HomeMy WebLinkAbout; Agua Hedionda Creek; Hydrology Report; 1976-12-01.. . i
'"COUNTY OF SAN DIEGO
COMMUNITY SERVICES AGENCY
SFC 3756
Department of Sanitation 6, Flood Control
TABLE OF COmENTS
I. INTRODUCTION
A. Authorization
C. Prior Reports
B. Scope and Purpose
D. Acknowledgements
11. CONCLUSIONS AND RECOMMENDATIONS
111. WATERSHED CHARACTERISTICS
A. Geographic Description
C. Soil Groups
B. Vegetation
D. Structures
IV. HYDROLOGIC COMPUTATIONS
A. Summary of Methods Applied
B. Basis of Computations
BIBLIOGRAPHY
GLOSSARY
2
3
10
11
ENGINEERING DEPT. LIBRARY
City of Carlsbad 2075 Las Palmas Drive Carlsbad CA 92009-4859
TABLES
Table 1
Table 2
Table 3
Table 4
Table 5
Peak Flood Flows for Flood Plain Mapping
Comparison of computed Flood Flows
Percent of Land Use by Soil Groups for
Entire Basin
Percent of Soil Groups by Sub-Basin
Lag Time and Time to Peak Determination
Page
4
6
7
-
8
9
Plate 1
Plate 2
PLATES
Study area map with concentration
points and sub-basin boundary
delineations
Cubic feet per. second per square
mile versus drainage area
enveloping curve
AGUA HEDIONDA CREEK
I. INTRODUCTION
A.
B.
C.
D.
Authorization
The Board of Supervisors of San Diego County has authorized County
Agua Hedionda Creek.
General Funds for this Department to perform Flood Plain Mapping on
Scope and Purpose
This report documents the processes used to develop present flood
of the Agua Hedionda Creek watershed for use in Flood Plain Mapping.
flow rates from rainfall data and watershed runoff characteristics
Prior Reports
The U.S. Army Corps of Engineers, September 1972 (Ref. 1) and July 1973
Previous hydrology studies on Agua Hedionda Creek were published by:
(Ref. Z), for flood plain information; the firm of Shuirman and Simpson, for the Master Drainage Plan Phase I, City of Carlsbad,
April 1971 (Ref. 3), and the same firm for the Calavera Dam Inundation
Study, City of Carlsbad, September 1973 (Ref. 4).
Acknowledgements
The National Weather Service (NWS) provided rainfall data used in the
analysis (Ref. 5).
The U.S. Soil Conservation Service (SCS) provided soil group and ground
cover maps.
11. CONCLUSIONS AND RECOMMENDATIONS
The peak flows listed in Table 1 will be used in the Flood Plain Mapping
of Agua Hedionda Creek. These 100-year frequency peak flows are within 10%
of both the flows computed in this analysis and those listed in the Corps
See Table 2.
of Engineers' reports, while the 10-year frequency flows are within 25%,
111. WATERSHED CHARACTERISTICS
A. Geographic Description
Agua Hedionda Creek originates in the San Marcos Mountains and flows
-1-
westerly into Aqua Hedionda Lagoon which empties into the Pacific Ocean.
The entire watershed lies within the County of San Diego and includes
The Agua Hedionda Creek watershed is long and narrow in shape, with a parts of the cities of San Marcos, Carlsbad, and Oceanside (Plate 1).
distance of about 13 miles from the ocean to the highest mountain peak
and an average width of about 3 miles. Total area for the watershed is
about 30 square miles. Elevations range from Mean Sea Level (M.S.L.)
at the Pacific Ocean to about 1,700 feet. Average slope is about 130
feet per mile.
The Flood Plain Mapping will be in two parts, a downstream and an
upstream as follows:
1. Downstream - Limits are from the entrance of Agua Hedionda
Lagoon to about 3,500 feet upstream from El Camino Real.
2. Upstream - Limits are from the confluence of Agua Hedionda and
Buena Creeks to Ora Ava Drive (Buena Creek Tributary). Also,
limits are from the confluence of Agua Hedionda Creek and Buena Creek
to the Atchison, Topeka and Santa Fe Railway (Agua Hedionda Creek).
B. Vegetation
Annual grasses dominate the coastal lowlands, while vegetation in the
upper areas consist mainly of annual grasses and open brush, with some
broadleaf and narrowleaf chapparal in the San Marcos Mountains and
citrus and avocado orchards in the low hills.
