HomeMy WebLinkAboutCT 75-04; La Costa Estates North; Hydrology Study; 1988-10-12FRASER
ENGINEERING, INC.
SITE HYDROLOGY STUDY
TERNYILA RESIDENCE
I-& Cosk Gr_Sk++77 W0vtl-h
Job No. 605-01-01
Prepared
October 12, 1988
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City of Carlsbad
Engineering Department
ENGINEERING DEPT. LIBRARY
City of Carlsbad 2075 Las Palrnas Drive Carlsbad, CA 92009-4859
FRABER ENQINEERINQ, INC.
FRASER
ENQINEERZNQ. INC.
FRASER ENGINEERING. INC.
d/ll &?A
SAN DIECO. CALIFORNIA 92123
TELEPHC.XE: 16191 565.5177
February 19, 1985
TO : Users of the San Diego County Hydrology Manual and
Design and Procedure Manual
FROM: R. J. Massman, Director, Department of Public Norks
SUBJECT: Replacement of Intensity-Duration-Frequency Curves
The old Intensity-Duration-Frequency (I-D-F) Curves in the County Hydrology Manual
and Design and Procedural Manual are being replaced with the new Intensity-Durdfiorb Design (I-D-D) Chart.
The reasons for this change are as follows: ... -.
.. ,.
1. The old I-D-F Curves (developed in about 1965) were based on extremely
limited data from the San Diego National Weather Service (ZnrS) and
the Mount Laguna rain gauges.
2. The new I-D-D Chart is based on up-to-date precipitation data and
statistical analysis which makes the results much more reliable and
consistent with Federal and State studies and reports.
3. The I-D-D Chart is applicable for the rational method in small dra5.n- age basins and used the NWS isopluvial maps, which reflect orographic
effects for rainfall amounts. The hydrology procedures for larger basins also use the isopluvial maps which provides better consisteocy between the two methods.
4. The I-D-D Chart can be used for computer applications with the eyuz-
tion relating precipitation and duration to intensity.
In summary. the new I-D-D Chart provides an engineering basis for analysis and design consistent with Federal, State and local data, methods and reports.
p. J. bLGShL4N. Director
Department of Public Works
RJ>l:KH:seb Enclosures: 1. New Intensity-Duration-Design Chart
2. Two Sample Computation Sheets
r W
cr
L 0 v-
W > L a u
0 c,
c W
c 0
m
01 aJ
v c c m L m Q
c 0 .-
c, L W VI
c3 W
c, 0
c, E c
0 n
.. .
r W
U
c m a a
c
n
V c,
I
10 I
Y
A rl A d n Ln
6-Hour Precipitation (inches) .. ..
ov)ovIouJ 0 In 0 In n
.. -
7ho , "I n
rc
HIGHWAY DESIGN MANUAL 810-11
January, 1087
Figure 816.6A
Overland Time of Concentration Curves
I- W W u.
Z -
w'
a
n 2
0 z
c
-I W > a a I-
O z
A
W > 0
a
a
1000
800
600
400
200
0
80
60
40
20
0
v) W I- 3 1 z z
A-
a a
-
W >
I-
LL 0
W
I-
z
-I
W
0 >
2
n
a
a
Where:
C = Runoff Coefficient
L = Overland Travel
Distance in feet
S = Slope in ft./ft.
To = Time in minutes