HomeMy WebLinkAboutLot 9 Hydrology (Nov.9,2005) � . O FM Ag35O a
Lot q
H YDRO LOG Y D
Community Sports Park
Roripaugh Ranch
Temecula, California
Prepared for:
Hirsch & Associates
2221 East Winston Rd., Suite A
Anaheim, CA 92806
Prepared by:
Blue Peak Engineering, Inc.
646 North Sepulveda
Placentia, CA 92870
(714) 749 -3077
November 9, 2005
oQ VF ESSIO
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Prepared under the supervision of Blue Peak Engineering, Inc: 4 m
N0. C06048
Exp. !/&'6' ,x
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ql F OF C AO,
Rob DePrat, RCE 60482 Date
Hydrology Study
COMMUNITY SPORTS PARK - TEMECULA, CA
Table of Contents
SectionI Project Description .................................................... ............................... 1
SectionII Methodology .............................................................. ............................... 2
Section III Hydrology Calculations ............................................. ............................... 8
SectionIV Conclusion ................................................................. .............................10
Attachments
Appendix A .......................................... ............................... Location /Vicinity Map
AppendixB ................................................... ............................... Hydrology Map
Appendix C ........... ............................... Riverside County Hydrology Manual Plates
Hydrology Study
COMMUNITY SPORTS PARK— TEMECULA, CA
Sedion I Project Description
INTRODUCTION
This report has been prepared to analyze the hydrological effects of the proposed Community Sports Park
site development as part of the master - planned community of Roripaugh Ranch. The proposed site flows
will be calculated for each exit point from the development.
EXISTING DRAINAGE PATTERN
The existing site consists of approximately 19.5 acres of rough graded dirt located at the southeast corner
of North Loop Road and Butterfield Stage Road in the City of Temecula, California (See Vicinity Map in
Appendix A). The existing drainage pattern splits the property into two sections. Approximately 2 acres
at the northwest corner of the site drains into the Santa Gertrudis Wash which runs through the northwest
portion of the site. The remainder of the site sheet flows into the Long Valley Channel to the south of the
site.
PROPOSED DRAINAGE PATTERN
The site is a portion of the Roripaugh Ranch Development and will serve as a community sports park for
the overall master - planned community. The proposed developed site includes the construction of a
community sports park containing sports fields, concession stands and a paved parking lot. Drainage will
be collected through a series of drainage swales and catch basins throughout the site emptying into an
underground storm drain system. This storm drain system will divert runoff offsite at four distinct exit
points. The four exit points are as follows:
1) Sheet flow onto North Loop Road
2) Proposed storm drain system entering Santa Gertrudis Wash
3) Proposed storm drain system entering Long Valley Channel (East)
4) Proposed storm drain system entering Long Valley Channel (West)
These locations are shown graphically on the Hydrology Map in Appendix B of this report.
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November 9, 2005
Hydrology Study
COMMUNITY SPORTS PARK — TEMECULA, CA
Sedi on 1 I Methodology
RUNOFF DETERMINATION METHODS
The two primary methods used by the Riverside County Flood Control District to determine design
discharges are the Rational method and the Synthetic Unit Hydrograph method. The Rational method is
generally intended for use on small watersheds of less than 300 to 500 -acres while the Synthetic Unit
Hydrograph method is intended for use on watersheds in excess of these limits. For the purposes of this
report, we will be using the Rational Method.
PHYSIOGRAPHIC CHARACTERISTICS
Topography
The Riverside County Flood Control District encompasses portions of three major river basins: the Santa
Ana, the Santa Margarita and the Whitewater. The entire San Jacinto River Basin, a 768 square mile
tributary of the Santa Ana River, is located within District boundaries. The San Jacinto River is regulated
by natural storage in Lake Elsinore, and rarely contributes flow to the Santa Ana River, the last
occurrence being in 1916. This project is located within the Santa Margarita Watershed.
Geology and Soils
The extremely varied topography in the region is a result of extensive fault systems crossing the area and
erosive weathering. The mountain ranges are essentially a product of this faulting and run roughly parallel
to one another, and to the largest fault zones. The three major fault zones are the Elsinore, San Jacinto
and San Andreas. The Elsinore fault parallels the northeasterly toe of the Santa Ana Mountains, while the
San Jacinto and San Andreas faults lie at the southwesterly toe of the San Jacinto and Little San
Bernardino Mountains, respectively.