C. Soil Groups
Soil particle sizes increase from fine sands and silts at the coast
and low gradient reaches to decomposed granite with clay content as
A and B, with the remaining 75% containing Soil Groups C and D. Group
one moves inland. 25% of the total area is composed of Soil Groups
A soils are concentrated at the coastal lowlands while Group B soils
are in the upper reaches.
D. Structures
Except for the Atchison, Topeka, and Santa Fe Railway bridge within
were considered not effective in reducing peak flows due to floodwater
the lagoon area and the Calavera Dam, structures within the watershed
storage.
IV. HYDROLOGIC COMPUTATIONS
A. Summary of Methods Applied
A modified Soil Conservation Service (SCS) rainfall-runoff method, as
described in the San Diego County Hydrology Manual (Ref. 6) was used
to determine the flood flow rates. The SCS dimensionless unit hydro-
graph with a K value of 484 was used for all calculations.
ENGINEERING OEPT. LIBRARY
City of CarIsW 2075 Las Palmas Oriw CarlsbaQ CA 92009-4859
B. Basis of Computations
The computed peak flows in this study are based upon current land
use and reflect existing (1976) conditions.
The Calavera Dam reservoir filling frequency was not determined;
however, the storage capacity of about 1650 acre-feet is small
(Ref. 4, pg. 5). Therefore, the reservoir was assumed full prior
used to add the discharge from Calavera Dam (C.P. 19) to the down-
to routing the 100-year frequency flood (C.P.1S). The travel times
pendent upon the reach slopes; from 10 feet per second for steep
stream concentration points were calculated by assuming velocities de-
sections to 5 feet per second for mild sections. In the studies
by the U.S. Corps of Engineers, the flow at Sycamore Avenue and
Highway 78 (C.P.Y) was assumed controlled by the culvert beneath
Highway 78. Field inspection indicated that excess flood waters
would bypass the inlet and proceed down Sycamore Avenue to meet
with the culvert outflow just downstream of Highway 78 with negligible
reduction in the peak flow.
The flow at the Atchison, Topeka and Santa Fe Railway Bridge in the
lagoon area (C.P. 24 & 25) was routed to determine the effects of
flood water storage. Stage-discharge-area relationships used to
by Mr. Joseph Hill of this department in 1972 based upon topography
construct the rating curves for computer program input were approximated
maps furnished by the City of Carlsbad and A.T.G S.F. bridge
drawings.
.
-3-
Concen-
Point No. tration
1
4
5,6
7
8,9
10
11
12
13
14
TABLE 1
AGUA HEDIONDA CREEK
PEAK FLOOD FLOWS FOR FLOOD PLAIN MAPPING
Locat ion
Drive just upstream of
Unnamed tributary near Canyon
confluence with Buena Creek
Buena Creek just upstream of
Ora Ava Dr.
Buena Creek just upstream of
confluence with unnamed tri-
butary near Canyon Dr.
stream of Canyon Dr.
Buena Creek just down-
Buena Creek at Highway 78
Buena Creek just upstream
Hedionda Creek
of confluence with Agua
Agua Hedionda Creek at
Highway 78
downstream of Highway 78
Agua Hedionda Creek just
Agua Hedionda Creek just
upstream of confluence with
Buena Creek
Agua Hedionda Creek just
downstream of confluence
with Buena Creek at
Green Oaks Ranch
Agua Hedionda Creek 1.33 miles
downstream of Green Oak Ranch
Agua Iledionda Creek just
upstream of confluence with
unnamed tributary at
elevation 200
DRAINAGE
AREA SQ.MI.
0.9
1.6
2.3
3.1
5.1
6.5
2.0
2.1
3.0
9.4
11.6
12.5
DISCHARGE DISCHARGE C.F.S. C.F.S.
1,000 250
100-YEAR 10-YEAR
2,000 550
2,500 600
3,300 700
4,900 1,200
5,000 1,200
2,100 400
2,100 400
2,700 550
7,000 1,600
7,200 1,700
7,200 1,700
-4-
Concen-
tration
Point No.
