HomeMy WebLinkAboutAMEND 2024-0008; INNS OF AMERICA; PRELIMINARY DRAINAGE STUDY; 2025-05-08Jo
PRELIMINARY DRAINAGE STUDY
CARLSBAD COMMONS
5010 AVENIDA ENCINAS
(INNS OF AMERICA)
APN:
210-090-52
50 IO A venida Encinas
Carlsbad, CA 92008
Prepared By:
RCE 80667
Van Ryn Engineering, Inc.
16766 Bernardo Center Dr., Ste 115
San Diego, CA 92128
"~ VA N RVN
Prepared for:
Alliance Development Services
17828 Villamoura Dr.,
Poway, CA 92064
/
May 8, 2025
EXP: 3-31-27
CITY OF CARLSBAD
MAY 2 2 2025
PLANNING DIVISION
DRAINAGE STUDY -5010 AVENJDA ENCINAS SPETEMBER 2024
TABLE OF CONTENTS
1. INTRODUCTION .................................................................................................................................. 4
1.1 Exi sting Conditions ......................................................................................................................... 4
1.2 Proposed Conditions ...................................................................................................................... 4
2. METHODOLOGY .................................................................................................................................. 5
2.1 Rationa l Method ............................................................................................................................. 5
2.2 Runoff Coefficient ........................................................................................................................... 5
2.3 Rainfall Intensity .............................................................................................................................. 5
2.4 Tributary Areas ............................................................................................................................... 5
3. CALCULATIONS/RESULTS ................................................................................................................... 6
3.1 Pre & Post-Development Peak Flow Comparison ....................................................................... 6
3.2 Storm Water Volume Calcu lations ................................................................................................ 8
4. CONCLUSION ...................................................................................................................................... 9
Appendix 1 ....................................................... Pre & Post Project Hydrology Calculations
Appendix 2 .......................................................... Existing and Proposed Drainage Exhibits
DRAINAGE STUDY-50I 0AVENIDA ENCINAS SPETEMBER 2024
Figure 1 Vicinity Map
VICINITY MAP
N. T.S.
DRAINAGE STUDY -5 OJ O A VENJDA ENCJNAS SPETEMBER 2024
1. INTRODUCTION
1.1 Existing Conditions
The project site is located at 5010 Avenida Encinas in Carlsbad, California. The lot is 117,738 square
feet, or 2. 703 acres and consists of the existing hotel, parking areas, and landscape areas. The focus of
this drainage study is the northern portion of the site along Cannon Road. This portion of the site exists
as primarily pervious landscape area, except for the existing utility enclosure and concrete wall. This
northern portion of the site is the only area where improvements are to be made, and the rest of the lot
will remain unchanged. The drainage basin that is the focus of this study has a total area of 7,782
square feet, or 0.179 acres, and consists of 685 square feet of impervious surfaces. The area is made
up of 8.80% impervious surfaces.
1.2 Proposed Conditions
The project proposes the construction of a new recreational space on the northern portion of the lot. The
proposed hardscape consists of two concrete pickle ball courts, along with a room for bike and surfboard
storage. The existing utility enclosure will remain undisturbed, but portions of the concrete wall will be
removed to accommodate the proposed hardscape. The proposed conditions introduce 4,821 square feet
of new/replaced impervious area, resulting in the percentage of impervious surfaces increasing to 67.55%.
To account for the increase in impervious areas, a bioretention basin is proposed on the western side of
the proposed hardscape. Runoff-from the new pickleball courts will be collected in a landscape drain
which discharges directly into the proposed basin.
