�~�~ WALSH ENGINEERING~r~r& SURVEYING, INC.

CEQA PRELIMINARY DRAINAGE STUDYFor

Montemar EstatesAPN 504-242-41

TM 5316

Date

Prepared for:

~~@~D\Yl~ ill)MAR 0 72006

Distinctive Homes707 Broadway, Suite 1150

San Diego, CA 92101

San Diego County(Walsh Engineering Job No 02329) DEPT. OFPLANNING & LAND USE

1870 Cordell Court, Suite 102· EI Cajon CA92020· Phone (619) 588-6747· Fax (619) 448-7132........ , ••• ""I ....h .....""-..: .....,.................... _

INTRODUCTION

This Drainage Study is prepared for TM 5316, a major subdivision proposing 13 half-acre lots.The site is located on the south side of Monte mar Drive west of Austin Drive in Spring Valley.See the attached Vicinity Map.

1. Existing Conditions, Basins and Drainage Facilities

There is one existing drainage basin (Basin A) contributing to the project. Basin A is 41.6 acresin size and contributes 54.8 cfs, during the 100-year storm, to the existing swale in the southeastcomer of the project at the southerly boundary. See the attached Drainage Map I and DrainageBasin Calculations.

There is an existing 18" eMP storm-drain pipe underneath Montemar Drive in the northwestcomer of the project. BasinB contributes 6.26cfs during the 100-year storm to the existing pipe,which then flows onto the project. See the attached Drainage Map I and Drainage Calculations.

2. Proposed Conditions, Basins and Drainage Facilities

In the proposed condition, the runoff coefficient for Basin A will change due to the proposeddevelopment. Subsequently, there is a 0.4 cfs increase in peak runoff when measured at the"Point of Comparison". The "Point of Comparison" is the point at which Basin A is concentratedin the existing swale and the runoff exits the project. See the attached Drainage Map 2 andDrainage Calculations.

The proposed drainage facilities will have rip rap outlet protection / velocity reduction. Eachdrainage system will be outlet into vegetated swales, which return the runoff to the existingswale in the southeast comer of the proposed subdivision. The proposed storm-drain systems areanalyzed herein. See the attached Drainage Map 2 and 3 and Drainage Calculations. Thisdrainage study determined the proposed facilities to have adequate capacity during the 100-yearstorm event.

All of the proposed drainage facilities will outlet the stormwater runoff into existing swalesbefore leaving the project boundary. The overall drainage characteristics for this project willultimately remain unchanged.

3. Pre-Development vs. Post-Development

The peak runoff rates for the pre-development and post-development conditions have beenanalyzed herein. This study has determined a 0.4 cfs increase in peak runoff due to the proposeddevelopment, which equates to a 0.7% increase from the existing condition. The increase isconsidered insignificant and the proposed development will have no adverse impacts, since thepeak runoff rates and velocities will virtually remain unchanged from their existing condition.

a. Erosion / Siltation

The proposed rip rap outlet protection will reduce the runoff velocity to a non-erosive value.

The proposed development does not intend to create or cause a change in existing conditions,which would promote any erosion or siltation on-site or off-site the subject property.

b. Concentration / Diversion

The proposed development will not significantly alter the existing drainage patterns. Theproposed development does not propose concentration of any existing drainage basin. Theproposed development does not propose diversion of any existing drainage basin area oralteration of the coarse of a stream or river.

4. Flood Plain

The County of San Diego has not studied this area; therefore County floodplain maps do notexist for this area.

FEMA flood plain maps do exist for this area; however, the FEMA map does not provideinformation pertaining to flood waters in close proximity to this project.

There exists a contributing drainage basin, greater than 25 acres and the location and width of thelOO-year lines of inundation are shown on the Tentative Map. See the attached Drainage Map 4and calculations for the width of the IDO-year storm lines of inundation at the point ofcomparison.

/./ .

LAMAR ST.I- ~l..L.. (J)0

0:::0:: -co~.2

CRESTDR)« «OJ -I

o>--JOJCDZ0::0-C/)

0::Wr-~r-ui

~C/)SITE~

VICINITY MAPNO SCALE

THOMAS BRO MAP NO. 1271, C-7

, I J •

. ! ; ., : r; in i./::I .... !! r ~. i l :

, ,

. I

. , .

County of San DiegoHydrology Manual

•Rainfall Isopluvials

I ........I."",u~"(inche.)

DPW-GIS....-..~--....... ---..

303Mlloa,....,

..;I

.t

I Rainfall Isopluvials

iJ11'1------------1

100 Year Rainfall Event - 24 Honn

_ -I 1__ ~_ISOI'l_u\/l_.._(_Incllo_S)_

III

31~ iI~II~1'I~:i__~_ I

I~po. I !.;: I I,

i: -1: I

i . ;: '

;I j , i ,, , II j I I , ,i

, r ; i I I i iI, , I : , ; II i ' I I , I , , I ,i : II i , i I ! I- I ! r I'31'~" ,

till ~ rr -II I I! ! I

,i

i II i; i '!::I , i l-I ! r I" i ' - I I I , I :; i ,

II

County of San DiegoHydrology Manual

•

-:

N __ ..""'lIo__ lQD_-.YfJI ......

