HomeMy WebLinkAboutPD 2021-0040; 789 PALM AVENUE; DRAINAGE REPORT; 2022-10-28
786 Palm Avenue
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Table Of Contents
Chapter 1 – Discussion ..................................................................................................................3
1.1 Vicinity Map ...............................................................................................................4
1.2 Purpose And Scope ...................................................................................................5
1.3 Project Description ....................................................................................................5
1.4 Existing Conditions ....................................................................................................5
1.5 Developed Conditions ...............................................................................................6
1.6 Summary of Results ...................................................................................................7
1.7 Study Method .............................................................................................................7
1.8 Conclusion ..................................................................................................................8
1.9 Declaration Of Responsible Charge ......................................................................10
Chapter 2 – Existing & Developed Hydrology Maps ................................................................11
Chapter 3 – 100-Year Peak Flow Calculations..........................................................................12
3.1 Existing Hydrology Calculations ............................................................................13
3.2 Developed Hydrology Calculations . .....................................................................15
3.3 Vegetated Swale Calculations . ..............................................................................20
3.4 Volumetric and Flow Calculations for Attenuation of Developed Runoff . .....28
Chapter 4 – References ................................................................................................................30
4.1 Methodology- Rational Method Peak Flow Determination ...............................31
786 Palm Avenue
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CHAPTER 1
DISCUSSION
786 Palm Avenue
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1.1 Vicinity Map
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1.2 Purpose And Scope
The purpose of this report is to publish the results of hydrology and hydraulic computer
analysis for the development of 786 Palm Avenue, located in the City of Carlsbad. The
proposed project is a 0.16-acre site. The scope is to study the existing and proposed
hydrology and hydraulics as it influences the surrounding properties during a 100-year
frequency storm event (Q100), and make recommendations to intercept, contain and convey
Q100 to the historic point of discharge.
1.3 Project Description
The 786 Palm Avenue Project proposes the construction of two (2) separate single-family
two-story residential buildings with associated improvements on two (2) assessor’s parcel
numbers (APN) APN 204-171-10 and APN 204-171-11. Additionally, an accessory dwelling
unit is proposed on the second story of each residential building. The project site,
comprised of APN 204-171-10 and APN 204-171-11, is 0.16‐acres and an existing residential
dwelling (to be demolished) occupying portions of both APNs. The existing project site is
adjacent to Palm Avenue to the south, and alley to the west, and Jefferson Street to the east.
Topographically, the generally rectangular-shaped APNs are characterized by flat grades
sloping in a southwest direction from the northwest corner to the southwest corner of the
project. Elevations range from a high of approximately 59 feet near the northeast corner of
APN 204-171-10 and to a low of approximately 55 feet near the southwest corner of APN
204-171-11. The site drains towards the intersection of Palm Avenue and the Alley.
Vegetation consists of shrubs, grasses, and trees. The onsite soil classification is Type B as
determined from USDA Web Soil Survey (see References).
1.4 Existing Conditions
Storm flows affecting the site are limited to the rainfall that lands directly on the properties.
In the existing condition, surface runoff sheet flows in a southwesterly direction from Node
10 to one (1) Point of Compliance (POC 1) at Node 30. POC 1 is located near the southwest
corner of the project, near the intersection of Palm Avenue and the alley. Excessive
scouring or erosion is not present.
The Existing Hydrology Exhibit shows runoff basins that will drain towards POC 1 (Node
30).
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Table 1 summarizes the existing runoff information from the site. Refer to the Existing
Hydrology Exhibit for drainage patterns, areas, and POC.
Table 1 - Summary of Existing Peak Flows
Discharge Location Drainage Area
(ac)
100-Year Peak Flow
(cfs)
NODE 30 0.24 0.48
Existing Condition 100-Year Peak Flow
1.5 Developed Conditions
The 786 Palm Avenue Project proposes the construction of two (2) separate single-family
two-story residential buildings with associated improvements on two (2) separate APNs.
The majority of stormwater runoff from the project will be intercepted by vegetated yard
swale around each single-family residential building that will direct runoff to a curb outlet to
Palm Avenue for APN 204-171-10 and an infiltration basin to the Alley for APN 204-171-11.
The remaining runoff will be directed onto vegetation and permeable pavers before
discharging onto Jefferson Street, Palm Avenue or the Alley. Permeable pavers will provide
dispersion and infiltration underneath the gravel section of the permeable pavers. For the
purposes of this report, runoff was modeled as draining in a similar direction as the existing
runoff condition, from the northeast corner of the project, Node 10, to the southwest corner
of the project, near the intersection of Palm Avenue and the alley. Node 60 to Node 70, the
northerly portion of APN 204-141, drains to the alley.
Developed site flow will mimic existing drainage conditions. Impervious surfaces have been
minimized where feasible.
Table 2 & 3 summarizes the expected cumulative 100-year peak flow rates. Refer to the
Developed Hydrology Map for drainage patterns, areas, and Points of Compliance.
Table 2 - Summary of Developed Peak Flow
Discharge Location Drainage Area
(ac)
100-Year Peak Flow
(cfs)
Node 0.24 0.55
Developed Condition 100-Year Peak Flow
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1.6 Summary of Results
Table 3 compares the cumulative existing and developed peak flow conditions.
Table 3 - Summary of Existing vs Developed Peak Flows
Drainage Area
(ac)
100-Year Peak Flow
(cfs)
Difference 0.00 -0.01
Attenuated
Developed
Condition
0.24 0.47
Existing
Condition 0.24 0.48
Developed
Condition 0.00 0.55
1.7 Study Method
The method of analysis was based on the Rational Method according to the San Diego
County Hydrology Manual (SDCHM). The Hydrology and Hydraulic Analysis were done
on Hydro Soft by Advanced Engineering Software 2014. The study considers the runoff for
a 100-year storm frequency.
Methodology used for the computation of design rainfall events, runoff coefficients, and
rainfall intensity values are consistent with criteria set forth in the “2003 County of San
Diego Drainage Design Manual.” A more detailed explanation of methodology used for
this analysis is listed in Chapter 5 – References of this report.
Drainage basin areas were determined from the topography and proposed grades shown on
the Grading Plan.
The Rational Method for this project provided the following variable coefficients:
Rainfall Intensity – Initial time of concentration (Tc) values based on Table 3-2 of the
SDCHM. Rainfall Isopluvial Maps from the SDCHM were used to determine P6 for 100-
year storm, see References. Precipitation values were verified with the values obtained
from NOAA website at the coordinates of the project (Chapter 5 - References).
