HomeMy WebLinkAbout3338; Agua Hedionda & Calavera Creek Dredging; Flood Control; 1989-07-015,ep. 3 '96 12:02 MFINITOU FRX 275 FFIX 6197457487 P. 3
HYDROLOGICAL STUDY
FOR NORTHEASTERN CARLSBAD
BASINS OF CALAVERA LAKE CREEK
AND AQUA HEDIONDA CREEK
prepared by
Howard ti. Chang
Ph.D.. P.E.
July 1989
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TABLE OF a"R4TS
I. INTRODOCYION -.-.............,..............-....................*,, 1
11. DRAINAGE BASIN QIARACTERImICS ..................................... 2
111. S'IDRAGE ROUTING WROOGH QLLAVERA wu(E ............................ 5
IV. RESULTS OF HYDR0UX;Y SrUDY ......................................... 7
V. FUX;D PLAIN STUDY FOR MIBILE HOME PARK ............................. 10
VI. REOM"DATI0NS FOR DRAINAGE 1HPR"T .......................... 11
REFERENCES .............................................................. 12
FIGJRES
AF'PplDIX A: INWT/WTPUT LISTINGS OF HYOROMGY SIVDY (HEC-1)
APPENDIX B. INPVT/OOTPOT LISTINGS OF HEC-2 ,Sl'LlDY ECJR WILE HOME PARK
AlTXHMWTS
b Drainage Map of Calavera Lake Creek and Aqua Hedionda Creek
Flood Plain Map at Mobile Hare Park
Sep. 3 '96 12:03 MANITOU FAX 275 FAX 6197457487
1. INTRWCfION
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P. 5
This hydrology study was made for the northeastern quadrant of the City of
Carlsbad, covering Zones 7, 14, and 15. The area is drained by two major
streams: Aqua HedlOnda Creek and Calavera Lake Creek, as shown in the attached
maps. The prpose of the study is to obtain the 100-year flood discharges of
streams within thedesignated zones. Recarmendations will also bemade to solve
the inadequate drainage situation of Calaveta Lake Creek through the Rancho
Calsbad Mobile ~ane Park. A unified approach in hydrology is applied to all
streams in these zones. The hydrology study considers the ultimate developnent
under the established developnent constraints, so that the results are also valid
in the long tern.
This study is guided by the Hydrology Manual of the county of San Diego,
updated in 1985. As specified in the manual, the s(5 method for hydrology shall
be applied to drainage basins that are larger than 0.5 square mile. The HEG~
canputer model developed by the U. S. Army Corps of Engineers, which employs the
SCS method, is the principle tool for this study. The drainage basins as
Selected in this stu6y are also parte Of larger basins which extend outslde the
clty limit. For each case, the entire drainage basin is included in the
caprtataon, as shown in the drainage basin map.
me ~ydrology Manual also specifies the use of the rational method for
draipage basins that are less than 0.5 square mile in area. Tk rational method
is a simpler methcd which provides the design discharge of specific drain
facilities. This study does not cover the rational method since such facilities
are selected with future developnent.
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MRNITOU FRX 275 FRX 6197457487 P. 6
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An imptent objective of the present study is to develop an adequate means
of drainage for themobile ham park. The existing shallow channel through the
park is silted and inadequate to. convey th&rlOO-year flood. A suitable
configuration of the channel, subject to given physical constraints, shall be
determined. Reduction of thc flood discharge, if necessary, using flood water
detention basins or operation method of Calavera Lake are mng the alternatives
to be investigated.
The flood level and flood plain boundary of AqUa Wionda Creek through the
Rancho Carlsbad Mobile Haw Park is canplted using the HEC2 program for the
discharges determined in this hydrology study. However, channel improvement,
if needed, is rot investigated in this study.
11. DRAINAGE WIN aiMACl‘ERISPICS
Drainage basins are delineated for the northeastern area of the City within
Zones 7, 14, and 15. points of concentration along the principal drainage
courses are also delineated on the drainage map.
L.
For the prpose of hydrological canputation, certain basin characteristics
are required. Such characteristics include basin area, precipitation zone nunber
(PZN) , antecedent moisture condition, precipitation, SCS curve nunber (a), lag
the, etc. Methods for obtaining such characteristics are described below
separately.