~

==:.~..,:';::....,:::,:-~~c:.....- ............ _..._---_ ..- .......: B =-~"'_==_""'---.. ...--.....--------_ ...--.....5 '303MII ••,....,

,

EsE2

OcF

OkE

\ SmE

EXISTING CONDITIONS

-'p12A1~A6E. 13AsuJ LAw:.VL-A-r1 ON S

[!X'~T'NE':'_BASIN A: ~

_..A'RE.A = '-ll. ~ .Ac. C ~e.'DrA.': ("\o.~ tNla.f 1)-.. TIME.. OF CONCe.~TION = Tc:. = T; + 1+

"_":: 10.5 ~;r"\ (se.e. Tq,bl-e 3-2)T+" w.7 WIt't"\"" ( see h;vr.(. 3-t..()

Tc. = IO.5+~.1 = 17.2- ~.'..,

Tc.. = /7. 2 M..""

-.. I "-ITEJJS 1,,/ = I =.3.38tNjttR. (se.e hjvr~3-/)-.. RUNOFF C.Of..Fi=IC.IE/-lT = c..

"SOIL T'IPE. "B" = 2J. 'i Ac. \' 11. 3AC. peve(o?~ c= 0.38(~e TabLe 3-1; " 4.Uhe.. JJa..fvte>.. I .C; 6. 2.'S'

50'L T'1Pe "p": It7 AC\ 'Lf., A<:. Pev.e/ored c~a."/;,(~-e Ta.~e 3-1"') 5.1- A-c. Ntt-l-vrec.1 c:: (),36'

W E.\ ~ HT£D ." C:- \IA LU.E:. '.

-B: 0,3B(/7.3) + ().z~(4.{,);; tJ, 353 ?ZI.' ZI.'1

D' .o.<I(.(,4.5f-t-M;&.z). o. '13';1't.7 /'/,7'

0,55"3 (t.I. Cfl -r 0.43/ (19.7) :::0, 39LIJ~& _41, IJ "

C = 0,37Q= CIA - "_O~~t(~.~8)('-Ij,l~)=5"1, 8 c.-P~

0,00 = s« 8 ds ~k/~tl/Ei) _C~-

San Diego County Hydrology ManualDate: June 2003 Section:

Page:3

l2of26

Note that.the Initial Time of Concentration should be reflective of the general land-use at theupstream end of a drainage basin. A single lot with an area of two or less acres does not havea significant effect where the drainage basin area is 20 to 600 acres.

Table 3-2 provides limits of the length (Maximum Length (LM» of sheet flow to be used inhydrology studies. Initial Tj values based on average C values for the Land Use Element arealso included. These values can be used in planning and design applications as describedbelow. Exceptions may be approved by the "Regulating Agency" when submitted with adetailed study.

MAXIMUM.OVERLAi~D FLOW LENGTH (LM)& INITIAL TIME OF CONCENTRATION (Ti)

Element* I DUI .5% 1% I 2% I ~o/ 5% I 10%J,o

i Acre LM I r, I LM I r, I LM Ti LM ! r. LM Ti LM TiNatural I I 50 13.2 70112.5 85 10.9 100 I 10.3 100 8.7 100 6.9ILDR I I 50 12.2 70 ! 11.5 i 85 10.0 100 I 9.5 100 8.0 100 6.4,

i70rlO.5 D 85 100 i ,LDR I; 50: 11.3 9.2 8.8 100 ! 7.4 100 5.8' -

LDR I 2.9 I 70! 10.0 I 85 8.8 951 8.1 100 7.0 100 I 5.650 t 10.7wIDR i 4.3 50 \10.1 70 ! 9.6 I 80 8.1 95 ! 7.8 100 6.7 100 5.3MDR 7.3 50 I 9.21 651 8.4 80 7.41 951 7.0 100 6.0 100 4.8

110.9 50 ! 7.91 ,MDR 8.7 65 80 6.9 90 I 6.4 100 5.7 100 4.5

. IMDR 14.5 50 8.2 65 7.4 80 6.5 90 I 6.0 100 5.4 100 4.3HDR 24 50 I 6.7 65 6.1 75 5.1 90 I 4.9 95 4.3 100 3.5HDR 143 50 I 5.31 651 4.7 , 75 4.0 8- I 3.8 95 3.4 100 2.7).

N.Com I I 50 5.3 60 I 4.5 75 4.0 85 ! 3.8 .95 3.4 100 2.7G.Com 50 4.7 60 4.1 I 75 3.6 851 3.4 90 2.9 100 2.4O.P./Com 50 I 4.2 60 3.7 70 3.1 80 \ 2.9 90 2.6 100 2.2Limited 1. 50 I 4.2 60 3.7 70 3.1 80 ! 2.9 90 2.6 100 2.2General 1. 50 3.7 60 3.2 70 2.7 80 I 2.6 90 2.3 100 1.9"See Table 3-1 for more detailed description

BASII-J A3-12

.6.EFeet

EQUATION

Tc = Ch~iJt385Tc ::: Time of concentration (hours)L Waten:ou~e Distance (miles)

.6.E = Change in elevation alongeffective slope line (See Figure 3-5)(feet)

. 38~ TcHours Minute,.

5000

4000

JOoo

r.lfoOO~\ 5"2.80)2000 1+::;100

1000900000'JDO

,..60~"t-soo -,"400 " ,,~

,<9?;,~-$-,

""""" -,-,

-, 1

"

LMiles Feet

5

3

.6.E L Te

SOURCE: California Division or Highways (1941) and Kirplch (1940)

Nomograph for Determination ofTIme of Concentratton (Tel or Travel TIme (T1l for Natural Wafers!:,

fIGl:RF.