15
16
17
18
19
20
21
22
23
24
25
TABLE 1 (Cont'd
AGUA HEDIONDA CREEK
PEAK FLOOD FLOWS FOR FLOOD PLAIN MAPPING
Location
Unnamed tributary at
elevation 200 just upstream
of confluence with Agua
Hedionda Creek
Agua Hedionda Creek just
downstream of confluence
with unnamed tributary
Agua Hedionda Creek just
upstream of Calavera Dam
tributary
Calavera Dam tributary
just upstream of reservoir
Calavera Dam tributaary
just downstream of reservoir
Calavera Dam tributary
just upstream of confluence
with Agua Hedionda Creek
Agua Hedionda Creek just
downstream of confluence
with Calavera Dam tributary
Agua Hedionda Creek 1.35 miles downstream of con-
fluence with Calavera Dam
tributary
Agua Hedionda Creek at
entrance to lagoon
Agua Hedionda Creek total
inflow into lagoon
Agua Hedionda Creek just
downstream of A.T.S.F. R.R.
Bridge
DRAINAGE
AREA DISCHARGE DISCHARGE
100-YEAR 10-YEAR
SQ.MI. C.F.S. C.F.S.
3.3 1,800 350
15.8
17.6
3.7
3.7
5.8
23.4
24.7
27.9
30.3
30.3
7,700 1,900
7,900 1,900
2,300 550
900 250
1,400 300
10,000 2,100
10,000 2,100
10,500 2,100
10,500 2,100
7,000 1,100
-5-
Area
sq. mi.
0.9
2.3
1.6
2.9
3.1
5.1
6.3
6.5
1.9
2.0
2.1
2.8
3.0
9.1
11.4
9.4
11.6
12.5
15.3 3.3
15.8
17.6
3.7 inflow
Conc .
Point
1
2
3
4
596
7
899 10
11
12
13
14
15
17
16
18
-
TABLE 2
AGUA HEDIONDA CREEK
COMPARISON OF COMPUTED FLOOD FLOWS
COUNTY 1976 CORPS 1973 F.P.I. STUDY
Q 100 Q 100
Flood
Flow
Flood
cfs/ Conc. Flow CfS/
cfs sq. mi. Point cfs sq.mi.
1,000
2,000
1,111
2,500
1,250
1,087
3,300
4.900
1,065
96 1
5,300 815
2,100
2,100
1,000
1,050
- - -
2,600 867
7,600 809
7,500 647
6,900 552
1,800 545
7,900 500
7,900 449
2.300** 630
3.7 outflow 19 900 243
5.8 20 1,400 241
23.3
23.4 21 9,400 402
24.7 22 9,400 38 1
27.9 23 10,500 376
30.3 24 10,500 347
25 7,000 231
**Calaveras Lake assumed full
*Culvert outflow
11
9- B
10
9-A
9
8
7
3,300 1,138
4,800 761
1,100* 579
2,700 964
6,800 747
7,000 614
7,700 503
10,300 442
10,500 376
TABLE 3
AGUA HEDIONDA CREEK
PERCENT OF LAND USE BY SOIL GROUPS FOR ENTIRE BASIN
Land Use
Row Crops contoured
Water
Orchards Evergreen
Orchards Evergreen
Urban Low Density
Urban Medium Density
Annual Grass
Annual Grass
Broadleaf Chaparral
Broadleaf Chaparral Narrowleaf Chaparral
Narrowleaf Chaparral
Open Brush
Open Brush
Woodland Grass
Woodland Grass
Turf
Woods (Woodland)
Hydrologic
Condition
Poor
Good
Fair
Poor
Fair
Fair
Good
Good
Fair
Fair
Fair
Poor
Good
Good
Fair
Fair
Poor
Good
2.9
0.5
0.0
0.0
1.6
3.3
0.0
0.7
0.0
0.0
0.0
0.0
0.0
0.2
0.0
0.0
0.0
0.0
9.2
-
2.2
0.0
0.0
0.0
1.6
0.0
0.2
1.5
1.7
0.2
0.0
0.0
0.0
6.4
0.0
0.0
0.0
0.0
13.8
-
Soil Groups by Percent
A B C D
2.3
0.2
2.8
1.0
2.6
0.2
0.1 5.5
0.5
0.7
0.0
0.0
3.1
0.2
0.0
0.2
0.0
0.0
19.4
-
10.3
2.3
3.0
0.3
5.7
2.3
13.1
3.1
2.1
3.0
1.5
0.6
7.6
1.9
0.2
0.2
0.1
0.1
57.4
-
-7-
BAS IN
POINT -
1
2
3
4
6
7
10
11
12
13
14
15
16
17
18
20 21
22
23
24
AMC
1
64
66
64
64
64
66
66
66
64
66
63
63
63
63
68
63
64
64
64
63
-
TABLE 4
AGUA HEDIONDA CREEK
PERCENT OF SOIL GROUPS BY SUB-BASIN
AMC
2
82
81
81
81
82
81
82
82
81
82
80
80
80
80
84
80
81
81
80
81
- AMC
3
92
92
92
92
92
92
92
92
92
92
91
91
91
91
93
91
92
92
92
91
- SQ.MI . AREA
0.9
1.6
2.3
3.1
6.5
5.1