I = 7.44x(P6)x(Tc)- 0.645
P6 for 100-year storm =2.66 inches
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Runoff Coefficient - In accordance with the County of San Diego standards, runoff
coefficients were based on land use and soil type. The soil conditions used in this study are
consistent with Type-B soil qualities. An appropriate runoff coefficient (C) for each type of
land use in the subarea was selected from Table 3-1 of SDCHM and multiplied by the
percentage of total area (A) included in that class. The sum of the products for all land uses
is the weighted runoff coefficient (∑[CA]).
The Developed Hydrology Exhibit shows the offsite area, proposed on-site drainage system,
on-site subareas, and nodal points. Table 5 summarizes the composite C-values calculated in
the existing and proposed conditions.
Table 5 - Composite Runoff Coefficient Value Calculations
Up Node Down Node Total Area (ac)C1 A1 (AC)C2 A2 (AC)CCOMP
10 20 0.061 0.25 0.042 0.90 0.019 0.46
20 30 0.184 0.25 0.126 0.90 0.057 0.45
Notes: C-values taken from Table 3-1 of San Diego County Hydrology Manual, consistent with on-site
existing soil types from the USDA Web Soil Survey. See References.
Up Node Down Node Total Area (ac)C1 A1 (AC)C2 A2 (AC)CCOMP
10 20 0.058 0.25 0.041 0.90 0.017 0.44
20 40 0.049 0.25 0.016 0.90 0.034 0.69
30 40 0.032 0.25 0.018 0.90 0.013 0.52
40 50 0.069 0.25 0.042 0.90 0.028 0.51
60 70 0.037 0.25 0.024 0.90 0.013 0.48
Notes: C-values taken from Table 3-1 of San Diego County Hydrology Manual, consistent with on-site
existing soil types from the USDA Web Soil Survey. See References.
1.8 Conclusion
As shown in Table 4, the development of the proposed 786 Palm Avenue project site will
decrease the runoff by 0.01 cfs during a 100-year storm event. The permeable pavers and
bioretention basin (trash capture BMP) will slow runoff discharges by storing runoff in the
gravel sections underneath them to allow infiltration into the onsite soils beneath, further
decreasing runoff to maintain the existing hydrology.
The 786 Palm Avenue project satisfies the drainage requirements of the City of Carlsbad.
All storm drain facilities have been sized to convey the 100-year storm event without any
adverse effects. Based on this conclusion, runoff released from the proposed project site
will unlikely cause any adverse impact to downstream water bodies or existing habitat
integrity. Sediment will likely be reduced upon site development.
Side yard vegetated swales adjacent to each building will drain not less than 2% away from
the building and not less than 1% longitudinal slope. See vegetated swale calculations in
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Chapter 3 showing that the vegetated swales can adequately convey the calculated runoff for
each lot at longitudinal slopes between 1% to 2% and sides slopes between 2% and 5%.
Peak flow rates listed above were generated based on criteria set forth in SDCHM presented
in Chapter 4 of this report.
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Chapter 2
Existing & Developed Hydrology Maps
SMH
51.19 FLSMH
48.10 FL
30
0.49
0.106
LEGEND
CC=0.34
EL=54.80
RONALD L.
HOLLOWAY
NO. 29271
K:\Civil 3D\1501\DWG\HYDRO\1501 - EXIST HYDROLOGY.dwg, 8/24/2022 9:12:34 AM
SMH
51.19 FLSMH
48.10 FL
UP
UP
A
B
30
0.57
0.188
LEGEND
CC=0.57
RONALD L.
HOLLOWAY
NO. 29271
A
K:\Civil 3D\1501\DWG\HYDRO\1501 - PROP HYDROLOGY.dwg, 8/24/2022 9:33:32 AM
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Chapter 3
100-Year Peak Flow Calculations
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3.1 Existing Hydrology Calculations
100-Year Storm
____________________________________________________________________________
****************************************************************************
RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM PACKAGE
Reference: SAN DIEGO COUNTY FLOOD CONTROL DISTRICT
2003,1985,1981 HYDROLOGY MANUAL
(c) Copyright 1982-2014 Advanced Engineering Software (aes)
Ver. 21.0 Release Date: 06/01/2014 License ID 1459
Analysis prepared by:
BHA INC.
5115 AVENIDA ENCINAS, SUITE L
CARLSBAD, CA 92008
************************** DESCRIPTION OF STUDY **************************
* EXISTING 100 YEAR STORM HYDROLOGY *
* 786 PALM AVE *
* JN 1130-1501-600 *
**************************************************************************
FILE NAME: K:\HYDRO\1501\1501E103.DAT
TIME/DATE OF STUDY: 17:36 04/09/2022
----------------------------------------------------------------------------
USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION:
----------------------------------------------------------------------------
2003 SAN DIEGO MANUAL CRITERIA
USER SPECIFIED STORM EVENT(YEAR) = 100.00
6-HOUR DURATION PRECIPITATION (INCHES) = 2.660
SPECIFIED MINIMUM PIPE SIZE(INCH) = 3.00
SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE FOR FRICTION SLOPE = 0.95
SAN DIEGO HYDROLOGY MANUAL "C"-VALUES USED FOR RATIONAL METHOD
NOTE: USE MODIFIED RATIONAL METHOD PROCEDURES FOR CONFLUENCE ANALYSIS
*USER-DEFINED STREET-SECTIONS FOR COUPLED PIPEFLOW AND STREETFLOW MODEL*
HALF- CROWN TO STREET-CROSSFALL: CURB GUTTER-GEOMETRIES: MANNING
WIDTH CROSSFALL IN- / OUT-/PARK- HEIGHT WIDTH LIP HIKE FACTOR
NO. (FT) (FT) SIDE / SIDE/ WAY (FT) (FT) (FT) (FT) (n)
=== ===== ========= ================= ====== ===== ====== ===== =======
1 30.0 20.0 0.018/0.018/0.020 0.67 2.00 0.0313 0.167 0.0150
GLOBAL STREET FLOW-DEPTH CONSTRAINTS:
1. Relative Flow-Depth = 0.00 FEET
as (Maximum Allowable Street Flow Depth) - (Top-of-Curb)
2. (Depth)*(Velocity) Constraint = 6.0 (FT*FT/S)
*SIZE PIPE WITH A FLOW CAPACITY GREATER THAN
OR EQUAL TO THE UPSTREAM TRIBUTARY PIPE.*
****************************************************************************
FLOW PROCESS FROM NODE 10.00 TO NODE 20.00 IS CODE = 21
----------------------------------------------------------------------------
>>>>>RATIONAL METHOD INITIAL SUBAREA ANALYSIS<<<<<
============================================================================
*USER SPECIFIED(SUBAREA):
USER-SPECIFIED RUNOFF COEFFICIENT = .4600
S.C.S. CURVE NUMBER (AMC II) = 0
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INITIAL SUBAREA FLOW-LENGTH(FEET) = 100.00
UPSTREAM ELEVATION(FEET) = 58.24
DOWNSTREAM ELEVATION(FEET) = 57.50
ELEVATION DIFFERENCE(FEET) = 0.74
SUBAREA OVERLAND TIME OF FLOW(MIN.) = 9.832
WARNING: INITIAL SUBAREA FLOW PATH LENGTH IS GREATER THAN
THE MAXIMUM OVERLAND FLOW LENGTH = 59.60
(Reference: Table 3-1B of Hydrology Manual)
THE MAXIMUM OVERLAND FLOW LENGTH IS USED IN Tc CALCULATION!