DRAINAGE STUDY-5010AVENIDA ENCINAS SPETEMBER 2024
2. METHODOLOGY
The proposed project has been analyzed to determine the peak runoff flow for the 100-year, 6-hour rainfall
event using the Rational Method per the San Diego County Hydrology Manual. The Weighted Runoff
Coefficient, C, for the existing and proposed conditions was calculated using section 3 .1.2 of the San Diego
County Hydrology Manual. A rainfall intensity value was found using the equation located in Figure 3-1
of the manual. The rainfaJI intensity for the existing and proposed drainage areas was calculated using a
minimum time of concentration of 5 min. Based on the 100-year, 6-hour conditions, the intensity was found
to be 6.59 inches per hour. The County of San Diego Hydrology Manual Rainfall Isopluvials were used to
find a precipitation value of 2.5 inches resulting from A 100-year, 6-hour rainfall event. Civil 3D
Hydrographs were used to model the watershed, and correctly size the proposed bioretention basin to
account for the increase in peak runoff resulting from the proposed conditions.
2.1 Rational Method
As mentioned above, runoff from the project site was calculated for the 100-year storm events. Runoff was
calculated using the Rational Method which is given by the following equation:
Q =CxlxA
Where:
Q = Flow rate in cubic feet per second ( cfs)
C = Runoff coefficient
I = Rainfall Intensity in inches per hour (in/hr)
A = Drainage basin area in acres, (ac)
Rational Method calculations were performed using the San Diego County Hydrology Manual
2.2 Runoff Coefficient
The runoff coefficients for the project were calcul ated using section 3.1.2 of the San Diego County
Hydrology Manual and using a weighted average runoff coefficient based on the actual and proposed
impervious areas.
2.3 Rainfall Intensity
Rainfall intensity was determined using Figure 3-1 of the San Diego County Hydrology Manual. Based on
a 5 min time of concentration for the existing and proposed conditions and an intensity of 6.59 inches per
hour has been calculated.
2.4 Tributary Areas
Drainage basins are delineated in the Post-Project Hydrology Exhibit in Appendix 2 and graphically portray
the tributary area for each drainage basin.
DRAINAGE STUDY-5010 AVENIDA ENCINAS SPETEMBER 2024
3. CALCULATIONS/RESULTS
3.1 Pre & Post-Development Peak Flow Comparison
3.1.1 Pre-Development Peak Flow
Precipitation 1ooyr,6hr = 2.5 (See Appendix 1 for County of San Diego Rainfall Isopluvial Map)
Weighted Runoff Coefficient "C" = (7,079 sf)(O.35) + (685 sf)(.9O) = 0.40
7,782 sf
Time of Concentration "Tc"= 5 min.
Intensity "i" = 7.44P6o-0645 = 7.44(2.5)(5-·0645) = 6.59 in/hr
Q=C*i* A= 0.40*6.59 in/hr*O.179 ac = 0.47 CFS
3.1.2 Post-Development Peak Flow
➔ D = 5 min., for minimum Tc
Weighted Runoff Coefficient "C" = (2,525 sf)(O.35) + (5 ,25 7 sf)(.9O) = 0.72
7,782 sf
Time of Concentration "Tc" = 5 min.
Intensity "i" = 7.44P6o-0•645 = 7.44(2.5)(5-·0645) = 6.59 in/hr
Q=C*i* A= 0.72*6.59 in/hr*O.179 ac = 0.85 CFS
➔ D = 5 min., for minimum Tc
DRAINAGE STUDY-5010 AVENIDA ENCINAS SPETEMBER 2024
Below are a series of tables which summarize the calculations provided.
' SITE IMPERVIOUS AREA COMPOSITION
TOTAL TOTAL TOTAL WEIGHTED
IMPERVIOUS PERVIOUS % PROJECT RUNOFF IMPERVIOUS AREA AREA AREA COEFFICIENT
(SQ-FT) (SQ-FT) SURFACES "C" (SQ-FT)
Existing 685 7,079 7,782 8.80% 0.40 Conditions
Proposed 5,257 2,525 7,782 67.55% 0.72 Conditions
Table 1. Runoff Coefficient "C" Comparison
The table above shows the difference in the weighted runoff coefficient, "C", between the existing and
proposed condition. Calculations of the weighted runoff coefficients are based on Section 3 .1.2 of the San
Diego County Hydrology Manual and underlying hydro logic soil group B.
