Q=CIA
Q = Flow (cfs)
A = Area (acres)
C = Runoff Coeff.
I = Rainfall Intensity (in/hr}
Area c
(acres)
A1 I I Total
C1 Cz Crotal Az
o.54 I 1.97 I 2.51 0.55 0.65 0.63
I = b I (tc+d}e
le= Time of concentration (min)
Brazos County:
10 year storm
b = 80
d = 8.5
e = 0.763
100 year storm
b = 96
d = 8.0
e = 0.730
tc
10 year storm
110
(min) (in/hr)
38.6 4.232
tc = L/(V*60)
L = Length (ft)
010
(cfs)
6.68
V =Velocity (fUsec)
100 year storm
1100 0 100
(in/hr) (cfs)
5.812 11 .79
Spring Creek Townhomes Subdivision -Phase 4
Pipe Calculations
Inlet Outlet 10 year storm 100 year storm
Pipe# Size Length Slope Invert Invert *Actual Design Mannings *Actual Design Mannings
Elevation Elevation Flow Flow V10 Travel Time, tno Flow Flow V100 % Full % Full (in) (ft) (%) (ft) (ft) (cfs) (cfs) (fps) (sec) I (min) (cfs) (cfs) (fps)
13 24 128.0 0.80 266.46 265.44 6.68 10.79 6.2 54.3 21 I 0.34 11 .79 19.04 5.8 83.2
*This value reflect the actual flow for the 24" pipe . The design flow for this pipe size reflects a 25% reduction in pipe area.
(Refer to attached calculation for specific information.)
Travel Time, tnoo
(sec) T (min)
22 I 0.37
City of College Station requirement to Reduce Cross-Sectional Area of 18" & 24" Pipes by 25%
Using Mannings Equation from page 48 of the College Station Drainage Policy & Design Standards Manual:
Q = 1.49/n * A * R2t3 * S 112
Q =Flow Capacity (cfs)
18" Pipe:
Pipe size (inches) =
Wetted Perimeter WP• (ft) =
Cross-Sectional Area A, (W) =
Reduced Area AR, (ft2) =
Hydraulic Radius R = /VVVP, (ft)=
Reduced Hydr Radius RR = ARIW P• (ft) =
Roughness Coefficient n =
Friction Slope of Conduit Sr. (ft/ft) =
Example Calculation:
Slope Flow Capacity Reduced Flow Capacity
s Q
0.005 6.91
0.006 7.57
0.007 8.18
24" Pipe:
Pipe size (inches)=
Wetted Perimeter W P• (ft) =
Cross-Sectional Area A, (W) =
Reduced Area AR, (ff) =
Oreduced
4.28
4.69
5.06
Hydraulic Radius R = /VVVP, (ft)=
Reduced Hydr Radius RR = AR/WP· (ft) =
Roughness Coefficient n =
Friction Slope of Conduit Sr. (ft/ft) =
Example Calculation:
Slope Flow Capacity Reduced Flow Capacity
s Q Oreduced
0.005 14.89 9.22
0.006 16.31 10.1
0.007 17.61 10.9
Conclusion:
18
4.71
1.766
1.325
0.375
0.281
0.014
0.01
% Difference
OreduceiO
0.619
0.619
0.619
24
6.28
3.14
2.355
0.5
0.375
0.014
0.01
% Difference
Oreduced/Q
0.619 --------0.619
0.619
Multiply actual Q in 18" & 24" pipes by 1.615 to reflect a 25% reduction in the
cross-sectional area called for on page 4 7, paragraph 5 of the College Station
Drainage Policy & Design Standards manual.
Pipe 13 -10 Year Storm
Manning Pipe Calculato r
Giv en Input Data:
Shape .......................... .
Solving for .................... .
Diameter ....................... .
Flowrate ....................... .
Slope .......................... .
Manning's n .................... .
Computed Results :
Depth .......................... .
Area ........................... .
Wetted Area .................... .
Wetted Perimeter ............... .