100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 4.531
SUBAREA RUNOFF(CFS) = 0.13
TOTAL AREA(ACRES) = 0.06 TOTAL RUNOFF(CFS) = 0.13
****************************************************************************
FLOW PROCESS FROM NODE 20.00 TO NODE 30.00 IS CODE = 61
----------------------------------------------------------------------------
>>>>>COMPUTE STREET FLOW TRAVEL TIME THRU SUBAREA<<<<<
>>>>>(STANDARD CURB SECTION USED)<<<<<
============================================================================
UPSTREAM ELEVATION(FEET) = 57.50 DOWNSTREAM ELEVATION(FEET) = 54.80
STREET LENGTH(FEET) = 121.00 CURB HEIGHT(INCHES) = 6.0
STREET HALFWIDTH(FEET) = 24.00
DISTANCE FROM CROWN TO CROSSFALL GRADEBREAK(FEET) = 1.00
INSIDE STREET CROSSFALL(DECIMAL) = 0.020
OUTSIDE STREET CROSSFALL(DECIMAL) = 0.020
SPECIFIED NUMBER OF HALFSTREETS CARRYING RUNOFF = 1
STREET PARKWAY CROSSFALL(DECIMAL) = 0.020
Manning's FRICTION FACTOR for Streetflow Section(curb-to-curb) = 0.0130
Manning's FRICTION FACTOR for Back-of-Walk Flow Section = 0.0200
**TRAVEL TIME COMPUTED USING ESTIMATED FLOW(CFS) = 0.31
STREETFLOW MODEL RESULTS USING ESTIMATED FLOW:
STREET FLOW DEPTH(FEET) = 0.16
HALFSTREET FLOOD WIDTH(FEET) = 1.50
AVERAGE FLOW VELOCITY(FEET/SEC.) = 3.25
PRODUCT OF DEPTH&VELOCITY(FT*FT/SEC.) = 0.51
STREET FLOW TRAVEL TIME(MIN.) = 0.62 Tc(MIN.) = 10.45
100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 4.356
*USER SPECIFIED(SUBAREA):
USER-SPECIFIED RUNOFF COEFFICIENT = .4500
S.C.S. CURVE NUMBER (AMC II) = 0
AREA-AVERAGE RUNOFF COEFFICIENT = 0.452
SUBAREA AREA(ACRES) = 0.18 SUBAREA RUNOFF(CFS) = 0.36
TOTAL AREA(ACRES) = 0.2 PEAK FLOW RATE(CFS) = 0.48
END OF SUBAREA STREET FLOW HYDRAULICS:
DEPTH(FEET) = 0.17 HALFSTREET FLOOD WIDTH(FEET) = 2.21
FLOW VELOCITY(FEET/SEC.) = 2.89 DEPTH*VELOCITY(FT*FT/SEC.) = 0.49
LONGEST FLOWPATH FROM NODE 10.00 TO NODE 30.00 = 221.00 FEET.
============================================================================
END OF STUDY SUMMARY:
TOTAL AREA(ACRES) = 0.2 TC(MIN.) = 10.45
PEAK FLOW RATE(CFS) = 0.48
============================================================================
============================================================================
END OF RATIONAL METHOD ANALYSIS
786 Palm Avenue
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3.2 Developed Hydrology Calculations
100-Year Storm
____________________________________________________________________________
****************************************************************************
RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM PACKAGE
Reference: SAN DIEGO COUNTY FLOOD CONTROL DISTRICT
2003,1985,1981 HYDROLOGY MANUAL
(c) Copyright 1982-2014 Advanced Engineering Software (aes)
Ver. 21.0 Release Date: 06/01/2014 License ID 1459
Analysis prepared by:
BHA INC.
5115 AVENIDA ENCINAS, SUITE L
CARLSBAD, CA 92008
************************** DESCRIPTION OF STUDY **************************
* DEVELOPED 100 YEAR STORM HYDROLOGY *
* 786 PALM AVE *
* JN 1130-1501-600 *
**************************************************************************
FILE NAME: K:\HYDRO\1501\1501P103.DAT
TIME/DATE OF STUDY: 16:07 08/03/2022
----------------------------------------------------------------------------
USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION:
----------------------------------------------------------------------------
2003 SAN DIEGO MANUAL CRITERIA
USER SPECIFIED STORM EVENT(YEAR) = 100.00
6-HOUR DURATION PRECIPITATION (INCHES) = 2.660
SPECIFIED MINIMUM PIPE SIZE(INCH) = 3.00
SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE FOR FRICTION SLOPE = 0.95
SAN DIEGO HYDROLOGY MANUAL "C"-VALUES USED FOR RATIONAL METHOD
NOTE: USE MODIFIED RATIONAL METHOD PROCEDURES FOR CONFLUENCE ANALYSIS
*USER-DEFINED STREET-SECTIONS FOR COUPLED PIPEFLOW AND STREETFLOW MODEL*
HALF- CROWN TO STREET-CROSSFALL: CURB GUTTER-GEOMETRIES: MANNING
WIDTH CROSSFALL IN- / OUT-/PARK- HEIGHT WIDTH LIP HIKE FACTOR
NO. (FT) (FT) SIDE / SIDE/ WAY (FT) (FT) (FT) (FT) (n)
=== ===== ========= ================= ====== ===== ====== ===== =======
1 30.0 20.0 0.018/0.018/0.020 0.67 2.00 0.0313 0.167 0.0150
GLOBAL STREET FLOW-DEPTH CONSTRAINTS:
1. Relative Flow-Depth = 0.00 FEET
as (Maximum Allowable Street Flow Depth) - (Top-of-Curb)
2. (Depth)*(Velocity) Constraint = 6.0 (FT*FT/S)
*SIZE PIPE WITH A FLOW CAPACITY GREATER THAN
OR EQUAL TO THE UPSTREAM TRIBUTARY PIPE.*
****************************************************************************
FLOW PROCESS FROM NODE 10.00 TO NODE 20.00 IS CODE = 21
----------------------------------------------------------------------------
>>>>>RATIONAL METHOD INITIAL SUBAREA ANALYSIS<<<<<
============================================================================
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*USER SPECIFIED(SUBAREA):
USER-SPECIFIED RUNOFF COEFFICIENT = .4400
S.C.S. CURVE NUMBER (AMC II) = 0
INITIAL SUBAREA FLOW-LENGTH(FEET) = 100.00
UPSTREAM ELEVATION(FEET) = 58.24
DOWNSTREAM ELEVATION(FEET) = 57.50
ELEVATION DIFFERENCE(FEET) = 0.74
SUBAREA OVERLAND TIME OF FLOW(MIN.) = 10.140
WARNING: INITIAL SUBAREA FLOW PATH LENGTH IS GREATER THAN
THE MAXIMUM OVERLAND FLOW LENGTH = 59.60
(Reference: Table 3-1B of Hydrology Manual)
THE MAXIMUM OVERLAND FLOW LENGTH IS USED IN Tc CALCULATION!