EXISTING DRAINAGE FLOWS
WEIGHTED DRAINA DRAINAGE RUNOFF Q100 I 100 GE AREA AREA COEFFICIENT (CFS) (IN /HR) (SQ-FT) (C)
SITE 7,782 0.40 0.47 6.59
Table 2. Existing Condition Peak Drainage Flow Rates
Table 2 above lists the peak flow rates for the project site in the existing condition for the respective rainfall
events.
PROPOSED DRAINAGE FLOWS
DRAINAGE RUNOFF DRAINAGE Q1 00 I 100 AREA COEFFICIENT AREA (CFS) (IN/HR) (SQ-FT) (C)
SITE
7,782 0.72 0.85 6.59
Table 3. Proposed Condition Peak Drainage Flow Rates
Table 3 above lists the peak flow rates for the project site for the proposed condition for the respective
rainfall events.
DRAINAGE STUDY -5010 AVENIDA ENCINAS SPETEMBER 2024
PEAK FLOW COMPARISON
---------------------------
DRAINAGE Ql00
CONDITION AREA UNDETAINED Vl00
(SQ-FT) (CFS) (CU -FT)
EXISTING 7,782 0.47 650
PROPOSED 7,782 0.85 1,170
Table 4. Proposed Condition Peak Drainage Flow Rates
Table 4 above shows a comparison between the peak flow rates and precipitation volume for the proposed
condition and the existing condition.
3.2 Storm Water Volume Calculations
3.2.1 Pre-Development Volum e
Vol=C*P6*A
Vol=0.40*2.5 in*0.179 ac*3,630 = 650 cu-ft
3.2.2 Post-Development Volume
Vol=C*P6*A
Vol=0.72*2.5 in*0.179 ac*3,630 = 1,170 cu-ft
Li Vol= Post-Development Volume -Pre-Developement Vo lume
Li Vol= 1,170 cu-ft -650 cu-ft= 520 cu-ft
Because the proposed site improvements lead to an increase in peak runoff, a bioretention basin was
designed and sized to slow the peak runoff, and additional runoff volume. AutoCad Hydroghaphs was used
to calculate the peak runoff after the bioretention basin was implemented. See Appendix 1 for the
Hydraflow Hydrographs summary.
3.2.3 Proposed Basin Volumes
PR-DETENTION BASIN:
The proposed basin has 12.6 inches or 1.05 feet of freeboard above the top of grate elecation of 44.5 feet.
There is 6" or 0.5 feet of ponding below the top of grate elevation, meaning the basin has a combined depth
of 18.6 inches or 1.55 feet. The basin has a storage volume equal to 300 cubic ft. The basin will have a 12"
x 12" box inlet approximately 6" above the bottom elevation with 2 -4" orifice cut outs at the dirt elevatoin.
The riser structure will connect to an existing storm drain curb inlet box with a 12" pipe. According to
Hydraflow Hydrographs, the basin will be able to slow the peak runoff leaving the site from 0.86 CFS to
0.457 CFS. This is a smaller peak runoff value than the exisitng site value equal to 0.47 CFS. To verify
DRAINAGE STUDY-50I0AVENIDA ENCINAS SPETEMBER 2024
that ponding during a 100 year, 6 hour storm event will not exceed 36 hours a calculation was done based
off of the soil type on site. According to NRCS Soil Survey Maps, the soil on the site is type "B", which
corresponds to an infiltration rate of approximately 0.200 inches per hour. Given that the basin in question
has 6 inches of ponding, this means it will take approximately 30 hours for the basin to drawdown
completely. Precise infiltration tests will determine more accurate drawdown times during review of the
construciton plans.
(6 in)/ (0.2 in/lhr) = 30 hours.
Since the calculated vaue of30 hours is less than the ellowed limit of36 hours, the proposed basin complies
with the City of Carlsbad's standards.