~

BASlIJ A

!l.uJIl.I-..+--l-i~I-~EQUATION

'1-. 1'-.1-, !IIII III I = 7.44 P6 0-0.645

5.0p....:.r..+I-...pj'd--+..:::.,f,J-'l~+!o..~:-Pt~~*F!'iolJtlt+lltflt+H+ltttttltHJl~ = intensity (in/hr)

1..j~-+t..~:hI-I~~I.+I"'~ltk:l+"""H=I"I.tJ~~f.I.fI:jilI=H.H+HtHII6 = 6-Hour Precipitation (in)/:::Q D40" t-. I • I D = Duration (min)

;j~3.0 I'. ,.", I ~I -I-I-1--f+.If+++t+J+I.J.Iillj4J.ljjj1-z> '" K I I III/III4m1U-l-l~1m~l"',,- I • ~ I-. I

100 i'.9.0 I-,8.0

'7.0 '

6.0 "

t..I· •

~ I0 ,~ I.t:g 1.0 :~09

i'2°8 I"£0.7

0.6 I0.5 I

I0,4

10.3 ..iz; --1= -- i= ._- I:::_-~.-

I

TJTTTT !

I

I ,

II

.3.02.5

_1 ... 1=. ._ _ _ _ __ _ _ - t'I111111111

0.2+-- e-I- - : - - .: - t:. . :IIIIIHIIII1I4:~.~IHr

-t-tI,1,II11 'II,

50 I

Directions for Appllcallon:(1) From preclpilallon maps determine S hr and 24 hr amounts

for Ihe selected frequency. These maps are included in IheCounty Hydrology Manual (10, 50, and 100 yr maps Indudedin Ihe Design and Procedure Manual).

(2) AdjustS hr precipitation (if necessary) so that it is withinlhe range of 45% 10 65% of the 24 hr precipilalion (nolapplicaple to Desert).

(3) Plol 6 hr precipilation on the right side of Ihe chart.(4) Draw a line through Ihe polnl parallel 10 the ptotled lines.(5) This IIna is Ihe Intensily-duratlon curve tor Ihe laealion

being analyzed.

Application Form:

(a) Selected frequency /00 year

(b) Ps = ~ In., P24 = ~ ,;6 = .!f..B...... %12)24

(c) Adj"sled pS(2) = ~in .

(d) Ix = rz.:z. min.(e) I = 3.'38 in.lhr.

Note: This chart replaces Ihe Inlensily-Ouration-Frequencycurves used since 1965.

San Diego County Hydrology ManualDale: June 2003

Section:Page:

360f26

B,4S/;J A3-6

...BAsItJ a.: (CFFS\TE. E:Xlsn~ ~ 'P£OPOSE.D)

AeEA :; 3. I.P A-c. (5.e.e Pra'/7a~ J1/I~f 1)'IME. OF COI-JCE.I-JTfZ.A:TIl>1-J ~ 7;,. ::: 7",'+ r;:

7;' = 7.'-/ M;y\ (se.e. TC4ble 3-2)Tt = 4./ MI'w'1 (S-e.L Fc'jlJrll g-~(')

Tc. ::.7.Y + L-j.7 ~ 12.1 1M:'"Te, : = / Z: ( V\A. t' >"'1.

I~TE.t-J'SIT'{ : I.:. 1./,2.'-/ •..../HRo. (~eeFI~ ur~ 3-1)J2.oNOFF C.OE.FF/C/EJ.JT = C

-S016 Type "B'\:. 2.3AC. D€.veloped C=O,38

sO I c... TVPE. "p..= I, 3 A<:. Oeve/ofeci C: ~,1~(5<~74h/-e- '3 - / ) --Y

WE.1EHITED C- VALue... =

0.38 (2.,3) -r 01"1,(1,3) : cJ, t./ I5,/; 3,'"

C = 0,4/Q = CIA = 0,~I (tI,zt../) (~.~) = &,2u cIs

San Diego County Hydrology ManualDate: June 2003 Section:

Page:3

l2of26

Note that the Initial Time of Concentration should be reflective of the general land-use at the .

upstream end of a drainage basin. A single lot with an area of two or less acres does not havea significant effect where the drainage basin area is 20 to 600 acres.

Table 3-2 provides limits of the length (Maximum Length (LM)) of sheet flow to be used in

hydrology studies. Initial T, values based on average C values for the Land Use Element are

also included. These values can be used in planning and design applications as described

below. Exceptions may be approved by the "Regulating Agency" when submitted with adetailed study .:

JMAXIlVIUM OVERLAJ.~D FLOW LENGTH (LM)

Table 3-2

& INITIAL TIME OF CONCENTRATION (T;)Element* I OUI .5% 1% I 2% 3% 5% 10%

LM I r, LM I r, I LM Ti LM ! T; LM T; LM TiI Acre

Natural iSO 13.2 70 I 12.S I 8S 10.9 100 10.3 100 8.7 100 6.9I

I12.1 70111.5! 85 100 ILOR I 1 SO 10.0 9.5 100 8.0 100 6.4

LOR,)

50! 11.3 70 110.5 I 8S 9.2 ioo l 8.8 100( 7.4- 100 5.81-

LOR 12.9 i70! 10.0 85 8.8 951 8.1 100 7.0 100 5.6SO i 10.7

MDR 14.3 SO 110.2 70 I 9.6 80 8.1 951 7.8 100 6.7 100 5.3MDR 7.3 SO 9.2 6s1 8.4 80 1.4 95 1.0 100 6.0 100 4.8,MDR 10.9 SO 8.1 65 1.9 80 6.9 90 I 6.4 100 S.7 100 4.5MDR 114.s SO . 8.2 65 7.4 80 6.5 90 6.0 100 5.4 100 4.3HDR 24 SO 6.1 65 6.1 75 5.1 90 4.9 95 4.3 100 3.5HDR 143 50 5.3 65 4.7 75 4.0 85 , 3.8 95 3.4 100 2.7N.Com I 50 5.3 60 4.5 15 4.0 85 3.8 95 3.4 100 2.1G.Com 50 4.7 60 4.1 75 3.6 85 3.4 90 2.9 100 2.4O.P.lCom 50 4.2 60 3.1 70 3.1 80 2.9 90 2.6' 100 2.2Limited 1. 50 4.2 60 3.1 10 3.1 80 2.9 90 2.6 100 2.2General I. 50 3.7 60 I 3.2 70 2.7 80 2.6 90 2.3 100 1.9"See Table 3-1 for more detailed description

3-12 BA?I1J B

�EFeet Tc

5000 TcL

4000 �E

EQUATION

= (1,!:,!!"'-~)O.385�E .