In mountainous areas soil depths are extremely shallow, and on many of the steepest slopes soil cover is
virtually non - existent with bedrock exposed. Infiltration capacity is extremely limited in such areas. In the
valley areas alluvial soils predominate, but extreme variations do exist in the depth and nature of the
alluvial deposits. In general, the alluvial cones or fans near canyon mouths are coarse and extremely
porous. The materials further downstream tend to become finer and less porous with distance from the
source. Some valley areas have extremely low infiltration rates due to high clay content in the alluvium.
The soil properties for this project are classified in Group D. Group D consists of soils having very slow
infiltration rates when thoroughly wetted and consisting chiefly of clay soils with a high swelling
potential, soils with a permanent high water table, soils with a claypan or clay layer at or near the surface,
and shallow soils over nearly impervious material. These soils have a very slow rate of water
transmission.
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Hydrology Study
COMMUNITY SPORTS PARK — TEMECULA, CA
Hydrometeorological Characteristics
The three types of storms which can occur over the District are general winter storms, general summer
storms and high intensity thunderstorms. Most precipitation results from the general winter storms which
normally occur in the late fall or winter months and may have durations of several days. General winter
storms occur when, as the result of extratropical cyclones, warm moisture laden Pacific air masses move
inland over Southern California. Orographic lifting and cooling of the air masses results in increasing
precipitation as they move eastward over the coastal plain and Santa Ana Mountains. Precipitation rates
decrease over the inland valleys, but as the air masses are subjected to more extensive lifting upon rising
over the major interior mountain ranges high rates of precipitation occur. As the storm continues eastward
beyond the mountains little moisture remains and precipitation decreases rapidly over the desert areas.
INTENSITY - DURATION CURVES
Intensity- duration data is required for use with the Rational Method. This data is usually presented in the
form of curves of rainfall intensity in inches per hour versus storm duration in minutes. Standard
intensity- duration curves have been published in master plan studies for many areas of the District. In
areas where these curves are still applicable they should be used in the interest of consistency. A tabular
presentation of current intensity- duration data for many of the population centers throughout the District
are presented on Plate D -4 .1. The intensity- duration curve data shown in Plate D -4.1 (Murrieta —
Temecula & Rancho California) was used for this project and can be seen in Appendix C of this report.
INFILTRATION
General
Infiltration is the process of water entering the soil surface. In Riverside County Flood Control District
design hydrology, infiltration is expressed as the rate in inches per hour at which precipitation enters the
soil surface and is stored in the subsurface structure. Among the many factors affecting infiltration or loss
rates, three of the most important are: soil surface and profile characteristics, soil cover or vegetation type,
and antecedent moisture conditions. During a storm event loss rates tend to decrease with time, although
in design hydrology a constant average loss rate is often assumed.
In the following paragraphs major factors affecting infiltration are discussed in detail, and methods are
described for estimating loss rates for use in District design hydrology. The methods described are based
on general information, and therefore are intended only as a guide in estimating loss rates; however, it is
believed that when properly applied by experienced engineers and hydrologists they will yield reasonable
results.
Hydrologic Soil Groups
The major factor affecting infiltration is the nature of the soil itself. The soils surface characteristics,
ability to transmit water through subsurface layers and total storage capacity are all major factors in the
infiltration capabilities of a particular soil. The Soil Conservation Service (SCS) of the U.S. Department
of Agriculture has investigated the hydrologic characteristics of soils as related to runoff potential, and
has developed a system useful to the District to classify soils into four hydrologic soils groups as follows:
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Hydrology Study
COMMUNITY SPORTS PARK — TEMECULA, CA
Group A - Low runoff potential. Soils having high infiltration rates even when thoroughly wetted and
consisting chiefly of deep, well to excessively drained sands or gravels. These soils have a high rate of
water transmission.
Group B - Soils having moderate infiltration rates when thoroughly wetted and consisting chiefly of
moderately deep to deep, moderately well to well drained soils with moderately fine to moderately coarse
textures. These soils have a moderate rate of water transmission.
Group C - Soils having slow infiltration rates when thoroughly wetted and consisting chiefly of soils with
a layer that impedes downward movement of water, or soils with moderately fine to fine texture. These
soils have a slow rate of water transmission.