4. CONCLUSION
As discussed previously the proposed project's peak runoff flow and volume will be mitigated using the
proposed bioretention basin. Therefore, the project will not negatively affect the downstream facilities or
adjacent properties. It is my professional opinion that the storm drain system as proposed in this report and
on the grading plans herein is adequate to intercept, contain and convey QIO0 and will not create negative
impacts to the downstream system from the velocity, volume, or surface flows.
DRAINAGE STUDY-5010 AVENJDA ENCINAS
APPENDIX 1
EXISTING & PROPOSED
HYDROLOGY CALCULATIONS
SPETEMBER 2024
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Rainfall Isopluvials
100 Year Rainfall Event -6 Hours
lsopluvial (inches)
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OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
Copyright SanGIS. Al Rights Reserved.
This products may contain information from the SANOAG Regional
Information System which cannot be reproduced without the
written permission of SANOAG.
This product may contain information which has been reproduced with
permission granted by Thomas Brothers Maps.
3 Miles
5010 AVENIDA ENCINAS
J-2439
S/8/202S
Drainage
Area Area Description
ON-SITE EX.
EX-1 DRAINAGE AREA
TOTAL:
8MP
location Basin Description
PR-1 Bioretention Basin
TOTAL
Note:
100 Yr Storm at 5 Min TC
Total
Area
(Ac)
0.18
0.18
Total
Area
(Ac)
0.18
0.18
Intensity: 6.59 in/hr
~_P_re_c~ip_:~ __ 2_.5_0 __ ~in
DETENTION BASIN SIZING
EX. PEAK RUNOFF VOLUME:
PR. PEAK RUNOFF VOLUME:
DELTA PRE VS. POST:
10.0
0.0
8.0
7.0
0.0
5.0
~
~
~
~
~"'!,,.
~ 7
~ 1'
I',
-~ ......
I
I
I
HYDROLOGY SUMMARY
PRE-PROJECT HYDOLOGY
Total Weighted
Total Area Impervious " " Runoff Intensity Peak Runoff Q:
(sq-ft) Area (Sq-Ft) Impervious Pervlous Coefficient (In/hr) (CFS)
7782 685 9% 91% 0.40 6.59 0.47
7782 685
POST-PROJECT HYDOLOGY
Total
Impervious Wei1hted Peak Runoff Q
Total Area Area " " Runoff Intensity Un-Detained:
(sq-ft) (Sq-Ftl Impervious Pervlous Coefficient (in/hr) (CFS)
7782 5257 68% 32% 0.72 6.59 0.86
7782 5257 68% 32% 0.72 6.S9 0.86
Runoff Coefficient
Impervious 0.90
Landscape 0.35
TOTAL LID PLANTER STORAGE CURVE
DEPTH ELEVATI AREA STAGE TOTAL
646 cu-ft 0 44 196.6 0 0
1170 cu-ft 0.25 44.25 245.3 61.325 61.325
0.5 44.5 297.5 74.375 135.7
524 cu-ft 0.75 44.75 353.3 88.325 224.025
1 45 412.54 103.135 327.16
11 1 1 11111 1111111111
1 11 111 1111111111
111)11 111)111111
' I EQUATION
' I = 7.44 P5 o-0.64S
=
4.0
i',~~ ',, I lntensily (in/hr) ... P5 • 6-Hour Precipitation (In)
3.0
20
I i 1.0
f0.o j°·a
.50.7
0.6
0.5
0.4
0.3
0.2
0.1
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15 20 30 40 50 1 Minutes Duration
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5.0 [
,.5 a
4.0 = 3.S-
3.0
2.5
2.0
1.5
1.0
lntenslty-Ouratlon DNJgn Chart • Template
Peak Runoff
Volume:
(cu-ft)
646
Peak
Peak Runoff Q Runoff
Detained: Volume:
(CFS) (cu-ft)
0.54 1170
0.54 1170
Dtrectlona for AppH-n:
(1) From precipitation maps determine 6 hr and 24 hr amounls
ror lhe seleded lrequency. These maps are included in lhe
Counly Hydrology Marual (10, 50, and 100 yr maps included
in the De&ign and Procedure Manual).