Basin Mea - The area of a drainage besin iS measured directly fran the
Work maps used for this plrpose have scales equal to or drainage basin map.
greater than 1” = 400’.
Precipitation zone Nunber (PZN) - This value for a basin is obtained from
Fig. 14-3 of the county Hydrology Wnual. The coastal line has the PZN value
of 1 and the PZN of 1.5 line cuts through the eastern edge of the study area.
Basins in the study area have PZN Values ranging fran 1.2 to 1.6.
Antecedent Hoisture Condition (AW) - me W for tho 100-year flood is
mputed based on the PZN value of the basin according to the following relation L
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mnoff curve ~unber (a) - in the SCS method for runoff estimation, the
value is used. Table I-A-1 of the Hydrology MaIIUS.1 lists the CN values related
to land use, land treabnent or practice, hydrologic condition, and soil type.
The eJ values for the AM2 of 2 are listed in the manual. Adjustment to other
AM3s is based on the information shown in Table I-A-5 of the manual.
mecipitation - The 100-year 6-hour storm and 24-hour storm are used in
this study. The precipitation in inches for each case is obtained fran the
precipitation map in the Hydrology Hanual. The values so obtained are listed
in Tables 1 and 2. Precipitation is distributed in amordance with the Type B
distribution curve. When both stom are applied in the study, the 6-hour storm
normally produces higher runoff discharges in mall basins, while the 24-hour
storm generates higher discharges for large basins. The larger of the two
discharges 50 obtained is adopted.
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Lag Time - The lag time relationship is based on criteria developed by the
U. S. Army Crops of Engineers adopted in the Hydrology Manual. Lag is defined
as the time in hours fran the center of mass of the excess rainfall to the peak
discharge, it is an enpirical expression of the physical characteristics of a
drainage area in terms of time, and is estimated as:
Lag (hours) = 24 K ----- (L *sk)m
where 75 = Basin factor, representing a measure of overall basin roughness;
m = 0.38, a constant;
L = wngth of the longest water course in miles;
Lc = Length along longest course in miles, measured upstream to the
s = overall slope, in feet par milo, of thc longest water course.
point opposite the center of area;
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L
&sin -
Al
A2
A3
A4
A5
A6
A7
A8
A9
A10
All
A12
L1
L2
L3
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Table 1. sunnary of Drainage Basin Characteristics
for Calavera Lake Creek Win
Area
eq. mi.
0.74
0.21
0.48
0.68
0.20
0.50
0.20
0.29
0.31
0.36
0.23
0.34
0.49
0.48
0.39
- PZN c
1.5
1.4
1.35
1.4
1.3
1.3
1.25
1.3
1.25
1.2
1.25
1.2
1.3
1.3
1.25
AM2 100-Yr. Rainfall, in. -
2.5
2.4
2.35
2.4
2.3
2.3
2.25
2.3
2.25
2.2
2.25
2.2
2.3
2.3
2.25
6-hr.
2.9
2.9
2.85
2.9
2.8
2.8
2.8
2.8
2.75
2.7
2.75
2.7
2.8
2.8
2.75
24-hr .
5.1
5.1
5.0
5.1
4.9
4.9
4.9
4.9
4.75
4.5
4.75
4.5
4.9
4.9
4.75
a -
90
90
89
90
87
87
88
88
90
87
86
87
86
86
86
P. 8
Lag Time
hours
0.45
0.23
0.25
0.49
0.19
0.25
0.21
0.26
0.18
0.19
0.21
0.23
0.35
0.27
0.30
Table 2. Smary of Drainage Basin Characteristics
for Aqua HeUiooda Creek Basin
PZN - Area -
sq. mi.
6.50 1.6
3.00 1.6
1.65 1.4
0.42 1.35
0.24 1.35
1.11 1.4
1.15 1.35
0.28 1.3
An: 100-Yr. Rainfall, in. - (u -
2.6
2.6
2.4
2.35
2.35
2.4
2.35 I
2.3
6-hr. 24-hr.