Group D - High runoff potential. Soils having very slow infiltration rates when thoroughly wetted and
consisting chiefly of clay soils with a high swelling potential, soils with a permanent high water table,
soils with a claypan or clay layer at or near the surface, and shallow soils over nearly impervious material.
These soils have a very slow rate of water transmission.
The SCS and U. S. Forest Service (USFS) have mapped soil types and assigned hydrologic soils
classifications in many areas of the District. Using this information the District has compiled generalized
hydrologic soils classification maps. These maps are shown on Figures C1.01 through C -1.66 of the
Riverside County Hydrology Manual. This project falls in Soil Group D as shown on Figure C -1.53 in
Appendix C of this report.
Soil Cover Type
The type of vegetation or ground cover on a watershed, and the quality or density of that cover, have a
major impact on the infiltration capacity of a given soil. In consideration of cover type and quality the
District uses a system developed by the SCS, whose studies on the affect of cover type on runoff potential
are believed to represent the most comprehensive information available for this region. Detailed
descriptions of these cover types grouped in three broad classifications (Natural, Urban, and Agricultural)
are given on Plate C -2. Definitions of cover quality are as follows:
Poor - Heavily grazed or regularly burned areas. Less than 50 percent of the ground surface is
protected by plant cover or brush and tree canopy.
Fair - Moderate cover with 50 percent to 75 percent of the ground surface protected.
Good - Heavy or dense cover with more than 75 percent of the ground surface protected.
For the purposes of this report, a cover, type of urban landscaping was used.
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Hydrology Study
COMMUNIT SPO RTS PARK — TEMECULA, CA
Antecedent Moisture Conditions
Antecedent moisture condition (AMC) has a major effect on the runoff potential of a particular soil -cover
complex. AMC can be defined as the relative wetness of a watershed just prior to a flood producing storm
event. AMC is sometimes expressed as the amount of rainfall occurring in a specific period of time prior
to a major storm. Such evaluations are crude at best due to the importance of the time distribution of
rainfall within the antecedent period, etc. For this reason the District uses the following generalized
definitions of AMC levels:
AMC I - Lowest runoff potential. The watershed soils are dry enough to allow satisfactory grading or
cultivation to take place.
AMC II - Moderate runoff potential, an intermediate condition.
AMC III - Highest runoff potential. The watershed is practically saturated from antecedent rains.
In rainfall based hydrology methods it is normally true that a low AMC index (high loss rates) should be
used in developing short return period storms (2 -5 year); and a moderate to high AMC index (low loss
rates) should be used in developing longer return period storms (10 — 100 year). For the purposes of
design hydrology using District methods, AMC II should normally be assumed for both the 10 year and
1.00 year frequency storm. In the case of spillway hydrology for dams or debris basins, a condition
between AMC II and AMC III should be assumed depending on the degree of risk involved in failure of
the structure. Since this report contains the results for a 10 -year storm event, an AMC II condition will be
used for the calculations.
Impervious Areas
Discussion in the previous paragraphs has dealt entirely with infiltration for pervious surfaces. In
analyzing developed areas the effect of impervious surfaces on the average infiltration rate over the entire
watershed must be considered. Estimated ranges of impervious percentages for various types of
development are given on Plate D -5.6 or E -6.3 (identical Plates). Values given are for the actual
percentage of area covered by impervious surfaces; however, studies have shown that effective
impervious area is generally smaller than actual impervious area. A number of reasons for this difference
can be cited, i.e., an impervious surface discharging onto a pervious surface where infiltration may take
place, evaporation from local depression storage, pervious area under the overhang of rooftop eaves, etc.
The difference between effective and actual impervious area generally is larger for short return period
storms (2 - 5 year), and smaller for longer return period storms (10 - 100 year). To account for the
difference between actual and effective impervious areas in District hydrology, actual impervious area is
assumed to be 90 percent effective during design storms. This adjustment is made in the computation of
runoff coefficients for the Rational method, and in the computation of adjusted loss rates for the Synthetic
Unit Hydrograph method.
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Hydrology Study
COMMUNITY SPO RTS PARK — TEMECULA, CA
RATIONAL METHOD
General
The Rational method is commonly used for determining peak discharge from relatively small drainage
areas. The Rational method is based on the following equation:
Q = CIA, where:
Q = Peak discharge - cfs
C = Coefficient of runoff
I = Rainfall intensity (inches/hour) corresponding to the time of concentration
A = Area — acres
Time of Concentration
If rain were to fall continuously at a constant rate and be uniformly distributed over an impervious
surface, the rate of runoff from that surface would reach a maximum rate equivalent to the rate of rainfall.