(2) Adjusl 6 hr pnidpitation (II necessary) so that It Is within
lhe range of 45% to 65% of lhe 24 hr precipitation (not
applicaple lo Desert).
(3) Plol 6 hr precipitallon on the righl side of the chart.
(4) Draw a line through the poinl paranel to the plotted lines.
(5) This Hne Is the lntensily-duralion curve lor the location
being analyzed .
Appllcallon Form:
(a) Selected frequency __ year
p (b) P6 • __ in., P24 = __ .~ = %121
24
(c) Adjuoled P5121 • __ In.
(d) Ix= __ min.
(e) I= __ ln.Jhr .
Note: This chart replaces the lntenslly-Durallon-Frequency
curves used since 1965.
1.S 2 2.S 3 3.5
I I I I I
S.S I
I 1 I.
Hydraflow Table of Contents DETENTION-UPDATED.gpw
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 05 / 8 / 2025
Watershed Mode I Schematic .................... • ............................................. _..................... 1
Hydrograph Return Period Recap.............................................................................. 2
100 -Year
Summary Report ......................................................................................................................... 3
Hydrograph Reports ................................................................................................................... 4
Hydrograph No. 2, Reservoir, OUTFLOW ................................................................................ 4
Pond Report-BASIN 1 OUTFLOW ..................................................................................... 5
ID F Report.................................................................................................................... 7
1
Watershed Model Schematic Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025
1
~t!f
V
•
Legend
l::bts1. Qd.gin Description
1 Manual BASIN 1 INFLOW
2 Reservoir OUTFLOW
Project: DETENTION-UPDATED.gpw Thursday, 05 I 8 I 2025
2
Hydrograph Return Period Rec~raflowHydrographs ExtensionforAutodesk®Civil3D®byAutodesk, Inc. v2025
Hyd. Hydrograph Inflow Peak Outflow (cfs) Hydrograph
No. type hyd(s) Description
(origin) 1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr
1 Manual ------------ ------------ ------ ------ ------------0.860 BASIN 1 INFLOW
2 Reservoir 1 --------------------------------------0.457 OUTFLOW
Proj. file: DETENTION-UPDATED.gpw Thursday, 05 / 8 I 2025
3
Hydrograph Summary _Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft) (ft) (cuft)
1 Manual 0.860 5 245 768 -----............ -----BASIN 1 INFLOW
2 Reservoir 0.457 5 250 745 1 44.59 153 OUTFLOW.
'
DETENTION-UPDATED.gpw Return Period: 100 Year Thursday, 05 / 8 / 2025
4
Hydrograph Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 05 I a I 2025
Hyd. No. 2
OUTFLOW
Hydrograph type
Storm frequency
Time interval
Inflow hyd. No.
Reservoir name
Storage Indication method used.