100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 4.442
SUBAREA RUNOFF(CFS) = 0.11
TOTAL AREA(ACRES) = 0.06 TOTAL RUNOFF(CFS) = 0.11
****************************************************************************
FLOW PROCESS FROM NODE 20.00 TO NODE 40.00 IS CODE = 61
----------------------------------------------------------------------------
>>>>>COMPUTE STREET FLOW TRAVEL TIME THRU SUBAREA<<<<<
>>>>>(STANDARD CURB SECTION USED)<<<<<
============================================================================
UPSTREAM ELEVATION(FEET) = 57.50 DOWNSTREAM ELEVATION(FEET) = 56.77
STREET LENGTH(FEET) = 47.00 CURB HEIGHT(INCHES) = 6.0
STREET HALFWIDTH(FEET) = 24.00
DISTANCE FROM CROWN TO CROSSFALL GRADEBREAK(FEET) = 1.00
INSIDE STREET CROSSFALL(DECIMAL) = 0.020
OUTSIDE STREET CROSSFALL(DECIMAL) = 0.020
SPECIFIED NUMBER OF HALFSTREETS CARRYING RUNOFF = 1
STREET PARKWAY CROSSFALL(DECIMAL) = 0.020
Manning's FRICTION FACTOR for Streetflow Section(curb-to-curb) = 0.0130
Manning's FRICTION FACTOR for Back-of-Walk Flow Section = 0.0200
**TRAVEL TIME COMPUTED USING ESTIMATED FLOW(CFS) = 0.19
STREETFLOW MODEL RESULTS USING ESTIMATED FLOW:
STREET FLOW DEPTH(FEET) = 0.16
HALFSTREET FLOOD WIDTH(FEET) = 1.50
AVERAGE FLOW VELOCITY(FEET/SEC.) = 2.71
PRODUCT OF DEPTH&VELOCITY(FT*FT/SEC.) = 0.42
STREET FLOW TRAVEL TIME(MIN.) = 0.29 Tc(MIN.) = 10.43
100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 4.362
*USER SPECIFIED(SUBAREA):
USER-SPECIFIED RUNOFF COEFFICIENT = .6900
S.C.S. CURVE NUMBER (AMC II) = 0
AREA-AVERAGE RUNOFF COEFFICIENT = 0.554
SUBAREA AREA(ACRES) = 0.05 SUBAREA RUNOFF(CFS) = 0.15
TOTAL AREA(ACRES) = 0.1 PEAK FLOW RATE(CFS) = 0.26
END OF SUBAREA STREET FLOW HYDRAULICS:
DEPTH(FEET) = 0.16 HALFSTREET FLOOD WIDTH(FEET) = 1.50
FLOW VELOCITY(FEET/SEC.) = 2.71 DEPTH*VELOCITY(FT*FT/SEC.) = 0.42
LONGEST FLOWPATH FROM NODE 10.00 TO NODE 40.00 = 147.00 FEET.
****************************************************************************
FLOW PROCESS FROM NODE 40.00 TO NODE 40.00 IS CODE = 1
----------------------------------------------------------------------------
>>>>>DESIGNATE INDEPENDENT STREAM FOR CONFLUENCE<<<<<
============================================================================
TOTAL NUMBER OF STREAMS = 2
CONFLUENCE VALUES USED FOR INDEPENDENT STREAM 1 ARE:
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TIME OF CONCENTRATION(MIN.) = 10.43
RAINFALL INTENSITY(INCH/HR) = 4.36
TOTAL STREAM AREA(ACRES) = 0.11
PEAK FLOW RATE(CFS) AT CONFLUENCE = 0.26
****************************************************************************
FLOW PROCESS FROM NODE 30.00 TO NODE 40.00 IS CODE = 21
----------------------------------------------------------------------------
>>>>>RATIONAL METHOD INITIAL SUBAREA ANALYSIS<<<<<
============================================================================
*USER SPECIFIED(SUBAREA):
USER-SPECIFIED RUNOFF COEFFICIENT = .5200
S.C.S. CURVE NUMBER (AMC II) = 0
INITIAL SUBAREA FLOW-LENGTH(FEET) = 107.00
UPSTREAM ELEVATION(FEET) = 59.08
DOWNSTREAM ELEVATION(FEET) = 57.62
ELEVATION DIFFERENCE(FEET) = 1.46
SUBAREA OVERLAND TIME OF FLOW(MIN.) = 8.177
WARNING: INITIAL SUBAREA FLOW PATH LENGTH IS GREATER THAN
THE MAXIMUM OVERLAND FLOW LENGTH = 75.47
(Reference: Table 3-1B of Hydrology Manual)
THE MAXIMUM OVERLAND FLOW LENGTH IS USED IN Tc CALCULATION!
100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 5.103
SUBAREA RUNOFF(CFS) = 0.08
TOTAL AREA(ACRES) = 0.03 TOTAL RUNOFF(CFS) = 0.08
****************************************************************************
FLOW PROCESS FROM NODE 40.00 TO NODE 40.00 IS CODE = 1
----------------------------------------------------------------------------
>>>>>DESIGNATE INDEPENDENT STREAM FOR CONFLUENCE<<<<<
>>>>>AND COMPUTE VARIOUS CONFLUENCED STREAM VALUES<<<<<
============================================================================
TOTAL NUMBER OF STREAMS = 2
CONFLUENCE VALUES USED FOR INDEPENDENT STREAM 2 ARE:
TIME OF CONCENTRATION(MIN.) = 8.18
RAINFALL INTENSITY(INCH/HR) = 5.10
TOTAL STREAM AREA(ACRES) = 0.03
PEAK FLOW RATE(CFS) AT CONFLUENCE = 0.08
** CONFLUENCE DATA **
STREAM RUNOFF Tc INTENSITY AREA
NUMBER (CFS) (MIN.) (INCH/HOUR) (ACRE)
1 0.26 10.43 4.362 0.11
2 0.08 8.18 5.103 0.03
RAINFALL INTENSITY AND TIME OF CONCENTRATION RATIO
CONFLUENCE FORMULA USED FOR 2 STREAMS.