This maximum would occur when all parts of the surface were contributing runoff to the concentration
point. The time required to reach the maximum or equilibrium runoff rate is defined as the time of
concentration. The time of concentration is a function of many variables including the length of the flow
path from the most remote point of an area to the concentration point, the slope and other characteristics
of natural and improved channels in the area, the infiltration characteristics of the soil, and the degree and
type of development. In District Rational tabling, the time of concentration for an initial sub -area can be
estimated from the nomograph on Plate D -3, as shown in Appendix C of this report. The time of
concentration for the next downstream subarea is computed by adding to the initial time, the time required
for the computed peak flow to travel to the next concentration point. Time of concentration is computed
for each subsequent subarea by computing travel time between subareas and adding the cumulative sum.
Intensity- Duration Curves
Rainfall intensity, "I ", is determined using District intensity- duration curves for the area under study.
Standard intensity- duration curves have been prepared for many population centers in the District.
Intensity- duration data for these standard curves is given in tabular form on Plate D -4.1. The standard
intensity- duration curve used for this project is shown on Plate D -4.1 (Murrieta — Temecula & Rancho
California) in Appendix C of this report.
Coefficient of Runoff Curves
The coefficient of runoff is intended to account for the many factors which influence peak flow rate. The
co- efficient depends on the rainfall intensity, soil type and cover, percentage of impervious area,
antecedent moisture condition, etc. To account for the difference between actual and effective impervious
area it is assumed the maximum runoff rate which can occur from impervious surfaces is 90- percent of
the rainfall rate. The runoff from pervious surfaces is further reduced by infiltration.
The infiltration rate for pervious areas, "F ", can be estimated using the methods discussed in the
Riverside County Hydrology Manual for various combinations of soil type, cover type and antecedent
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Hydrology Study
COMMUNITY SPOR PARK — TEMECULA, CA
moisture condition (AMC). In practice it is not necessary for the engineer to make these computations, as
runoff coefficient curve data has been tabulated by the District on Plate D -5.7 for the working range of
runoff index (RI) numbers. Runoff coefficient curves can be developed for any combination of conditions
by simply plotting the data from Plate D -5.7 on Plate D -5.8. In addition, for the common case of urban
landscaping type cover, runoff coefficient curves have been plotted on Plates D -5.1 through D -5.4.
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Hydrology Study
COMMUNIT S PORTS PARK - TEMECULA, CA
Secti on I I I Hyd rology Ca Icu lations
Runoff Calculations
Using the Riverside County Hydrology Manual, the proposed runoff for the project was calculated for the
10 -Year Storm Event. The runoff from this project exits the site at four separate points. These points of
exit, as well as the sub -area locations are shown on the Hydrology Map in Appendix B of this report. The
runoff calculations are shown in the following tables.