= Time of concentration (hou",)= Watercou~e Distance (miles)'" Change in elevation along

effective slope line (See Figure 3-SWeet)3000

O.3es-2000 -r; :1000

900BOO~O60~,t-500

',40ll "-,~

,~'».~

-,,-,,,

-,-,,

'1-,

'-/,7

LMiles Feet

"3000,-,,

-,,,"

L

SOURCE: California DMslon of HighwaY'! (1941) and Kirplcn (1940)

TcHours Minutes

5

J

Tc

FIGl:RF.Nomograph lor Determinallon 01 ~

TIme 01Concentrallon (Tcl or Travel TIme (Ttl for Natural Watersheds ~

5k5t/J 'B

Duration

2

.0

" ", :0 I II" ~.0

I'- " 1.0, I'- " ~ I It.0

.0 '........ I • I EQUATION

.;;f::::1:io..

I = 7.44 P6 0-0.645.0

.... I •I = Inlansity (In/hr),

, P6 = 6·Hour Precipilatio n (in).0" ...., 0 = Ourallon (min)

I' '" ~~ IlT!iIl1fI.0

I

1'0 .... , .... .........0 ........ " I'-

I

I'~"~

~ ...."]/1111: I I, ....

~ ....~: ....

.0 I.9 ,.8 lit7

...., ....~ 4,

6 :0 ILI,5 , ....

24 III ........

; .... 23 .- - - .. _. ._ ..- ~.- -- III.~-- - .. ...,. -- -- - - ..- .. ::=,-~:-

III -- -_. _ .. . - _. _. ,"... . - -- -- -- -- ;Ilfflll~. .- .. ~.... . - ...- - . .. .- --- - - .. ...

,I-- ..

- .. . l,....- - .. -- _. -- - - - -'

IIII~- ... I~::..=-: - ..

-- . - -- ••• - - •• 0 •

'1111111' .- _ ..-.

- . . ... I ...-- - ...- ........ ...'-

10987

6

5

4

3

o.

o.

0.

0.2

....>-- 0.1

5 3Hours

40 50 2 4 5 67 8 9 10 20 30Minu.les

6

Dlrecllons for Appllcallon:(1) From precipitation maps delennine 6 hr and 24 hr amounts

for tha selected frequency. These maps are included in theCOUnty Hydrology Manual (10, 50, and 100 yr maps IncludedIn Ihe Oesign and Procedure Manual).

(2) Adjust 6 hr precipitalion (if necessary) so Ihat it is within

lhe range of 45% 10 65% of the 24 hr precipitalion (no Iappllcaple 10 Desert) .

(3) Piol 6 hr precipitation on Ihe right side of the chart.

(4) Draw e line through the point parallel 10 the pi oiled lines.

(5) This line Is me ImansUy-duratlon curve for tne locauonbeing analyzed.

'fIs~=II3

6.0 "9 .5.5 ~.5.0 g4.55'

.0 ~3.5 ~

Application Form:

(a) Selected frequency J.P.Q.. year(b) P6 = ULln .• P24 = ....1e.-,~ = ~ ,/,(2)

24 .(c) Adjusled P6(21 = ZM.... in.(d) Ix = .aa.min .(e) I= ~ in./hr.

.0Nole: This chart replaces lhe lntenslly-Duratlon-Frequency

curves used since 1965 .

.5

.0

,P6 I: 1.5" 2 : 2.5 i 3 : ~.5! 4 . 4.5 5: 5.5 6Outalion' I I I I, I I i I I I J I

5 2.63: 3 95!5.27.6.59! 7.00:9221 10.54.11.66;13.17;14.49.15.817 2.12 ,3.18,4.24.6.30,6.36 .7-42/8.18 . 0.61 i 10.60,11.66.12.72

10 Ui8 .2.53;3.37: 1,21 ;5.05.5.00 8.74.7.58,8.12,9.27.10.1115 1,30.; 1.9512.59.3.24 J 3.89: 4.541 5.t9 , 5.84 i 6.19 . 7.13 . 7.7820 1.08: Ui2! 2.15; 2.89 i 3.23; 3.77,' 4.~1. 4;85 j 5.39! 593 . 6.4625 0.93. 1.10i1.87.2.33 i 2.90;3.27 3.73; 4.20 . 4.67 ! 5.13 5.6030 0.83 i1.24i 1.66. 2.07 :2.49.2.9013.32 . 3.73 : 1.15 i 1.58 . 4.9840 089 1.0301.38 1.72 2.07' 2.41 2.78 3.10.3.45; 379 4.13

• • • ,. • I ' .50 0.60 ,0.90; 1.19.1.49: 1.79.2.09,2.39.2.69 i 2.98: 3.28.3.58

. 60 0.53 ;0.80! 1.08; 1.33; 1.59;1.8812.12, 2.39 I 2.65 i 2.92 . 3.1890 0.41 ,°.611°.82; 1.02: 1.?3; 1.431 1.63; 1.84J 2.04 ~2.25: 2.45