Q (cfs)
= Reservoir
= 100 yrs
= 5 min
= 1 -BASIN 1 INFLOW
= BASIN 1 OUTFLOW
Peak discharge
Time to peak
Hyd. volume
Max. Elevation
Max. Storage
OUTFLOW
Hyd. No. 2 --100 Year
= 0.457 cfs
= 4.17 hrs
= 745 cuft
= 44.59 ft
= 153 cuft
1.00 -.-------..----------,-------.--------..----------.-------.-
Q (cfs)
1.00
0.90 -i------1---------+-------+------1---------+-------+-0.90
0.80 -+------+-------+------+------+-----.....+--------+-0.80
... 0.70 -+------+-------+------+------+-----...+--------+-0.70
0.60 -+------+-------+------+------+--------IHI+------+ 0.60
0.50 -+------+-------+------+------+--------il-K+--------+-0.50 ----
-----0.40 --_-_-..:::.::.::::::---------+-------+------+---_-_-_-_-_--..------0.40
---
-----0.30 -+------+-------+------+------1-------------+-0.30
0.20 -+------+-------+------+------t------, ....... ----..... r-------t-0.20
-,11■-,,-----1.1------v--=\._---=
0.1 o t---=-=-=-=-=-=-=-=-~L-=-=-=-=-=-=-=-=--t===-=-=--t--====x.b ~-::--:.~=-=-=-:t=-=-=-~t•:::..-=-=-=---t 0.1 o ----fl~-f-~\ . ' 0.00 -1..::=::::::::::L....:::::::;_..t::::=:::::::t::::::::::";J.•:lll-===-----1==1:::5;;L. 0.00
0.0 0.8 1.7 2.5 3.3 4.2 5.0
-HydNo.2 -HydNo.1 II 1 1 I 11 II Total storage used= 153 cuft
Time (hrs)
Pond Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025
Pond No. 1 -BASIN 1 OUTFLOW
Pond Data
Contours -User-defined contour areas. Conic method used for volume calculation. Begining Elevation = 44.00 ft
Stage I Storage Table
Stage (ft) Elevation (ft) Contour area (sqft) Iner. Storage (cuft) Total storage (cuft)
0.00 44.00 197 0 0
0.25 44.25 245 55 55
0.50 44.50 298 · 68 123
0.75 44.75 353 81 204
1.00 45.00 413 96 300
Culvert/ Orifice Structures Weir Structures
[AJ [BJ [CJ [PrfRsrJ [AJ [BJ
Rise (in) = 6.00 4.00 Inactive 0.00 Crest Len (ft) = 4.00 Inactive
Span (in) = 6.00 3.00 0.00 0.00 Crest El. (ft) = 44.60 44.00
No. Barrels = 1 2 0 0 WeirCoeff. = 3.33 3.33
Invert El. (ft) = 41.00 44.10 0.00 0.00 Weir Type = 1 Rect
Length (ft) = 20.00 1.00 0.00 0.00 Multi-Stage = Yes No
Slope(%) = 2.00 0.00 0.00 n/a
N-Value = .013 .013 .013 n/a
Orifice Coeff. = 0.60 0.60 0.60 0.60 Exfil.(in/hr) = 0.000 (by Wet area)
Multi-Stage = n/a Yes No No TW Elev. (ft) = 0.00
5
Thursday, 05 / 8 / 2025
[CJ ~DJ
Inactive 0.00
0.00 0.00
3.33 3.33
No No
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
Stage I Storage I Discharge Table
Stage Storage Elevation ClvA ClvB ClvC PrfRsr WrA WrB WrC WrD Exfil User Total
ft cuft ft cfs cfs cfs cfs cfs cfs cfs cfs -cfs cfs cfs
0.00 0 44.00 0.00 0.00 0.00 0.00 0.000
0.03 6 44.03 1.53 OC 0.00 0.00 -0.00 0.000
0.05 11 44.05 1.53 OC 0.00 0.00 0.00 0.000
0.08 17 44.08 1.53 OC 0.00 0.00 0.00 0.000
0.10 22 44.10 1.53 oc 0.00 ic 0.00 0.00 0.000
0.13 28 44.13 1.53 OC 0.01 ic 0.00 0.00 0.007
0.15 33 44.15 1.53 OC 0.02 ic 0.00 0.00 0.019
0.17 39 44.18 1.53 OC 0.03 ic 0.00 0.00 0.035
0.20 44 44.20 1.53 OC 0.05 ic 0.00 0.00 0.054