TABLE 1
SUB -AREA ANALYSIS (10 -YEAR STORM)
Area Storm Soil C Tc I A Q
No. Freq. Group (in /hr) (acres) (cfs)
Al r10 D 0.78 12.0 2.130 0.50 0.83
A2 D 0.80 8.0 2.670 0.67 1.43
A3 D 0.79 10.0 2.360 3.14 5.85
A4 D 0.79 11.0 2.240 2.47 4.37
A5 D 0.89 16.0 1.820 1.86 3.01
A6 10 D 0.79 10.0 2.360 1.22 2.27
A7 10 D 0.77 15.0 1.890 2.92 4.25
A8 10 D 0.77 14.0 1.960 3.04 4.59
A9 10 D _ 0F7 _
.77 14.0 1.960 3.72 5.61
A10 10 D 0.78 12.0 2.130 1.42 2.36
TABLE 2
SHEET FLOW ONTO NORTH LOOP ROAD
Area Storm I Soil I C Tc Ttot I A Atot Q Qdes Dia. Slope Velocity Length Travel
No. From To Freq. Group (min) (in/hr) (acres) (cfs) (in) (ft/sec) (ft) Time (min)
Al 10 1 D 1 0.78 1 12.0 1 12.1301 0.50 1 1 0.83
TABLE 3
PROPOSED STORM DRAIN SYSTEM ENTERING SANTA GERTRUDIS WASH
Area Storm Soil C Tc Ttot I A Atot Q Qdes Dia. Slope Velocity Length Travel
No. From To Freq. Group (min) (in /hr (acres) (cfs) in ft/sec) (ft) Time (min
FA1 10 D 0.78 12.0 2.130 1.42 2.36
A10 A2 12" 0.0059 3.92 337 1.43
10 D 0.79 10 2.240 314 5.56 A3 A2 18" 0.0060 4.96 165 0.55
10 D 0.80 8.0 2.670 0.67 1.43
A2 A2 _
AZ 10 D 0.79 13.43 2.000 5.23 8.26
I_F KE _ ND l
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Hydrology Study
COMMUNITY S PORTS PARK - TEMECULA, CA
TABLE 4
PROPOSED STORM DRAIN SYSTEM ENTERING LONG VALLEY CHANNEL
(EAST END OF SITE)
Area Storm Soil C Tc I Ttot I I I A I Atot Q Qdes Dia. Slope Velocity Length Travel
No. From To Freq. Group (min) (in /hr) (acres) (cfs) (in) (ft/sec) (ft) Time (min)
A5 10 D 10.891 16.0 11.8201 1.86 1 3.01
TABLE 5
PROPOSED STORM DRAIN SYSTEM ENTERING LONG VALLEY CHANNEL
(WEST END OF SITE)
Area Storm Soil C Tc I Ttot I A Atot Q Qdes Dia. Slope Velocity Length Travel
No. From To Freq. Group (min) (in/hr) (acres) (cfs) (in) (ft/sec ) (ft) Time (min)
A4 10 D 0.79 11.0 2.240 2.47 4.37
A4 A7 18" 0.0120 6.07 194 0.53
A6 10 D 0.79 10.0 2.360 1.22 2.27
A6 A7 8" 0.0300 6.74 64 0.16
A7 10 D 0.77 15.0 1.890 2.92 4.25
A7 A7
A7 10 D 6.80 k15.00 1.890 6.61 9.99
A7 A8 18" 0.0360 11.76 41 0.06
A8 10 D 0.77 14.0 1.960 3.04 4.59
A8 A8
A8 10 D 0.80 15.06 1.880 9.65 14.51
A8 A9 24" 0.0100 7
7.64 464 1.01
A9 10 D 0.77 14.0 1.960 3.72 5.61
A9 A9
A9 10 D 0.79 16.07 1.810 13.37 19.12
A9 END
I
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COMMUN S PORTS PARK — TEMECULA, CA
Section IV Conclusion
Runoff Summary
The following table shows the location the runoff exits the site with its corresponding runoff rate for the
10 -year storm event. These locations are shown graphically on the Hydrology Map in Appendix B of this
report.
Description Runoff
Sheet flow onto North Loop Road 0.83 cfs
Proposed storm drain system entering Santa Gertrudis Wash 8.26 cfs
Proposed storm drain system entering Long Valley Channel (East) 3.01 cfs
Proposed storm drain system entering Long Valley Channel (West) 19.12 cfs
Page 10
November 9, 2005
qP
Appendix A
LocationNicinty Map
215 y
RORIPAUGH
RANCH
M Rierq HOT SPRINpS ROgp a PROJECT
15 &
0
CALLE CHAP
N1O RD
79 u p
3 w
[Z LA SERENA WY
w
15���
� m
VICINITY MAP
NOT TO SCALE
RIETA HOT SPRINGS ROAD
1 3 8 MGRRIETq "O>
7B 1 A 2 5 3 4A A 10 9B
4B 13
7C 6 11
7A
NAP
12
33B 16 17 19
33A 14 15 \
30
29 18
SITE 27 2 31
26 22
24 23 25
21 20
32
LOCATION MAP 19
NOT TO SCALE
Appendix B
Hydrology Map
_ AREA SUMMARY
a ` ,�
A� AC � AC A� AC Q�
I I EXIT TO H =4.5' H =9' H =20'
L =M1 L =170' L =350'
� i AREA 2 SANTA GE RUD AS_N T c` =0. 8 I c 0 8o' c=0. 79 MlN.