120 0.31 ;0.511°.68,0.85: 1.021' 1.19, 1.36. 1.531 1.70: 1.87.2.04

150 0.28 ;044,°.591°.73:086,1.03' 1.18: 1.3211.47: 1.62.1.76

180 0.2610.39.0.52,0.650.78'0.9.1 1.04 11.18 1.31' 1.44 1.57240 0.22lo.33:0.43Io.54:0.85jO.78! 0.87: 0.9811.08: 1.10: 1.30300 0.10 !0.28;0.38/0.47 .0.56;0.88; 0.75: 0.65 0.9-1.1.03.1.13360 0.17 '0.25.0.33 042' 0.50' 0.58; 0.87 0.75 0.84 0.92 1.00

.5

o

Intensity-Duration Design cbart- Template 3-1

San Diego County Hydrology ManualDate: June 2003

Section:Page:

360f26

Table 3-1RUNOFF COEFFICIENTS FOR URBAN AREAS

Land Use Runoff Coefficient "C"

Soil TYpe

NRCS Elements Countv Elements %IMPER. A (B) C (D)Undisturbed Natural Terrain (Natural) Permanent Open Space o· 0.20 0.25 0.30 0.35

Low Density Residential (LDR) Residential, 1.0 DUIA or less 10 0.27 0.32 0.36 0.41

Low Density Residential (LDR) Residential, 2.0 DUIA or less 20 0.34 .CQW 0.42 cIDLow Density Residential (LDR) Residential, 2.9 DUIA or less 25 0.38 0.41 0.45 0.49

Medium Density Residential (MDR) Residential, 4.3 DUIA or less 30 0.41 0.45 0.48 0.52

Medium Density Residential (MDR) Residential, 7.3 DUIA or less 40 0.48 0.51 0.54 0.57

Medium Density Residential (MDR) Residential, 10.9 DU/A or less 45 0.52 0.54 0.57 0.60

Medium Density Residential (MDR) Residential, 14.5 DUIA or less 50 0.55 0.58 0.60 0.63

High Density Residential (HDR) Residential, 24.0 DUiA or less 65 0.66 0.67 0.69 0.71

IIigh Density Residential (BDR) Residential, 43.0 DUiA or less 80 0.76 0.77 0.78 0.79

Commercialllndustrial (N. Com) Neighborhood Commercial 80 0.76 0.77 0.78 0.79

Commercialllndustrial (G. Com) General Commercial 85 0.80 0.80 0.81 0.82

Commercialllndustrial (O.P. Com) Oftice Protessionat/Commcrcial 90 0.83 0.84 0.84 0.85

Commercialllndustrial (Limited l.) Limited Industrial 90 0.83 0.84 0.84 0.85

Commercial/Industrial (General I.) General Industrial' 95 0.87 0.87 0.87 0.87

.The values associated with 0% impervious may be used for dircet calculation of the runoff coefficient as described in Section 3.1.2 (representing the pervious runoffcoefficient, Cp, for the soil type), or for areas that will remain undisturbed in perpetuity. Justification must be given that the area will remain natural forever (e.g., the areais located in Cleveland National Forest).DUIA - dwelling units per acreNRCS = National Resources Conservation Service

3-6

Q,oo = ~,2lJ c.+sr1= a. 0 z:d= 1.5'... .~....

(a.,ScJ"'~ )s= o.oz: ,ttt'r1,'r!otUM

D= 7.J<.~ 0.30 -1- = t),5"Cf

D= 0,'1' < /,5' /.', Ca.((J.C.(·~ is C:;u-f+:c.i~+.

See.. Gl-4o..~e..d c~ ~ h oad WGl+er<k.~ •

....•

C,l.-l fl. f;)T.. ~ t·::,.. ~ \

~

Ieo-16e

156

144

EXM,i?LE(I)

Da36 in:I'IH (3.0 rut)O· &5 e t ,

(2)

(3)HW· H'It0- (h:l)

11) 1.8 ,..(2) 2.1 6.3.(3) 2.2 6.6

-0 in hOlt

200

:iUo'"<:ozs..

~...,D

HlIJ = 1,5'

'-I 'A1141' 14 bJe

~

1.5'< .L.f '

/.0

i

.6

1.0 .5

BuFfE.o1UOF pua~lc RO~O5 JArI. t9'53

HEADWATER DEPTH FORC. M. PIPE CULVERTSWITH INLET CONTROL

5-25 13(8 II

PROPOSED CONDITIONS

·

·.BASIN A:A2.EA = '-l1.l.Q A c, (S.e.e. DrC4I'~"~ VlIlQf 2 )

. TIME.. 01= c.O/'.keI-J/llA-"ON :: Tc:. .:: T; + T+

'Tt = 10,5MI'V"'. . ('5e.~ Ia.ble 3-2')T+: ~.-, -;'" (se.e F"ijv('~ 3-L1')

Tc.:' I 0 •5' + ~. 7 :: 11. 2- -.: .....Ie.:: 17.Z. ...-;""'"

IfJTE.N~rN = I:: 3.38'N/Hfl. (See. hjtJr.(. g-l)20NO~F c:.OE.FFIC.,e../'-JT: C.

Pfl.()Po~E.D C =~Z. 5Ac.. - SO/~ TYPe "0" PcveL.OP£D = O.L/" .5Ac.. - So;( -r.;!l. "e: f).ev~/oped : 0, '38 .....

I

WE./6E+TED C- VALUE..

