HomeMy WebLinkAboutCT 81-16; VISTA SANTA FE; DRAINAGE STUDY; 1981-04-21VISTA SANTA FE
DRAINAGE STUDY
PREPARED FoR
RICK ENGINEERING COMPANY
APRIL 21, 1981
LEEDS, HILL AND JEWETT, INC
1275 MARKET STREET
SAN FRANCISCO, CA 94103
TELEPHONE (415) 626-2070
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LEEDS, HILL AND JEWETT,INC,
II. THE STUDY AREA
The study area of this report is about 1,400 acres in
size. About 230 acres of the study area are outside the boundaries of
Vis ta Santa Fe development but contribute runoff to the development.
The location and boundaries of the study area are shown on Figure 1.
Existing Conditions
Data on existing conditions at the study area are avaiLable
from u. S. Geological Survey topographic maps and from large scale
topographic maps prepared by Rick Engineering Company. Soil and
ground cover data for the area are available from maps prepared by the
County of San Diego. In addition to these sources of data, informa-
tion obtained during field inspections of the study area and aerial
photographs of existing conditions are available.
Most of the 1,400 acre study area is in a natural condition,
undisturbed by man's activities. The terrain of the study area is
rolling hills that have moderate to steep-slopes. Natural vegetation
in the area consists mainly of annual grass and open brush. Soils in
the area are classified primarily as being in hydrologic soil group B
that has infiltration rates of up to 0.05 inches per hour. The area
is drained by two streams: Encinitas Creek that flows from east to
west through the southern portion of the study area and; an unnamed
stream that flows from northeast to southwest through the northern
portion of the study area and joins Encinitas Creek downstream of the
study area. The streams have steep slopes at their headwaters and
mild slopes near the confluence of the two streams. The stream
channels are fairly well incised and contain brush.
The only major road that traverses
Rancho Santa Fe. A minor portion of the study
the
area,
study area is
located on the
west side of Rancho Santa Fe road about one mile north of Olivenhain
Road, is currently developed in residential use.
4
TABLE 2
HYDROLOGIC CHARACTERISTICS FOR EXISTING CONDITIONS
Mean Lag 2/ Percent
Area Slope Rou.9.hness Time Area
Subarea (acres) (ft/mi.) n 1./ (minutes) Developed
I 914 125 . 07 58 0
II 406 235 .08 34 0
III 61.2 35 .08 38 0
1/ Mean Manning's Roughness Coefficient.
2/ Time between the beginning of excess rainfall and the centroid
of runoff.
scs
Curve
No .
80
83
84
Subarea
I
II
III
II & III
I, II & III
TABLE 3
PEAK DISCHARGE RATES AND RUNOFF VOLUMES AT SUBAREA
OUTLETS FOR EXISTING CONDITIONS
10-Year Storm 25-Year Storm
Peak Rate Volume Peak Rate Volume
(cfs} (acre-feet) (cfs} (acre-feet}
78 23.6 143 39.9
59 13.6 107 21.8
10 2.2 17 3.6
68 15.8 122 25.4
136 39.4 246 65.3
TABLE 4
HYDROLOGIC CHARACTERISTICS FOR FUTURE LAND.USE CONDITIONS
Mean Lag ·Percent scs
Area Slope Rou.9.hness Time ?:_I Area Curve
Subarea (acres) (ft/mi.) n .Y (minutes) Developed No.