** PEAK FLOW RATE TABLE **
STREAM RUNOFF Tc INTENSITY
NUMBER (CFS) (MIN.) (INCH/HOUR)
1 0.29 8.18 5.103
2 0.33 10.43 4.362
COMPUTED CONFLUENCE ESTIMATES ARE AS FOLLOWS:
PEAK FLOW RATE(CFS) = 0.33 Tc(MIN.) = 10.43
TOTAL AREA(ACRES) = 0.1
LONGEST FLOWPATH FROM NODE 10.00 TO NODE 40.00 = 147.00 FEET.
****************************************************************************
FLOW PROCESS FROM NODE 40.00 TO NODE 50.00 IS CODE = 61
----------------------------------------------------------------------------
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>>>>>COMPUTE STREET FLOW TRAVEL TIME THRU SUBAREA<<<<<
>>>>>(STANDARD CURB SECTION USED)<<<<<
============================================================================
UPSTREAM ELEVATION(FEET) = 56.77 DOWNSTREAM ELEVATION(FEET) = 54.80
STREET LENGTH(FEET) = 74.00 CURB HEIGHT(INCHES) = 6.0
STREET HALFWIDTH(FEET) = 24.00
DISTANCE FROM CROWN TO CROSSFALL GRADEBREAK(FEET) = 1.50
INSIDE STREET CROSSFALL(DECIMAL) = 0.020
OUTSIDE STREET CROSSFALL(DECIMAL) = 0.020
SPECIFIED NUMBER OF HALFSTREETS CARRYING RUNOFF = 1
STREET PARKWAY CROSSFALL(DECIMAL) = 0.020
Manning's FRICTION FACTOR for Streetflow Section(curb-to-curb) = 0.0130
Manning's FRICTION FACTOR for Back-of-Walk Flow Section = 0.0200
**TRAVEL TIME COMPUTED USING ESTIMATED FLOW(CFS) = 0.41
STREETFLOW MODEL RESULTS USING ESTIMATED FLOW:
STREET FLOW DEPTH(FEET) = 0.16
HALFSTREET FLOOD WIDTH(FEET) = 1.50
AVERAGE FLOW VELOCITY(FEET/SEC.) = 3.55
PRODUCT OF DEPTH&VELOCITY(FT*FT/SEC.) = 0.55
STREET FLOW TRAVEL TIME(MIN.) = 0.35 Tc(MIN.) = 10.78
100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 4.271
*USER SPECIFIED(SUBAREA):
USER-SPECIFIED RUNOFF COEFFICIENT = .5100
S.C.S. CURVE NUMBER (AMC II) = 0
AREA-AVERAGE RUNOFF COEFFICIENT = 0.534
SUBAREA AREA(ACRES) = 0.07 SUBAREA RUNOFF(CFS) = 0.15
TOTAL AREA(ACRES) = 0.2 PEAK FLOW RATE(CFS) = 0.47
END OF SUBAREA STREET FLOW HYDRAULICS:
DEPTH(FEET) = 0.16 HALFSTREET FLOOD WIDTH(FEET) = 1.50
FLOW VELOCITY(FEET/SEC.) = 3.55 DEPTH*VELOCITY(FT*FT/SEC.) = 0.55
LONGEST FLOWPATH FROM NODE 10.00 TO NODE 50.00 = 221.00 FEET.
****************************************************************************
FLOW PROCESS FROM NODE 50.00 TO NODE 50.00 IS CODE = 1
----------------------------------------------------------------------------
>>>>>DESIGNATE INDEPENDENT STREAM FOR CONFLUENCE<<<<<
============================================================================
TOTAL NUMBER OF STREAMS = 2
CONFLUENCE VALUES USED FOR INDEPENDENT STREAM 1 ARE:
TIME OF CONCENTRATION(MIN.) = 10.78
RAINFALL INTENSITY(INCH/HR) = 4.27
TOTAL STREAM AREA(ACRES) = 0.21
PEAK FLOW RATE(CFS) AT CONFLUENCE = 0.47
****************************************************************************
FLOW PROCESS FROM NODE 60.00 TO NODE 70.00 IS CODE = 21
----------------------------------------------------------------------------
>>>>>RATIONAL METHOD INITIAL SUBAREA ANALYSIS<<<<<
============================================================================
*USER SPECIFIED(SUBAREA):
USER-SPECIFIED RUNOFF COEFFICIENT = .4800
S.C.S. CURVE NUMBER (AMC II) = 0
INITIAL SUBAREA FLOW-LENGTH(FEET) = 92.00
UPSTREAM ELEVATION(FEET) = 57.78
DOWNSTREAM ELEVATION(FEET) = 55.63
ELEVATION DIFFERENCE(FEET) = 2.15
SUBAREA OVERLAND TIME OF FLOW(MIN.) = 7.981
WARNING: INITIAL SUBAREA FLOW PATH LENGTH IS GREATER THAN
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THE MAXIMUM OVERLAND FLOW LENGTH = 90.05
(Reference: Table 3-1B of Hydrology Manual)
THE MAXIMUM OVERLAND FLOW LENGTH IS USED IN Tc CALCULATION!
100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 5.184
SUBAREA RUNOFF(CFS) = 0.09
TOTAL AREA(ACRES) = 0.04 TOTAL RUNOFF(CFS) = 0.09
****************************************************************************
FLOW PROCESS FROM NODE 70.00 TO NODE 70.00 IS CODE = 1
----------------------------------------------------------------------------
>>>>>DESIGNATE INDEPENDENT STREAM FOR CONFLUENCE<<<<<
>>>>>AND COMPUTE VARIOUS CONFLUENCED STREAM VALUES<<<<<
============================================================================
TOTAL NUMBER OF STREAMS = 2
CONFLUENCE VALUES USED FOR INDEPENDENT STREAM 2 ARE:
TIME OF CONCENTRATION(MIN.) = 7.98
RAINFALL INTENSITY(INCH/HR) = 5.18
TOTAL STREAM AREA(ACRES) = 0.04
PEAK FLOW RATE(CFS) AT CONFLUENCE = 0.09
** CONFLUENCE DATA **
STREAM RUNOFF Tc INTENSITY AREA
NUMBER (CFS) (MIN.) (INCH/HOUR) (ACRE)
1 0.47 10.78 4.271 0.21
2 0.09 7.98 5.184 0.04
RAINFALL INTENSITY AND TIME OF CONCENTRATION RATIO
CONFLUENCE FORMULA USED FOR 2 STREAMS.