0.22 50 44.23 1.53 OC 0.08 ic 0.00 0.00 0.075
0.25 55 44.25 1.53 OC 0.10 ic 0.00 0.00 0.099
0.28 62 44.28 1.53 OC 0.12 ic 0.00 0.00 0.125
0.30 69 44.30 1.53 oc 0.15 ic 0.00 0.00 0.152
0.32 75 44.33 1.53 OC 0.18 ic 0.00 0.00 0.182
0.35 82 44.35 1.53 OC 0.21 ic 0.00 0.00 0.213
0.38 89 44.38 1.53 OC 0.25 ic 0.00 0.00 0.246
0.40 96 44.40 1.53 OC 0.28 ic 0.00 0.00 0.280
0.43 103 44.43 1.53 OC 0.32 ic 0.00 0.00 0.315
0.45 109 44.45 1.53 OC 0.34 ic 0.00 0.00 0.344
0.48 116 44.48 1.53 OC 0.37 ic 0.00 0.00 0.366
0.50 123 44.50 1.53 OC 0.39 ic 0.00 0.00 0.388
0.52 131 44.53 1.53 OC 0.41 ic 0.00 0.00 0.408
0.55 139 44.55 1.53 OC 0.43 ic 0.00 0.00 0.427
0.57 147 44.58 1.53 OC 0.45ic 0.00 0.00 0.446
0.60 155 44.60 1.53 OC 0.46 ic 0.00 0.00 0.463
0.62 164 44.63 1.53 OC 0.48ic 0.05 0.00 0.533
0.6,5 172 44.65 1.53 OC 0.50 ic 0.15 0.00 0.646
0.67 180 44.68 1.53 OC 0.51 ic 0.27 0.00 0.786
0.70 188 44.70 1.53 OC 0.53 ic 0.42 0.00 0.950
0.72 196 44.73 1.53 OC 0.54 ic 0.59 0.00 1.132
0.75 204 44.75 1.53 OC 0.56 ic 0.77 0.00 1.332
0.77 214 44.78 1.55 OC 0.57 ic 0.98 0.00 1.547
0.80 223 44.80 1.65 OC 0.46 ic 1.19 0.00 1.654
0.82 233 44.83 1.70 OC 0.34 ic 1.36 s 0.00 1.697
0.85 242 44.85 1.71 OC 0.29 ic. 1.42 s 0.00 1.714
0.87 252 44.88 1.73 OC 0.26 ic 1.47 s 0.00 -1.727
0.90 262 44.90 1.74 OC 0.23 ic 1.51 s 0.00 1.737
0.92 271 44.93 1.75 OC 0.21 ic 1.54 s 0.00 1.746
Continues on next page ...
6
BASIN 1 OUTFLOW
Stage I Storage I Discharge Table
Stage Storage Elevation ClvA ClvB ClvC PrfRsr WrA WrB WrC WrD Exfil User Total
ft cuft ft -cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs cfs
0.95 281 44.95 1.76 QC 0.19 ic 1.56 s 0.00 1.754
0.97 290 44.98 1.76 QC 0.17 ic 1.59 s 0.00 1.762
1.00 300 45.00 1.77 QC 0.16 ic 1.61 s 0.00 1.770
... End
7
Hydraflow Rainfall Report
Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 05 I 8 / 2025
Return Intensity-Duration-Frequency Equation Coefficients (FHA)
Period
(Yrs) B D E (N/A)
1 0.0000 0.0000 0.0000 -------
2 69.8703 13.1000 0.8658 -------
3 0.0000 0.0000 0.0000 -----
5 79.2597 14.6000 0.8369 --------
10 88.2351 15.5000 0.8279 -------
25 102.6072 16.5000 0.8217 -----
50 114.8193 17.2000 0.8199 -------
100 127.1596 17.8000 0.8186 -----
File name: SampleFHA.idf
Intensity= B /(Tc+ D)AE
Return Intensity Values (in/hr)
Period
(Yrs) 5min 10 15 20 25 30 35 40 45 50 55 60
1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
2 5.69 4.61 3.89 3.38 2.99 2.69 2.44 2.24 2.07 1.93 1.81 1.70
3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 J
5 6.57 5.43 4.65 4.08 3.65 3.30 3.02 2.79 2.59 2.42 2.27 2.15
10 7.24 6.04 5.21 4.59 4.12 3.74 3.43 3.17 2.95 2.77 2.60 2.46
25 8.25 6.95 6.03 5.34 4.80 4.38 4.02 3.73 3.48 3.26 3.07 2.91
50 9.04 7.65 6.66 5.92 5.34 4.87 4.49 4.16 3.88 3.65 3.44 3.25
100 9.83 8.36 7.30 6.50 5.87 5.36 4.94 4.59 4.29 4.03 3.80 3.60
Tc= time in minutes. Values may exceed 60.