1 =213 1NIHR 1 =267 /N /HR 1 =236 /N /HR
0 =0.83 CFS 0 =1.43 CFS 0 =5.85 CFS'
AREA 5 Q A 4j Ac A te` 1�es Ac Ai 11 Ac
RMN'LRB /p BU! RECBpB
OATE pESpPDpR
H =20' H=11' H =15'
L =385' L =620' L =325'
1 Tc =11 MIN., Tc =16 MIN. Tc =10 MIN.
Lu AREA 3 C =O. 79 i C = 0.89 C =0.79
1 =224 /NAR 1 =1.82 /N /HR 1 =236 /N /HR
0 0 =4.37 CFS 0 -3.01 CFS 0 =227 CFS
IQ � - AREA 7 A REA 8 AREA 9
Q A =292 AC A =304 AC A =372 AC
I I H =20' H =12' H= 10'
I AREA 4 Tc 15 MIN., Tc 514 MIN. Tc 4 94 MIN.
AREA 10 I C=O. 77 c =o. n C=O. 77 REV W011
W I 0 /= 1.89.1N/�'R / =1.96 IN /HR 1 =1.96 /N /HR DALE DOW TO
0 =4.15 CF5 0 =4.59 CFS 0 =561 CFS
p AREA 10
o I A =1.42 AC
H =25'
L =250'
Tc =12 MIN.
I V C= 0.78'.: =;
1 =213 /N /HR
0 =236 CFS
AREA ? ° I!, AREA 6 LEGEND MB,ecfppEre
\`
N OUTLINE OF SUB AREA
AREA 9 AREA 8 Rulvo 1- suMMARr o Q
I
1 1 0 SHEET FL7 OFF51TE 0.83 CFS y
0 0 EXIT TO SANTA GERTRUD15 WASH 8.16 CF5
1 A 0 \ EXIT TO LONG VALLEY CHANNEL (EAST) 3.01 CFS i c
wl C Z 0
EXIT TO LOVG VALLEY CHANNEL (WEST) 19.12 CFS a
1000 �'� —+ m�
F" Q
C t
l o a m
EXIT TO
LONG VALLEY CN NNEL (WEST)
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1 OF
Appendix C
Riverside County Hydrology Manual Plates
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B ACHELOR
TC' LIMITATIONS:
L 100 I. Maximum length =1000 TC
1000 90 2. Maximum area = 10 Acres 5
900 80 a
o H 6 d
800
70 0
400 Q
`0 300
700 60 � > 200 7
o 100 E
a
w N E E
— 8 oa
600 0 50 o 0 60
c c�
-� E ° > 30 9 0
CL .- 20
500 0 (�) a ° , a °' 1
0 10
d
w d 35 ° m 8 10 v
m H 3 6 LL.
w K Ai (I) I I
c 400 ,° , 30 Undeveloped 0 m 12
Good Cover w in
a-350 25 Undeveloped 0 1. 0
_c Fair Cover .6 14 w
° E = s U)
300 Undeveloped 0 c :a l 21 15
9 c c Poor Cover 2
c - ; i8 Single Family 5 0 m 17 c
250 (1/4 Acre) m 18
16 -
J
L o 15 Commercial 0 19
14 20
(Pav °
200 13 ° c
o
a� w
J 12
cg II 25 v
, c
° KEY
150 9 L- H -Tc - K-Tc' o
30
8 E
EXAMPLE: E
7 (1) L =550', H =5.0, K = Single Family (1/4 Ac.) 35
Development , Tc = 12.6 min.
6
100 (2) L =550', H =5.0', K = Commercial 40
Development , Tc = 9.7 min.