1 20.6 265 .030 8.1 100 88
2 54.8 685 .030 9.1 100 89
3 40.7 690 .080 6.3 0 84
4 18.2 1530 .130 7.3 0 84
5 56.7 90 .090 21.8 0 84
6 17.6 145 .040 6.8 100 90
7 17.2 210 .045 6.9 100 89
8 12.3 510 .070 6.2 0 84
9 107.1 165 .030 9.1 100 89
10 41.5 320 .080 8.3 0 84
11 23.8 560 .080 5.6 0 84
12 86.5 215 .100 7.7 0 85
13 24.1 105 .045 3.6 100 89
14 35.7 435 .055 6.5 100 89
15 9.0 200 .050 3.6 100 89
16 34.8 225 .040 5.5 100 90
17 33.3 165 .100 16.7 0 84
18 7.9 390 .100 4.2 0 84
19 27.0 250 .040 5.8 100 90
20 47.0 355 .050 7.2 100 89
21 27.2 780 .045 7.0 100 89
22 32.3 542 .035 7.6 100 90
23 45.8 115 .050 10.5 0 83
24 18.2 120 .040 6.1 100 89
25 7.6 250 .075 5.1 100 89
26 15.3 135 .045 6.7 100 88
27 35.7 120 .035 6.6 100 89
28 29.8 105 .035 6.5 100 89
29 14.3 75 .070 11.1 0 80
30 5.7 105 .015 3.3 100 91
31 29.7 420 .040 7.2 100 89
32 50.6 240 .035 8.9 100 89
33 190.4 415 .060 17.4 0 84
34 51.7 110 .040 8.4 100 89
35 89.4 llO .120 28.4 100 82
36 8.6 200 .060 6.4 100 89
37 57.0 325 .045 10.8 100 88
38 14.5 405 .130 6.5 0 83
39 21.2 240 .055 5.5 100 -89
1/ Manning's mean roughness coefficient.
~/ Time between the beginning of excess rainfall and the centroil
of runoff.
TABLE 5
PEAK DISCHARGE RATES AND RUNOFF VOLUMES AT SUBAREA
OUTLETS FOR FUTURE LAND USE CONDITIONS
WITHOUT DRAINAGE CONTROLS
10-Year Storm 25-Year Storm
Peak Rate Volume Peak Rate Volume
Subarea (cfs) (acre-feet) (cfs) (acre-feet)
1 10 1.1 16 1. 6
2 28 3.1 45 4.6
3 12 1.5 21 2.3
4 5 0.6 9 1.0
5 11 2.1 20 3,3
6 13 1.2 19 1. 7
7 9 LO 14 1.3
8 3 0.4 6 0.6
9 53 5.7 84 8,3
10 11 1.4 19 2.2
11 7 0.8 12 1.3
12 17 3.3 31 5.2
13 14 1.4 22 2.1
14 21 2.0 33 3.0
15 5 0.5 9 0.7
16 24 2.1 37 3.1
17 7 1.1 13 1.8
18 2 0.3 4 0.4
19 17 1. 6 26 2,2
20 26 2.7 42 3.9
21 16 1.6 25 2.3
22 22 2.1 33 3.0
23 11 1.5 20 2.5
24 11 1.0 17 1.5
25 5 0.5 7 0.6
26 8 0.8 13 1.2
27 21 2.0 33 3.0
28 17 1.7 28 2.5
29 2 0.3 4 0.5
30 5 0.5 8 0.6
31 17 1.7 26 2,5
32 27 2.9 43 4.2
A 320 50.6 536 75.4
33 42 6.9 76 11.0
34 30 3.1 47 4,5
35 12 2.7 23 4.5
36 5 0,5 8 0,7
37 26 3,0 42 4.5
38 4 0.5 7 0.8
39 13 1.2 20 1.8
B 101 18.0 172 27.8
A+ B 420 68.6 706 103.1
TABLE 6
RUNOFF CHARACTERISTICS WITH THE DRAINAGE CONTROL PLAN
10-Year Storm 25-Year Storm 100-Year Storm
Peak Outflow Peak Outflow Maximum Water Storage Characteristics
cfs cfs Water
Existing Future Future Existing Future Future Water Surface
Land Without With Land Without With Depth Freeboard Storage Area
Location Use Basins Basins Use Basins Basins (feet) (feet) ( acre-feet) (acres)
A 78 320 78 143 536 150 12.2 0.6 52 8.5
B 68 101 47 122 172 79 10.3 1.9 15 4.2
A & B 136 420 124 246 706 221