0.38 (5) +O,Lj, (t.,S) = O."IDt, 77.5" 7.5'

0,L./{)(p (7,5"') +. 0,39 (5L/, ,) :. (/,·3f3'-1/, & 1/, te

C = tJ,393G: C:I:A;: 0,3<73 (3.38) (4I,/s,) = ~5. z.. c..fs. .. ... .._.__

Qrc 0 = 55. Z c -I's ( f't/1> fbscc') .;0;;0i:-.. ---

- - - - - - - .- - -DIOO = 51,8 cfsQIOO :: 55. Z. c.ls

£)«(:,-fr ""j >Ptopo'$-ec!.

0.L! (100)=.0,.7% -SLi, B ;",c;~~

.'. /iu-e.. ,''5 a o,L/cfs "ncyea~ //1 ro» oft a.+ +k.-'Po"(\.-+ o.f C6M Du-JtJH) t"'l. r:__.........'_...A\.·

..•.•............ ~....-.~..... _ ....~..- ..... _.,

.. _---~ - - .. _-- ---- - . - ----------------- -_. _ .._--_ ..- -- -- .. _.··.·.;...P\~TIN<fJ .SWAL.E.- @.4\u.. ~t",",'T o~ Co~PAtz.1$O~: pn •

....---..-.----.--(.'S~~.._J~~~$..~__...A ...CA~~.t.ATl~~5 __Ex~.:n~q-t~~p_) ....-.-.;

..--.~•...••.••...••~~~.••~:--.~-~Q~~ ·-;=·-~~·r_~--~;~--(i~,-~~~~-~J.~=.-.-_:•••-••.:.....•_..~-=..:_.~.•.=~.•=.:.:.~-.--...-._..-.:~...__..__J~.,~ ..:_6~~~cf?__(J;>g~J~P~~;C?~...__._.__... ...._.......... ~...-.-..--.-.-.L--n---8~~~._~.lR-T_'i. ==... _h_::_ 5._~__(_~pp~;~.Q.±~_._v~JY~--.---.---f

. .- ..--- ..... :.·..----.-&~ ij~ <AE.FEle IE~_=-._ ..V"\ :::: ..._ OrO:S 5'..___ .. ~

'Z.z..=

.. ...r:. . Channel CalculatorLe.xI~T'~C;;:l .Given Input Data:

Shape TrapezoidalFlowrate 54.8000 cfsSlope 0.0500 ftlftManning's n 0.0350Bottom width 5.0000 ftLeft slope 0.0588 ftjft (VIR)Right slope 0.2500 ftjft (VIH)

--- r:.. Cltannel Calculator~R.e.Pe~e~ .

. ----. Given Input Data:Shape TrapezoidalFlowrate 55.2000 cfsSlope 0.0500 ftjftM . n'annmg S n 0.0350Bottom width 5.0000 ftLeft slope 0.0588 ftjft (VIR)Right slope 0.2500 ftjft (VIR) _

Computed Results: Computed Results:.... Depth 0.7496 ft --. Depth - 0.7521 ft

---.-.. Velocity 5.6785 fps -- •• Velocity :' 5.6893 fps- Top width 20.7472 ft --.. Top width 20.7999 ft._--

" ,: ;.- --=~f~...~::~:!;,;1:·~/cok-lr~;;;.·-:~:I-~;:e.~:.;l..;..-et (~;.,=' '.._~a'1.d .?OJ/~~~cL(rr.kl(1~ ....~'1ei.__$.h(J(."...L_'& __cft..~a!..._~

- ...--Jr be~e{!1 ..~.. j :~._V/'c iYe1.l& _ J1ltlh '-~~.~_._...__.__ . .. .... _. '.. _ ...._- ....'.. - .... _--~-_._~

.......----~••.~:~:.n-__-~~~=_-._-_'_.~~~~•.~.~.( _.5_~__i~9:_i2t±~~_-~~~~~-W1;:p)~~__..-_. -- ...-. __~" ._TI ~ €..OF._~~~_<:.E.N~1t~_ :_._Tc. -~.T!~.._+:I+: . .._

.·-~~=::=-~-i~~_-~~'~:i:_:~~~~·~~~~=i~~~·=:, . _._.Te.;: 10 '.'5_ t__~.3 _:_J3,_BlM,l'(1 ......

Ie. ==. 1"3. BiM-l'""._'-•.--.--~.--~~---~,~~.~ \T.~_.~.I: =-·-_.lj_~O.~.~;~R--(~e .fl~U'r~g_l) -"-..-.'--..

. ._~ONOFf. CP~_F:FIt:IE.NT -:=c,t \0'

.. SpILT'{ PE:. P __ De-" E.L.OP6. C. .- - - -- _._-.~--~---._--~._-- .'-_._- ..- -.- .

--.------ .•. _- .••• _-_ •.• -.~._---- --.-- ••. _- •••.• _- ._ .•__ .• -- _.- ._---- - ----. --- .•... -- ._ ----.---------- •.•. - •.. '.• ' .• - ••.. . - __ 0,- _.,_" •. __. __••. _... .• '. __ •.. _. __ ._ ••..•. _._.

. D;: 5. '3 c..fs EO •----- -.- ...------- -------.--- ...-~- -- ._-(00 --.- -- ------ - ...----.---.-----.._. . _

==~===~~;;--~"_o",,~~~ve_,'5 -=&6.q,,-gff == -=.--..-.--.--~~.-----_rea.J;~----£lOJA.~------~-i--qV1~..----~.-£--~ . '. .--.-.-.-..--~--'P("~P-Q~.-----i2row d/i:et. -t..._$__ w,'/I r-ece ,'lIe •.-..----_~ k.e,4_L.,__._~ CA (~t.1j4._hj;/1 _~~wfi_. q bt:J1/.e.