** PEAK FLOW RATE TABLE **
STREAM RUNOFF Tc INTENSITY
NUMBER (CFS) (MIN.) (INCH/HOUR)
1 0.48 7.98 5.184
2 0.55 10.78 4.271
COMPUTED CONFLUENCE ESTIMATES ARE AS FOLLOWS:
PEAK FLOW RATE(CFS) = 0.55 Tc(MIN.) = 10.78
TOTAL AREA(ACRES) = 0.2
LONGEST FLOWPATH FROM NODE 10.00 TO NODE 70.00 = 221.00 FEET.
============================================================================
END OF STUDY SUMMARY:
TOTAL AREA(ACRES) = 0.2 TC(MIN.) = 10.78
PEAK FLOW RATE(CFS) = 0.55
============================================================================
============================================================================
END OF RATIONAL METHOD ANALYSIS
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3.3 Vegetated Swale Calculations
100-Year Storm
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APN
Flow Path
(node to
node)
Flow
(cfs)
Swale
Slope
(%)
Side
Slopes
(%)
Depth
(ft)
Width
(ft)
10 30 to 40 0.08 1 2 0.06 5.53
10 30 to 40 0.08 1 5 0.07 2.98
10 30 to 40 0.08 2 2 0.05 4.77
10 30 to 40 0.08 2 5 0.07 2.67
11 60 TO 70 0.09 2 2 0.05 4.77
11 60 TO 70 0.09 2 5 0.07 2.82
See vegetated swale calculations in Chapter 3 of this report
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____________________________________________________________________________
****************************************************************************
HYDRAULIC ELEMENTS - I PROGRAM PACKAGE
(C) Copyright 1982-2014 Advanced Engineering Software (aes)
Ver. 21.0 Release Date: 06/01/2014 License ID 1459
Analysis prepared by:
BHA INC.
5115 AVENIDA ENCINAS, SUITE L
CARLSBAD, CA 92008
----------------------------------------------------------------------------
TIME/DATE OF STUDY: 16:23 08/03/2022
============================================================================
Problem Descriptions:
NODE 30 TO 40
VEGETATED SWALE AT 1% LONGITUDE AND 2% SIDE SLOPES
****************************************************************************
>>>>CHANNEL INPUT INFORMATION<<<<
----------------------------------------------------------------------------
CHANNEL Z1(HORIZONTAL/VERTICAL) = 50.00
Z2(HORIZONTAL/VERTICAL) = 50.00
BASEWIDTH(FEET) = 0.00
CONSTANT CHANNEL SLOPE(FEET/FEET) = 0.010000
UNIFORM FLOW(CFS) = 0.08
MANNINGS FRICTION FACTOR = 0.0240
============================================================================
NORMAL-DEPTH FLOW INFORMATION:
----------------------------------------------------------------------------
>>>>> NORMAL DEPTH(FEET) = 0.06
FLOW TOP-WIDTH(FEET) = 5.53
FLOW AREA(SQUARE FEET) = 0.15
HYDRAULIC DEPTH(FEET) = 0.03
FLOW AVERAGE VELOCITY(FEET/SEC.) = 0.52
UNIFORM FROUDE NUMBER = 0.554
PRESSURE + MOMENTUM(POUNDS) = 0.26
AVERAGED VELOCITY HEAD(FEET) = 0.004
SPECIFIC ENERGY(FEET) = 0.060
============================================================================
CRITICAL-DEPTH FLOW INFORMATION:
----------------------------------------------------------------------------
CRITICAL FLOW TOP-WIDTH(FEET) = 4.41
CRITICAL FLOW AREA(SQUARE FEET) = 0.10
CRITICAL FLOW HYDRAULIC DEPTH(FEET) = 0.02
CRITICAL FLOW AVERAGE VELOCITY(FEET/SEC.) = 0.82
CRITICAL DEPTH(FEET) = 0.04
CRITICAL FLOW PRESSURE + MOMENTUM(POUNDS) = 0.22
AVERAGED CRITICAL FLOW VELOCITY HEAD(FEET) = 0.011
CRITICAL FLOW SPECIFIC ENERGY(FEET) = 0.055
============================================================================
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____________________________________________________________________________
****************************************************************************
HYDRAULIC ELEMENTS - I PROGRAM PACKAGE
(C) Copyright 1982-2014 Advanced Engineering Software (aes)
Ver. 21.0 Release Date: 06/01/2014 License ID 1459
Analysis prepared by:
BHA INC.
5115 AVENIDA ENCINAS, SUITE L
CARLSBAD, CA 92008
----------------------------------------------------------------------------
TIME/DATE OF STUDY: 16:25 08/03/2022
============================================================================
Problem Descriptions:
NODE 30 TO 40
VEGETATED SWALE AT 1% LONGITUDE AND 5% SIDE SLOPES
****************************************************************************
>>>>CHANNEL INPUT INFORMATION<<<<
----------------------------------------------------------------------------
CHANNEL Z1(HORIZONTAL/VERTICAL) = 20.00
Z2(HORIZONTAL/VERTICAL) = 20.00
BASEWIDTH(FEET) = 0.00
CONSTANT CHANNEL SLOPE(FEET/FEET) = 0.010000
UNIFORM FLOW(CFS) = 0.08
MANNINGS FRICTION FACTOR = 0.0240
============================================================================
NORMAL-DEPTH FLOW INFORMATION:
----------------------------------------------------------------------------
>>>>> NORMAL DEPTH(FEET) = 0.07
FLOW TOP-WIDTH(FEET) = 2.98
FLOW AREA(SQUARE FEET) = 0.11
HYDRAULIC DEPTH(FEET) = 0.04
FLOW AVERAGE VELOCITY(FEET/SEC.) = 0.72
UNIFORM FROUDE NUMBER = 0.661
PRESSURE + MOMENTUM(POUNDS) = 0.28
AVERAGED VELOCITY HEAD(FEET) = 0.008
SPECIFIC ENERGY(FEET) = 0.082
============================================================================
CRITICAL-DEPTH FLOW INFORMATION:
----------------------------------------------------------------------------
CRITICAL FLOW TOP-WIDTH(FEET) = 2.53
CRITICAL FLOW AREA(SQUARE FEET) = 0.08
CRITICAL FLOW HYDRAULIC DEPTH(FEET) = 0.03
CRITICAL FLOW AVERAGE VELOCITY(FEET/SEC.) = 1.00
CRITICAL DEPTH(FEET) = 0.06
CRITICAL FLOW PRESSURE + MOMENTUM(POUNDS) = 0.26
AVERAGED CRITICAL FLOW VELOCITY HEAD(FEET) = 0.016
CRITICAL FLOW SPECIFIC ENERGY(FEET) = 0.079
============================================================================
786 Palm Avenue
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____________________________________________________________________________
****************************************************************************
HYDRAULIC ELEMENTS - I PROGRAM PACKAGE
(C) Copyright 1982-2014 Advanced Engineering Software (aes)
Ver. 21.0 Release Date: 06/01/2014 License ID 1459
Analysis prepared by:
BHA INC.