3.2 5.5 91
3.15 5.4 91
3.0 5.25 89
2.85 5.0 89
2.85 5.0 88
2.95 5.2 89
2.85 5.0 89
2.8 4.9 88
Lag Time
hours
1.02
0.76
0.60
0.22
0.17
0.46
0.41
0.26
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L G 0.51 1.3 2.3 2.8 4.9 87 0.38
F 0.96 1.3 2.3 2.8 4.9 91 0.17
E 0.58 1.25 2.25 2.75 4.75 86 0.23
D 0.34 1.25 2.25 2.75 4.75 86 0.16
C 0.30 1.25 2.25 2.15 4.75 90 0.12
8 0.25 1.2 2.2 2.1 4.5 87 0.24
A13 0.17 1.2 2.2 2.7 4.5 87 0.24
A14 0.43 1.2 2.2 2.7 4.5 87 0.18
A 0.28 1.2 2.2 2.1 4.5 86 0.10
________L___-_-_______________LC_____1__-----------------------------
Tatal area of two strew basins - 24.09 square miles
Calavera Lake is an important factor to stresn discharge since the lake
contributes to the attenuation of the pak discharge due to the storage of flood
weter provided by its volw. As-built plans of the dam and spillway are given
L in Fig. 1, provided by the Carlsbad Municipal water District. he spillway
consists of a broad-crested weir with a length of150 feet and a crest elevation
of 216.5 feet. A 7'4iameter standing pipe is located in the lake near the dam.
Information concerning drainage devias on tha standing pip was obtained
frm MT, Bryan Troupe of the Water District (Telephone Mmber 438-2722). only
manual devices existed before; but about five years ago, permanent drain was
installed to canply with the regulations of the California kparment of am
Safety. The permanent drain device consists of a 12-inch pipe, which is a 90
degree elbw pointing downward as shown in the figure. The drain opening 1s at
the elevation of 208.92, or 7.58 feet below the spillway crest. The downward
inlet of the drain pip is intended to avoid blockage by floating debris. Iron
bars are installed at the pip entrance to prevent large objects fran entering
the pip. The elbow pipe also has many l"-diameter holes around the surface as
additicnal drain inlets. The permanent drain maintains the lake at a level no
higher than 208.92 feetduring the normal period. According to Mr. houp, the
lake level is usually lowered a couple of feet below the elevation of 208.92
before a storm. This lowering of lake level is through a manually-controlled
drainage pipe. They have not yet &served blockage Of the permanent drainage
'id
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Sep. 3 '96 12:06 MANITOU FFIX 275 FAX 6197457487 P. 10
pipe since its installation. Access to the standing pip is provided by a boat. L
Because of the permanent drain pipe, the normal lake level should be no
In the hydrology study, the initial lake level for tk higher than 208.92 feat.
100-year storm is assured to be at the drain level.
Storage routing of flood flow through the reservoir is based on che
continuity equation for water, le.
Inflow - Oufflow Rate of lake storage
This option is included in the HEC-~ program as the modified puls routing method.
Outflow frun the lake i6 controlled at the spillway, for which the discharge
is ccmplted using the equation
where H is the head of water above the spillway crest, L is the weir length, and
C is the weir coefficient which is estimated to be 2.63 for the broad-crested
weir. In the storage routing, the elevation-surface area relation for the lake
is also employed. The tabulation for elevation-surfacre area of We lake is given
below.
L
L,
Elevation
feat
208
210
212
214
216
211
218
219
220
221
Surface Area
acres
21
24
27
30
33
35
38
39.5
I 41
43
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Results of the routing simulation for the 100-year 24-hour storm is shown
in Fig. 2. It shows the inflow hydrograph and the routed outflow hydrograph.
The peak discharge for the former is 1,803 cfs and that for the latter is 1,171
cfs. The attenuation of peak discharge is therefore 35% for the 24-hour storm.
mas attenuation is 80% for the 6 hr. storm.
There are other routing studies of the lake. A canparison of routing study
results are lis- below. However, it should be noted that earlier routing
studies were made before the installation of the permanent drain pipe. A more
conservative asswption concerning the initial lake level should be employed;
the full lake level was ass& in the earlier studies.
Nme of study Discharge of Inflow Discharge of Outflow
CfS cf s
shuinnan-Simpson, 1973 2,134 1,893
L County of san Diego
1976 2,300
This study
per 6-hr storm pr 24-hr storm 2,347 1,803
9 00
477 1,171
The discrepancy in results may also be attributed to the type of stonn used.