5
4 Reference: Bibliography item No. 35.
R C F C Ek W C® TIME OF CONCENTRATION
HYDR 1\/JANUAL FOR INITIAL SUBAREA
PLATE D -3
RAINFALL INTENSITY- INCHES PER HOUR
MIRA LOMA MURRIETA - TEMECULA NORCO PALM SPRINGS PERRIS VALLEY
& RANCHO CALIFORNIA
C) DURATION FREQUENCY DURATION FREQUENCY DURATION FREQUENCY DURATION FREQUENCY DURATION FREQUENCY
MINUTES MINUTES MINUTES MINUTES MINUTES
0 10 100 10 100 10 100 10 100 10 100
(j7 YEAR YEAR YEAR YEAR YEAR YEAR YEAR YEAR YEAR YEAR
5 2.84 4.48 5 3.45 5.10 5 2.77 4.16 5 4.23 6.76 5 2.64 3.78
6 2.58 4.07 6 3.12 4.61 6 2.53 3.79 6 3.80 6.08 6 2.41 3.46
7 2.37 3.75 7 2.87 4.24 7 2.34 3.51 7 3.48 5.56 7 2.24 3.21
8 2.21 3.49 8 2.67 3.94 8 2.19 3.29 8 3.22 5.15 8 2.09 3.01
D 9 2.08 3.28 9 2.50 3.69 9 2.07 3.10 9 3.01 4.81 9 1.98 2.84
v 10 1.96 3.10 10 2.36 3.48 10 1.96 2.94 10 2.83 4.52 10 1.88 2.69
11 1.87 2.95 11 2.24 3.30 11 1.87 2.80 11 2.67 4.28 11 1.79 2.57
r 12 1.78 2.82 12 2.13 3.15 12 1.79 2.68 12 2.54 4.07 12 1.72 2.4
13 1.71 2.70 13 2.04 3.01 13 1.72 2.58 13 2.43 3.88 13 1.65 2.3
14 1.64 2.60 14 1.96 2.89 14 1.66 2.48 14 2.33 3.72 14 1.59 2.29
15 1.58 2.50 15 1.89 2.79 15 1.60 2.40 15 2.23 3.58 15 1.54 2.21
16 1.53 2.42 16 1.82 2.69 16 1.55 2.32 16 2.15 3.44 16 1.49 2.1♦
17 1.48 2.34 17 1.76 2.60 17 1.50 2.25 17 2.08 3.32 17 1.45 2.08
18 1.44 2.27 18 1.71 ?.52 18 1.46 2.19 18 2.01 3.22 18 1.41 2.02
19 1.40 2.21 19 1.66 2.45 19 1.42 2.13 19 1.95 3.12 19 1.37 1.97
20 1.36 2.15 20 1.61 2.38 20 1.39 2.08 20 1.89 3.03 20 1.34 1.92
22 1.29 2.04 22 1.53 2.26 22 1.32 1.98 22 1.79 2.86 22 1.28 1.83
24 1.24 1.95 24 1.46 2.15 24 1.26 1.90 24 1.70 2.72 24 1.22 1.75
26 1.18 1.87 26 1.39 2.06 26 1.22 1.82 26 1.62 2.60 26 1.18 1.69
28 1.14 1.80 28 1.34 1.98 28 1.17 1.76 28 1.56 2.49 28 1.13 1.63
30 1.10 1.73 30 1.29 1.90 30 1.13 1.70 30 1.49 2.39 30 1.10 1.57
32 1.06 1.67 32 1.24 1.84 32 1.10 1.64 32 1.44 2.30 32 1.06 1.52
Z 34 1.03 1.62 34 1.20 1.78 34 1.06 1.59 34 1.39 2.22 34 1.03 1.48
36 1.00 1.57 36 1.17 1.72 36 1.03 1.55 36 1.34 2.15 36 1.00 1.44
n
rn 38 .97 1.53 36 1.13 1.67 38 1.01 1.51 38 1.30 2.09 38 .98 1.40
Z 40 .94 1.49 40 1.10 1.62 40 .98 1.47 40 1.27 2.02 40 .95 1.37
X 0 N 45 .89 1.40 45 1.03 1.52 45 .92 1.39 45 1.18 1.89 45 .90 1.29
50 .84 1.32 50 .97 1.44 50 .88 1.31 50 1.11 1.78 50 .85 1.22
55 .80 1.26 55 .92 1.36 55 .84 1.25 55 1.05 1.68 55 .81 1.17
rn z 60 .76 1.20 60 .88 1.30 60 .80 1.20 60 1.00 1.60 60 .78 1.12 Aft
I 0 65 .73 1.15 65 .84 1.24 65 .77 1.15 65 .95 1.53 65 .75 1.08
r D 70 .70 1.11 70 .81 1.19 70 .74 1.11 70 .91 1.46 70 .72 1.04
D 0 c 75 .68 1.07 75 .78 1.15 TS .72 1.07 75 .88 1.41 75 .70 1.00
m D 0 BO .65 1.03 BO .75 1.11 80 .69 1.04 80 .85 1.35 80 .68 .97
D D 85 .63 1.00 85 .73 1.07 85 .67 1.01 85 .82 1.31 85 .66 .94
p Q SLOPE _ .530 SLOPE _ .550 SLOPE _ .500 SLOPE _ .580 SLOPE _ .490
z
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.: INFALL INTENSITY IN INCHES PER HO
•