5115 AVENIDA ENCINAS, SUITE L
CARLSBAD, CA 92008
----------------------------------------------------------------------------
TIME/DATE OF STUDY: 16:26 08/03/2022
============================================================================
Problem Descriptions:
NODE 30 TO 40
VEGETATED SWALE AT 2% LONGITUDE AND 2% SIDE SLOPES
****************************************************************************
>>>>CHANNEL INPUT INFORMATION<<<<
----------------------------------------------------------------------------
CHANNEL Z1(HORIZONTAL/VERTICAL) = 50.00
Z2(HORIZONTAL/VERTICAL) = 50.00
BASEWIDTH(FEET) = 0.00
CONSTANT CHANNEL SLOPE(FEET/FEET) = 0.020000
UNIFORM FLOW(CFS) = 0.08
MANNINGS FRICTION FACTOR = 0.0240
============================================================================
NORMAL-DEPTH FLOW INFORMATION:
----------------------------------------------------------------------------
>>>>> NORMAL DEPTH(FEET) = 0.05
FLOW TOP-WIDTH(FEET) = 4.77
FLOW AREA(SQUARE FEET) = 0.11
HYDRAULIC DEPTH(FEET) = 0.02
FLOW AVERAGE VELOCITY(FEET/SEC.) = 0.70
UNIFORM FROUDE NUMBER = 0.803
PRESSURE + MOMENTUM(POUNDS) = 0.22
AVERAGED VELOCITY HEAD(FEET) = 0.008
SPECIFIC ENERGY(FEET) = 0.055
============================================================================
CRITICAL-DEPTH FLOW INFORMATION:
----------------------------------------------------------------------------
CRITICAL FLOW TOP-WIDTH(FEET) = 4.41
CRITICAL FLOW AREA(SQUARE FEET) = 0.10
CRITICAL FLOW HYDRAULIC DEPTH(FEET) = 0.02
CRITICAL FLOW AVERAGE VELOCITY(FEET/SEC.) = 0.82
CRITICAL DEPTH(FEET) = 0.04
CRITICAL FLOW PRESSURE + MOMENTUM(POUNDS) = 0.22
AVERAGED CRITICAL FLOW VELOCITY HEAD(FEET) = 0.011
CRITICAL FLOW SPECIFIC ENERGY(FEET) = 0.055
============================================================================
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___________________________________________________________________________
****************************************************************************
HYDRAULIC ELEMENTS - I PROGRAM PACKAGE
(C) Copyright 1982-2014 Advanced Engineering Software (aes)
Ver. 21.0 Release Date: 06/01/2014 License ID 1459
Analysis prepared by:
____________________________________________________________________________
****************************************************************************
HYDRAULIC ELEMENTS - I PROGRAM PACKAGE
(C) Copyright 1982-2014 Advanced Engineering Software (aes)
Ver. 21.0 Release Date: 06/01/2014 License ID 1459
Analysis prepared by:
BHA INC.
5115 AVENIDA ENCINAS, SUITE L
CARLSBAD, CA 92008
----------------------------------------------------------------------------
TIME/DATE OF STUDY: 16:28 08/03/2022
============================================================================
Problem Descriptions:
NODE 30 TO 40
VEGETATED SWALE AT 2% LONGITUDE AND 5% SIDE SLOPES
****************************************************************************
>>>>CHANNEL INPUT INFORMATION<<<<
----------------------------------------------------------------------------
CHANNEL Z1(HORIZONTAL/VERTICAL) = 20.00
Z2(HORIZONTAL/VERTICAL) = 20.00
BASEWIDTH(FEET) = 0.00
CONSTANT CHANNEL SLOPE(FEET/FEET) = 0.020000
UNIFORM FLOW(CFS) = 0.08
MANNINGS FRICTION FACTOR = 0.0240
============================================================================
NORMAL-DEPTH FLOW INFORMATION:
----------------------------------------------------------------------------
>>>>> NORMAL DEPTH(FEET) = 0.07
FLOW TOP-WIDTH(FEET) = 2.67
FLOW AREA(SQUARE FEET) = 0.09
HYDRAULIC DEPTH(FEET) = 0.03
FLOW AVERAGE VELOCITY(FEET/SEC.) = 0.90
UNIFORM FROUDE NUMBER = 0.866
PRESSURE + MOMENTUM(POUNDS) = 0.26
AVERAGED VELOCITY HEAD(FEET) = 0.013
SPECIFIC ENERGY(FEET) = 0.079
============================================================================
CRITICAL-DEPTH FLOW INFORMATION:
----------------------------------------------------------------------------
CRITICAL FLOW TOP-WIDTH(FEET) = 2.53
CRITICAL FLOW AREA(SQUARE FEET) = 0.08
CRITICAL FLOW HYDRAULIC DEPTH(FEET) = 0.03
CRITICAL FLOW AVERAGE VELOCITY(FEET/SEC.) = 1.00
CRITICAL DEPTH(FEET) = 0.06
CRITICAL FLOW PRESSURE + MOMENTUM(POUNDS) = 0.26
AVERAGED CRITICAL FLOW VELOCITY HEAD(FEET) = 0.016
CRITICAL FLOW SPECIFIC ENERGY(FEET) = 0.079
============================================================================
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____________________________________________________________________________
****************************************************************************
HYDRAULIC ELEMENTS - I PROGRAM PACKAGE
(C) Copyright 1982-2014 Advanced Engineering Software (aes)
Ver. 21.0 Release Date: 06/01/2014 License ID 1459
Analysis prepared by:
BHA INC.