Such information for other studies could not be obtained to make a canparison.
IV. RESULTS OF HYDROLCGY STUDY
Results of the hydrology study are smrized in Table 3. Oihhsr detailed
output information can be found fran the cmputeer listings of HEC-1 in Appendix
A. For the 6-hr, and 24-hr. storms, only the higher of two discharges is listed.
It can be seen that the 6-hs. storm produces higher discharges in analler basins
while the 24-hr. stonn generates higher values for larger basins, This procedure
was not followed by all previoun studies.
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Table 3. S-ry of Peak Discharges for the 100-Year Flood
Pt. of Con Drainage Area 6-hr Stom 24-hr storm -cent ration Lcxa t i on ' in square miles e in cfs
1
2
3
4
5
5
6
7
8
8
8
10
1 11
Calavera Lake Creek at exit of Basins Al and A2
Calavera Lake Creek at Exit of Basins A3 and A4
Calavera Lake Creek at Exit of Basins A5 and A6
Calavera Lake Creek at eas- tern end of Calavera Lake
Calavera Lake Creek just
upstream of Calavera Dam
Calavera Lake Creek just dwmtream of Calavera Dm
Calavera Lake Creek at exit of Basins A10 and All
Calavera taka Creek at
Exit of Basins L1 and ~2
East Branch of Calavera Lake
Creek just before entrance of mobile hane park
Calavera Lake Creek just
before entrance of mobile hame park
Calavera Lake Creek at entrance of mobile haw park, cmbined flow froln
north and east
Aqua Hedionda Creek just downstrcmn of conflueme with mna Creek at Green Oak Ranch
Aqua Hedionda Creek at exit of msins uE, up and ffi near City limit
Aqua Hejfonda Crnk at exit
of Basins uc and UD
8
0.95 674
2.11 1.445
2.81 1,850
3.30 2,155
3.61 2,341 1,803
3.61 1,171
4.20 1,236
0.97
1.36
4.54
5.90
9.50
12.0
2.07
614
811
1,353
1,739
5,299
5,962
1.231
Sep. 3 '96 12:07 MANITOU FAX 275
14 Aqua Hedionda Creek at exit of Basin H
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2.42
12 Aqua Hedionda Creek just
downrtrean of confluence
with unnamed tributary 15.89
15 Aqua Hedionda creek at
300' upstream fran Rancho
Carlsbad 16.47
17 Aqua Hedionda Creek at 130' upstream fran Rancho
Carlsbed 17.05
18 Aqua Hedionda Creek just upstrean of confluence
with Calavera take Creek 17.30
18 Aqua HEdandS Creek just downstrean of confluence with Calavera Lake Creek 23.80
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19 Aqua Hedionda Creek just downstream of El Camino Real Bridge 24.09
P. 13
1,383
7,597
7,809
7,997
8,080
9,848
9,910
The discharges obtained in this study are canpard with those given in
previous studies. The canparison is listed in Table 4. It is important to
ranenber, again, that discharges obtained in this study are affected by the
drain modification in Lake Calavera around 1985, and this condition did not exist
when earlier studies Were made. In the Rick study of 1983, the storage effect
of Calavera Dam was not considered since the flood flow was not routed through
the lake.
Table 4, Canparison of Peak Discharges for 100-Year Flood
Point Area This Study Rick County Corps Vista - conc . Location sq. mi. - 1989 - 1983 - 1976 1973 1979
I 5 Calavera Lake Creek just
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upstseam of Calavers an 3.61 2,347 2,300
downstrean of Calavera ran 3.61 1,171 900 L 5 Calavera Lake Creek just
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8 Calavera rake Creek at entrance of mobile bane
prk, canbined flow fran
10 Aqua Hedionda Creek just downstrean of confluence
with Bwna Creek at
north and east 5.90 1,739 3,512 1,400
Green Oak Ranch 9.50 5,299 5,621 7,000 6,900 5,035
11 Aqua HedlOnd.3 Creek
12 Aqua Hedionda Creek ju6t downstream of confluence
with unnamed tributary 15.58 7,462 7.700 7,900
18 Aqua Hedionda Creek just
near Carlsbad city limit 12.00 5,962 7,200
upstream of confluence
with Calavera Lake Creek 17.30 8,080 9,965 7,900
18 Aqda Hedimda Creek just downstream of confluence with Calavera Lake Creek 23.80 9,848 13,472 10,000 10,300
V. EUXD PLAIN STUDY FOR MOBILE HDME PARK L
The scope of the flood plain study cover8 Aqua Hedionda Cteek fran the
bridge at El CBnino Real to the eastern boundary of Rancho Carlsbad Mobile Haw
Park (Rancho Carlsbad Drive). The purpose of the study is to deteiminc the flood
level and flood plain boundary of Aqua Hedionda Creek for the discharges obtained
in this study. cross-sectional profiles for Aqua Hedionda Creek are given in
Figs. 3 to 20.