---.,. ,.,-;.--'~$_CO(L'S_'_'W:_e~_~ uJpr~_l.~_5_~_evta.("~·o

,,'_. I ~rl c:1. • IS__~_Q(t (~-bt:.i>-~d;fch-('a.lc.c).'~tJb~L---.-..-.----~ --..-~:_---if.! b_ '!~_d&t_. _.___ .. ._._.. __~.__ . ~. .. . _

San Diego County Hydrology ManualDate: June 2003 Section:

Page:3

12of26

Note that the Initial Time of Concentration should be reflective of the general land-use at the

upstream end of a drainage basin. A single lot with an area of two or less acres does not havea significant effect where the drainage basin area is 20 to 600 acres.

Table 3-2 provides limits of the length (Maximum Length (LM)) of sheet flow to be used in

hydrology studies. Initial T; values based on average C values for the Land Use Element are

also included. These values can be used in planning and design applications as described

below. Exceptions may be approved by the "Regulating Agency" when submitted with adetailed study.

Table 3-2

MAXIMUM OVERLAND FLOW LENGTH (LM)& INITIAL TI.ME OF CON CENTRA TION (Ti)

Element* OUI .5% {1%) I 2% 3% 5% 10%Acre LM! r, LM1r. I LM Ti LM ! r, LM T LM T;. I

Natural 50 13.2 70112.5 I 85 10.9 100 110.3 100 8.7 100 6.9,100 ILOR I 50 12.2 70 ll..5 i 85 10.0 9.5 100 8.0 100 6.4

LOR 12 50 111.3 7( 10.51) 85 9.2 ioo ] 8.8 100 I 7.4 100 5.8LDR I 2.9 I

70 r-ro.o 85 8.8 951 8.1 100 7.0 100 5.650 i 10.7lYIDR 4.3 50 10.2 70 9.6 ·80 8.1 95 7.8 100 6.7 100 5.3MDR 7.3 50 9.2 65 8.4 80 7.4 95 7.0 100 6.0 100 4.8MDR 10.9 50 8.7 65 7.9 80 6.9 90 6.4 100 5.7 100 4.5MDR 14.5 50 8.2 65 7.4 80 6.5 90 6.0 100 5.4 100 4.3HDR 24 50 6.7 65 6.1 75 5.1 90 4.9 95 4.3 100 3.5HDR 43 50 5.3 65 4.7 75 4.0 851 3.8 95 3.4 100 2.7N.Com 50 5.3 60 4.5 75 4.0 85 3.8 95 3.4 100 2.7G.Com 50 4.7 60 4.1 75 3.6 851 3.4 90 2.9 100 2.4O.P.lCom 50 4.2 ·60 3.7 70 3.1 80 2.9 90 2.6 100 2.2Limited I. 50 4.2 60 n 70 3.1 80 2.9 90 2.6 100 2.2General r. 50 3.7 60 3.2 70 2.7 80 2.6 90 2.3 100 1.9"See Table}-l for more detailed description

3-l2 1

�EFeet Tc

5000 TcL

4000 �E

EQUATION

= C~}~t385= Time of concentration (hours)= WatBreoul'"5e Distance (miles)'" Change in elevation alongeffective slope line (See Figure 3-5)lfvet)

3000Tc

. Hours Minute,.2000

1000900000~O60} .,

t-'oo',4110 ',~

''''",. ~~,,

-,-,,

-,,,'1,

LMiles Feet

,3000-,

-,,,,,-,

L Tc

SOURCE: California OMston of Highways (1941) and Kirplch (1940)

5

Nomograph for Determination ofTIme of Concentration (Tel or Travel TIme (Tt) for Natural Watersheds

B~ltJ 1

FIGl:RF.r-:

10.0 II..... ~ r-.. , I Directions for Application:9.0

" ~ r-.. I-., i8.0

r-... .... '.... 1-., ...." (1) From precipitation maps determine 6 hr and 24 hr amounts7.0 ~ lor the selected Irequency. These maps are included in the

'" r-..,.. r--" ' 11111111 EQUATION Counly Hydrology Manual (10, 50, and 100 yr maps Induded6.0

I""I;~ I 7.44 P6 0.0.645 JII in ine Design and Procedure Manual).'r-o. =l>. (2) Adjust 6 hr precipitation (il necessary) so that it is within5.0 "' ....

I = Intensity (in/hr)

.... r-... ~ P6 = 6-Hour Precipitatio n (in) lIle range 0145% 1065% of the 24 hr precipitation (not4.0 0 = Duration (min) applicaple to Desert).

...." r-o.", ! ,(3) Plot 6 hr precipitation on the right side of the chart.

'''' "3.0 m I~(4) Draw a line through Ihe point parallel to the plotted lines.

, (5) This tina Is tho Intanslly-duration curve lor the location

"' .....I' " ....

being analyzed.I. ,

2.0

~r-o. " Appllcailon Form:"r-... 1

" 1-"" 'f (a) Selected frequency 100 yearI~ " .11I11li- "~i'

/11/11/g

(b) P6 = Z.sS In., P24 = ~ ,;6 = ~ %(2)i IIII- -,"

~! I ..,

3 24s: r-o., (c) Adjusted P6(21= Z.!'5' In. .l! 1.0 6.0 -g~0.9

I 5.5 ~.(d) Ix = .L1!.A.. min. ~,'*",

" 5.0 g·~0.8 .. r- 14

.5i (Il) I = ss: In./hr. : 7•.,q(I,B5"'(fi.~..

:50.7 ,"I"- 4.0 CD!