Perimeter ................. 1 • • • • • •
Velocity ....................... .
Hydraulic Radius ......... ~ ..... .
Percent Full ................... .
Full flow Flowrate ............. .
Full flow vel ocity ............. .
Circular
Depth of Flow
24.0000 in
10.7900 cfs
0.0080 ft/ft
0. 0140
13.0408 in
3.1416 ft2
1. 7441 ft2
39.7834 in
75 .3982 in
6.1867 fps
6.3128 in
54.3369 %
18.7888 cfs
5.9807 fps
Pipe 13 -100 Year Storm
Manning Pipe Calculator
Given Input Data:
Shape .................... , ..... .
Solving for .................... .
Diameter ....................... .
Flowrate ................. : ..... .
Slope .......................... .
Manning ' s n .................... .
Computed Results:
Depth .......................... .
Area ........................... .
Wetted Area .................... .
Wetted Perime ter ............... .
Perimeter ...................... .
Velocity ....................... .
Hydraulic Radius ............... .
Percent Full ................... .
Full flow Flowrate ............. .
Full flow velocity ............. .
Circular
Depth of Flow
24.0000 in
19.0400 cfs
0 .0080 ft/ft
0. 0140
19.9745 in
3 .1416 ft2
2.7943 ft2
55.1442 in
75 .3982 in
6.8140 fps
7.2967 in
83.2271 %
18 .7888 cfs
5.9807 fps
Spring Creek To1v11!1omes Subdivision -Phase .J
Co llege Statio n, Te~as
APPENDIXD
HEC-RAS Data & Calculations
19
HEC-RAS Model Summary
Spring Creek Trib C
HEC-RAS Plan: oxburg River: Trib C Reach: upper Profile: 1.0 %
Reach River Sta Q Total I Min Ch El lW.S. Elev! Crit w.s. I E.G. Elev .G. Slop
( cfs) (ft) (ft) (ft) (ft) (ft/ft)
upper 1600 682 211.001 273.95i 273.64 274.131 0.004616
upper 1436 682 269.031 271 .97 1 271 .97 272.77 0.016983
upper 1408 682 269.00 271.11 1 27 1.41 272.38 0.009035 1
upper 1372 682 268.10 269.87 270.48 271 .87 0.01 6434
upper 1359 682 265.00 266.27 267.49 271 .23 0.049548
upper 1309 682 265.00 268.39 267.47 268.75 0.003059
upper 1221 682 264.00 267.98 267.03 268.38 0.005768
upper 1083 682 263.00 266.64 266.22 267.27 0.011 212
upper 1043 682 261 .90 266.52 264.66 267.02 0.003032
upper 993 Arrington Road: 3-8'x4' Box Culverts
upper 941 682 261 .00 264.991 263.77 1 265.661 0.005195 I
840 264.11 I ' I upper 682 261 .00 264.11 265.01 0.007772
upper 583 682 259.00 262.29 262.08 263.01 0.005717
upper 267 682 258.00 260.37 260.24 261.1 0.006358
upper 0.1 682 256.00 259.92 258.36 260.05 0.002002
Vel Chnl Flow ArealTop Width Froude #
(ft/s) (sq ft) (ft) Chi
4.21 ! 285.34 285.70 0.50
7.30 ! 103.15 75.49 0.94
9.041 75.58 54.90 1.32
11.36 60.02 45.75 1.75
17.87 1 38.16 33.44 2.95
4.791 142.24 60.76 0.55
5 081 134.1 2 54.72 0.57
6.391 106.721 50.88 0.78
5.68 120.17 52.67 0.47
6.591 103.56 58.05 0.58
7.60 1 89.73 50.94 1.01
6.84 99.71 52.63 0.88
6.901 98.91 55.991 0.91
2.92 233.93 100.31' 0.34
EXHIBIT A
Post-Development Drainage Area Map -Street & Storm Sewer Design
21
EXHIBI11 B
Post-Development Drainage Area Map -Floodplain Analysis
2.1
j
, I
j
1