The through the mobile hane park has been silted in
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eteminod to be 2.5 feet fran the surveyed
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'+ .
The flood plain rtudy is on the assunption that channel inprovenent Items
The cangut4 water-surfam profile Calavera described herein are implemented.
Lake Creek is shown in Fig. 21.
Flood plain studies for Aqua Hedionda Creek have been made by Rick
Engineering, 1983; ic covers the creek fran the coastal lagoon through Rancho
Carlsbad Mobile Hane Park and Rancho Carlsbad Golf Course. Previous cross
sections are used in this study but they are updated to reflect recent changes.
Since the canpletion of the Rick Engineering study, the bridge at Runcho carlsbad
Drive has been modified. The new configuration is us& in this study. he
present bridge has triple box culverts. The width of each box is 12 feet and
the height varies fran about 12 feet to 10 feet, reflecting the uneven bed
profile.
This study has been made using the HE2 canplter model developed by the
U. S. Amy Crops of mgineers. Ineffective flow areas in the flood plain are
specified using the Fl' or X3 records. The input and output listings are
suhnitted with the report (see Appendix 81, together with a map showing the cross
section locations and flood plain boundary (see Attachnent) . The plotted results
include the cross-section profiles, channel-be8 profile, and water-surface
profile.
The Rancho Carlsbad Drive Bridge on Aqua Hedionda Creek is insufficient to
pass the 100-year flood, with a portion of the flow overtopping the bridge
roadway. The overtopped flow will spread to the mbile hane park downstrean to
km perched flow for the flood plain. The boundary affected by the perched
flow is not sham in the map.
On the basis of the study results, certain recannendations are made in order
to improve the current drainage condition though the mbile hone park. The
current shallow channel of Calavera rake Creek is insufficient to pass the design
flood discharge of 1,740 cfs. L.: i
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L 1. Restoration of the 3 e@ through the mobile hone park by mqi The design dimmy be acrarmodated by a proper
channel improvement within the physical constraint of 40-foot surface width. m
adequate channel configuration is given in the previous section. The channel
boundary needs to be protected against the pmk velocity of about 10 feet pee
second. Protection of the channel boundary may ba achieved by using such
materials as armorflex or geoveb.
Creek frG the Calavera Lake Creek confluence to El Mino Real Bridge by 2.5
feet.
,,,. . ,*.. rii..'
~ w.L.Ui.rr 3. Future siltation of the channel may be prevented by-
installed upstrem of the mobile hane park. llro such facilities are recmnded,
with one on the north channel branch and one on the east branch.
4. The Rancho Carlsbad Bridge on Aqua Hedionda Creek iS insufficient to pass
the 100-year flocd of about 8,000 cfs, With a portion the flow overtopping the
bridge roadway. The overtopped flow will spread to the downstream to becune
prched flow for the downstrean flood plain. This situation may be improvement
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REFEREIEES
1. "Calavera Dam Inundation Study, City Of Carlsbad", Shuirman-Simpson Consulting Engineers, September 1973.
2. "Flood Plain Information, Aqua Hedionda Creek", Deparment of the Army, Los Angeles District, Corps of Engineers, July 1973.
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3. "Aqua Hedionda Creek", County of san Diego, 1976.
4. "Drainage Master Plan, City of vista", L C S Consultants, San Marcos, CA, 1978.
5.
JW, 1983.
6.
"Rancho Carlsbad Drainage and Flood Plain Study", Rick Engineering Canpany,
"Hydrology Manual", County of San Diego, January 1985.
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