Precio file name· Sam□le.oco
Rainfall Precipitation Table (in)
Storm
Distribution 1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr
SCS 24-hour 0.00 2.20 0.00 3.30 4.25 5.77 6.80 7.95
SCS 6-Hr 0.00 1.80 0.00 0.00 2.60 0.00 0.00 4.00
Huff-1st 0.00 1.55 0.00 2.75 4.00 5.38 6.50 8.00
Huff-2nd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-3rd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-4th 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-Indy 0.00 0.00 0.00 0.00 0.00 0;00 0.00 0.00
Custom 0.00 1.75 0.00 2.80 3.90 5.25 6.00 7.10
DRAINAGE STUDY-50J0AVENIDA ENCINAS
APPENDIX2
EXISTING & PROPOSED
DRAINAGE EXHIBITS
SPETEMBER 2024
5010 A VEN/DA ENCINAS -EXISTING CONDITION HYDROLOGY WORKMAP
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CARLSBAD, CA 92008
Plot May 08, 2025 at 12: 43pm P: \ACTIVE JOBS\2439_Carlsbad 10 Hospitallity\CIVIL \REPORTS\HYDROLOGY\2439-HYDE.dwg
w
SCALE:
0
N
s
LEGEND
PROPERTY UNE
RIGHT-OF-WAY
ROAD CENTERUNE
ADJACENT PROPERTY UNE
DRAINAGE BASIN BOUNDARY
DRAINAGE FLOW PATH
PRE-PROJECT IMPER'AOUS AREA
FLOW ARROW
BASIN SUMMARY
AREA CALCULATIONS
TOTAL AREA
PER'AOUS AREA
IMPER'AOUS AREA
% IMP
7,782 S.F. (0.179 AC)
7,079 S.F. (0.16J AC)
685 S.F. (0.016 AC)
8.80%
- -
EX1
x.x x.x
SF CFS
E "~ 1" = 20' VA N RVN
CIVIL ENGINEERING I LAND SURVEYING
20 40 San Diego I Manteca I 858.521 .8100
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5010 A VEN/DA ENCINAS -PROPOSED CONDITION HYDROLOGY WORKMAP
CARLSBAD, CA 92008
7"' ' '
'4 I ·• ~ ,f ',
'·.., • .J,' ,4
ES
SCALE:
LEGEND
PROPERTY UNE
RIGHT-OF-WAY
ROAD CEN1ERUNE
ADJACENT PROPERTY UNE
DRAINAGE BASIN BOUNDARY
DRAINAGE Fl.OW PATH
POST-PRO£CT IMPER'AOUS AREA
&<'..
~ POST-PRO£CT DE MIN/MIS AREA
s
1" = 20·
20
Fl.OW ARROW
BASIN SUMMARY
TOTAL IMPER'AOUS AREA
NEW/REPLACED IMPER'AOUS AREA
% IMP
40
- -
ttls-3:ZI
I ...
r· . ] • • • • • ·: ................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
---------
2,525 S.F. (0.058 AC)
5,257 S.F. (0.121 AC)
4,821 S.F. (0.11 AC)
67.55%
"~ VAN RVN
CIVIL ENGINEERING I LAND SURVEYING
San Diego I Manteca I 858.521.8100
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