2.1
3.0
11.6
9.4
12.5
3.3
15.8
17.6
3.7
2.1
24.7
23.4
27.9
30.3
A B C D
SOIL GROUPS BY PERCENT
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.9
9.2
12.5
0.0
0.0
3.5
9.9
8.9
0.0
0.0
13.9
6.1
19.8
28.6
21.6
21.2
12.1
5.8
18.0
17.3
15.6
13.9
25.0
25.0
36.1
32.9
34.0
36.1
21.1
19.5
30.9
27.9
26.2
2.2
20.4
21.2
15.5
39.7
21.4
21.2
21.1
19.5
62.5
75.0
63.9
63.5
56.0
55.0
78.9
80.5
63.0
58.2
54.0
69.2
57.2
58.4
78.6
48.3
60.7
61.5
61.3
57.5
MINI" INFIL-
TRATION IN./HR.
0.019
0.013
0.018
0.018
0.022
0.023
0.011
0.010
0.019
0.021
0.023
0.015
0.021
0.021
0.011
0.026
0.020
0.019
0.020
0.026
mmm~m~m~mmmmm~mmm~m~m MMMMMMMMMMMMMMMMMMMMM CI 000000000000000000000 dddddddddddddoooooooo ........
as I
0
momm~bbt~~mmmm~bNommh
o~oooooooommhmwo~mmmh mmmmmmmmmmmmmmmmmmmmm
..................... m 3
k
?-V m3mmhbbu~M33mhbo~MNoo mmmmmmmmmmmm~~hh~hhhh 23 NNNNNNNNNNNNNNNNNNNNN 0 3
.3
x e
a .....................
E 8 c,
a al
a
c, 0
BIBLIOGRAPHY
- 1. "Hydrology for Flood Plain Information, Buena Vista and Agua Hedionda
Creeks", U.S. Corps of Engineers, September 1972.
2. "Flood Plain Information, Agua Hedionda Creek", U.S. Corps of
Engineers, July 1973.
3. "City of Carlsbad Master Drainage Plan, Phase I", Shuirman-Simpson
Consulting Civil Engineers, April 1971.
-4. "Calavera Dam Inundation Study, City of Carlsbad", Shuirman-Simpson
Consulting Civil Engineers, September 1973.
5. "Precipitation-Frequency Atlas of the Western United States, Volume XI
California", NOAA Atlas 2, National Weather Service, National Oceanic
and Atmospheric Administration, U.S. Department of Commerce, 1973.
6. "Hydrology Manual", County of San Diego, Department of Sanitation and
Flood Control, October 1973 (revised November 1975).
-10-
" GLOSSARY OF TERMS FOR RAINFALL-RUNOFF ANALYSIS
"
The following glossary of terms is presented in simplified form and may not
reflect exact engineering definitions.
antecedent moisture condition (AMC) -- The degree of wetness of a watershed - at the beginning of a storm.
- on the soil surface (also includes pavement, houses and buildings in urban areas).
cover -- The vegetation, or vegetational debris such as mulch, that exists
hydrologic condition -- Relative amount of cover.
hydrologic soil group -- A group of soils having the same runoff potential
under similar storm and cover conditions.
-
-
runoff curve number (CN) (hydrologic soil-cover complex) -- A combination of
runoff.
a hydrologic soil group and a type of cover used in quantifying the amount of
hydrograph -- A graph showing the discharge, stage, velocity or other property
of water with respect to time for a given point on a stream.
unit hydrograph -- A discharge hydrograph coming from 1 inch of direct runoff
a uniform rate during the given storm duration.
distributed uniformly over the watershed, with the direct runoff generated at
K-value -- A constant reflecting both the conversion of units and the shape of
the unit hydrograph.
basin factor (K) -- The measure of resistance to flow in all the channels within
a drainage basin.
time to peak (Tp) -- The length of delay between the time rain falls and the
corresponding runoff.
-1 1 -