5115 AVENIDA ENCINAS, SUITE L
CARLSBAD, CA 92008
----------------------------------------------------------------------------
TIME/DATE OF STUDY: 16:39 08/03/2022
============================================================================
Problem Descriptions:
NODE 60 TO 70
VEGETATED SWALE AT 2% LONGITUDE AND 2% SIDE SLOPES
****************************************************************************
>>>>CHANNEL INPUT INFORMATION<<<<
----------------------------------------------------------------------------
CHANNEL Z1(HORIZONTAL/VERTICAL) = 50.00
Z2(HORIZONTAL/VERTICAL) = 50.00
BASEWIDTH(FEET) = 0.00
CONSTANT CHANNEL SLOPE(FEET/FEET) = 0.020000
UNIFORM FLOW(CFS) = 0.09
MANNINGS FRICTION FACTOR = 0.0240
============================================================================
NORMAL-DEPTH FLOW INFORMATION:
----------------------------------------------------------------------------
>>>>> NORMAL DEPTH(FEET) = 0.05
FLOW TOP-WIDTH(FEET) = 4.77
FLOW AREA(SQUARE FEET) = 0.11
HYDRAULIC DEPTH(FEET) = 0.02
FLOW AVERAGE VELOCITY(FEET/SEC.) = 0.79
UNIFORM FROUDE NUMBER = 0.903
PRESSURE + MOMENTUM(POUNDS) = 0.25
AVERAGED VELOCITY HEAD(FEET) = 0.010
SPECIFIC ENERGY(FEET) = 0.057
============================================================================
CRITICAL-DEPTH FLOW INFORMATION:
----------------------------------------------------------------------------
CRITICAL FLOW TOP-WIDTH(FEET) = 4.65
CRITICAL FLOW AREA(SQUARE FEET) = 0.11
CRITICAL FLOW HYDRAULIC DEPTH(FEET) = 0.02
CRITICAL FLOW AVERAGE VELOCITY(FEET/SEC.) = 0.83
CRITICAL DEPTH(FEET) = 0.05
CRITICAL FLOW PRESSURE + MOMENTUM(POUNDS) = 0.25
AVERAGED CRITICAL FLOW VELOCITY HEAD(FEET) = 0.011
CRITICAL FLOW SPECIFIC ENERGY(FEET) = 0.057
============================================================================
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____________________________________________________________________________
****************************************************************************
HYDRAULIC ELEMENTS - I PROGRAM PACKAGE
(C) Copyright 1982-2014 Advanced Engineering Software (aes)
Ver. 21.0 Release Date: 06/01/2014 License ID 1459
Analysis prepared by:
BHA INC.
5115 AVENIDA ENCINAS, SUITE L
CARLSBAD, CA 92008
----------------------------------------------------------------------------
TIME/DATE OF STUDY: 16:41 08/03/2022
============================================================================
Problem Descriptions:
NODE 60 TO 70
VEGETATED SWALE AT 2% LONGITUDE AND 5% SIDE SLOPES
****************************************************************************
>>>>CHANNEL INPUT INFORMATION<<<<
----------------------------------------------------------------------------
CHANNEL Z1(HORIZONTAL/VERTICAL) = 20.00
Z2(HORIZONTAL/VERTICAL) = 20.00
BASEWIDTH(FEET) = 0.00
CONSTANT CHANNEL SLOPE(FEET/FEET) = 0.020000
UNIFORM FLOW(CFS) = 0.09
MANNINGS FRICTION FACTOR = 0.0240
============================================================================
NORMAL-DEPTH FLOW INFORMATION:
----------------------------------------------------------------------------
>>>>> NORMAL DEPTH(FEET) = 0.07
FLOW TOP-WIDTH(FEET) = 2.82
FLOW AREA(SQUARE FEET) = 0.10
HYDRAULIC DEPTH(FEET) = 0.04
FLOW AVERAGE VELOCITY(FEET/SEC.) = 0.90
UNIFORM FROUDE NUMBER = 0.848
PRESSURE + MOMENTUM(POUNDS) = 0.30
AVERAGED VELOCITY HEAD(FEET) = 0.013
SPECIFIC ENERGY(FEET) = 0.083
============================================================================
CRITICAL-DEPTH FLOW INFORMATION:
----------------------------------------------------------------------------
CRITICAL FLOW TOP-WIDTH(FEET) = 2.62
CRITICAL FLOW AREA(SQUARE FEET) = 0.09
CRITICAL FLOW HYDRAULIC DEPTH(FEET) = 0.03
CRITICAL FLOW AVERAGE VELOCITY(FEET/SEC.) = 1.05
CRITICAL DEPTH(FEET) = 0.07
CRITICAL FLOW PRESSURE + MOMENTUM(POUNDS) = 0.30
AVERAGED CRITICAL FLOW VELOCITY HEAD(FEET) = 0.017
CRITICAL FLOW SPECIFIC ENERGY(FEET) = 0.083
============================================================================
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3.4 Volumetric and Flow Calculations for Attenuation of
Developed Runoff
100-Year Storm
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Volumetric and flow Calculations for Attenuation of Developed Runoff
Calculations for Total Infiltration from Permeable Pavers and Bioretention Basin
Total Permeable Paver Area = 1,561 sf
Total Bioretention Area = 25 sf
Total = 1,586 sf
Calculate Total Infiltration in cfs Based on 1,586 sf
Site is Type "B" Soils, Assume Infiltration Rate I = 0.2 in/hr
QINF = I x Area = 1,586 sf * 0.2 in/hr =0.01 cfs
Calculations for Total Volume of Storage Availbale from Permeable Pavers and Bioretention Basin
Total Permeable Paver Area = 1,561 sf Depth of Gravel Section Underneath Permeble Pavers = 6 in = 0.5 ft
Total Bioretnetion Area = 25 sf Depth of Gravel Section Underneath Bioretnetion Basin = 18 in = 1.5 ft
Total = 1,586 sf
Total Storage Volume Available in Gravel Section Underneath Permeble Pavers1 = 312 cf
Total Storage Volume Available in Gravel Section Underneath Bioretnetion Basin1 = 15 cf
Total = 327 cf
Notes
1 - Assume a 40% Pososity in Gravel Section
Calculate Total Flow Generated from Permeable Pavers assuming Tc = 5 minutes, Intensiy = 7.01 in/hr
Q = CIA, C=0.25, I=7.01 in/hr, Area = 1,561 sf
Q = 0.06 cfs
Calculate Total Volume Stored in Gravel Section Underneath Permeable Pavers
Vol = Q * Time, Assume 5 min Tc
Vol = 18 cf < 312 cf
Calculate Total Volume Stored in Garvel Section Underneath Permeable Pavers (Node 70)
Assume Q = 0.09 cfs
Vol = Q * Time, Assume 5 min Tc
Vol = 27 cf >15 cf
Asume Q = 0.045 cfs
Vol = 14 cf <15 cf
Approximate Flow Attenuation
Infiltration from Permeable Pavers and Bioretention Basin = 0.01 cfs
Flow Stored in Gravel Section Underneath Permeable Pavers = 0.06 cfs
Flow Stored in Gravel Section Underneath Bioretention Basin (say) = 0.01 cfs
Total Flow Reduction = 0.08 cfs
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Chapter 4
References
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4.1 Methodology – Rational Method Peak Flow Determination
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