3.5 ~0.6Note: This chart replaces the Intensity-Duration-Frequency,

!-0.5~

3.0 curves used since 1965.

I0.4 2.5 ,.... 1"- m2.0

P6 I : 'i5 j 2 : 2.5 i 3 >51 4 4.5 5 j 5.5 6

:1111111 PUlalilln I I . I ' I I' I I I I I

"" 5 2.63 .39:,5.21.659 JOO. 922,1054.11.86: 13.11:14.49 15.810.3 1= - _.- - - -- 1 2.12 ;3.18,4.24.6.30; 6.36;1.42j 8.48: 9.64 ; 10.60:11.66.12.12.. - - .. - - F ::: I':: -,: - 10 1.68 .2.53·3.37;4.21,5.05.5.00 8.74.1.58,8.4219.21.10.11,

~- . 1.5 15 1,.30.: 1.9512.59,3.24: 3.89: 4.54' 5.19 . 5.84 ; 6.49; 1.13 . 1.18. - . '.. -

. .. - '. ... 20 1,.08, r.6212.15:2.69:3.23;3.71, 4-~1.. 4,8515.39! 5.93 6.48- ! . . :::.:.. :" ...... .. , 25 0.93 , Hoi 1.81. 2.33 i 2.60, 3.2113.13 : 4.20 . 4.61 ! 5.13. 5.600.2 3D:llfHJI: --

•. 100.83 i1.24;1.66; 2.01: 2.49: 2.9013.32 . 3.13 i 4.15 : 458 . 4.98

- - - -- . 40 0.69 :1.03: 1.38. 1.12;2.01.2.41 2.16.3.10; 3.45! 319. 4.13,. -. ,.. .. 50 0.60 ,0.90; 1.19.1.49: 1.19,2-0912.39: 2.69: 2.98; 3.28.3.56

- - --1-'- - _. - _ ... 60 0.53 ;°.6011.00,1.33: 1.59: 1.66: 2.12.2.3912.65,2.92.3.16-- - - - . - .- . r -- .. _. - - - .. ---" SO 0.41 ;0.6IjO.82, 102; 1.~3:1.•3i 1.63: 1.84 i 2.04: 2.25.2 .•5- - -- - -- : ...., .. ,- - _._-120-

.~- ",- .

~

1500.3. ;0.511o.sa: 0.S5: 1.02;1.\9, 1.36: 1.5311.10: \.81 . 2.04

- .. .,.' -. _. - - .. - - .. 0.29 :0.44,0.59Io.13:0.88!1.03' 1.18; 1.32 1.41.1.62.1.16ISO 0.2610.39.0.52, 0.65 0.78'0.9111.04 I 1.18 1.31: 1.44 1.57

0.1 240 0.22 10.33:0.4310.54: 0.85i0.76! 0.8i ; 0.08/1.08 ~ 1.19 :1.305 6 78 910 (0~ 20 30 40 50 I 2 3 4 300 0.19 ;0.28;°.381°.41.0.58,0.66; 0.75; 0.85 0.94.1.03.1.13

~I~.'!>Minu.les Hours 360 0.11 '0.25:0.33 0.42 0.5010.58; 0.61· 0.15 0.84 0.92 1.00

Duralion--.."... '" FIr. " D' F.

Intenslty-Ouratlon Delilgn Chart· Template 3-1BASIN J-. ,.' "'--

San Diego County Hydrology ManualDate: June 2003

Section:Page:

360f26

Table 3-1RUNOFF COEFFICIENTS FOR URBAN AREAS

Land Use Runoff Coefficient "C"

- Soil Type

NRCS Elements County Elements % IMPER. A (B) C (0 )Undisturbed Natural Terrain (Natural) Permanent Open Space 0' 0.20

.......... -0.25 0.30 0.35Low Density Residential (LOR) Residential, 1.0 DUIA or less 10 0.27 0.32 0.36 0.41Low Density Residential (LOR) Residential, 2.0 oUlA or less 20 0.34 @ 0.42 0Low Density Residential (LOR) Residential, 2.9 DUIA or less 25 0.38 OAI OA5 0.49

Medium Density Residential (MDR) Residential, 4.3 DUIA or less 30 OAI OA5 OA8 0.52

Medium Density Residential (MOR) Residential, 7.3 oUlA or less 40 0.48 0.51 0.54 0.57Medium Density Residential (MoR) Residential, 10.9 DUiA or less 45 0.52 0.54 0.57 0.60

Medium Density Residential (MDR) Residential, 14.5 DUiA or less 50 0.55 0.58 0.60 0.63

High Density Residential (HDR) Residential, 24.0 DU/A or less 65 0.66 0.67 0.69 0.71

High Density Residential (HDR) Residential, 43.0 DUIA or less 80 0.76 0.77 0.78 0.79

CommerciaUlndustrial (N. Com) Neighborhood Commercial 80 0.76 0.77 0.78 0.79CommerciaUlnduslrial (G. Com) General Commercial 85 0.80 0.80 0.81 0.82CommerciaUlnduslrial (O.P. Com) Ot'tice Professional/Conuncrcial 90 0.83 0.84 0.84 0.85CommerciaUlndustrial (Limited I.) Limited Industrial 90 0.83 0.84 0.84 0.85Commercial/Industrial (General I.) General Industrial 95 0.87 0.87 0.87 0.87

'The values associated with 0% impervious may be used for direct calculation of the runoff coefficient as described in Section 3.1.2 (representing the pervious runoffcoefficient, Cp, for the soil type), or for areas that will remain undisturbed in perpetuity. Justification must be given thar the area will remain natural forever (e.g., the areais located in Cleveland National Forest).DUIA ~ dwelling units per acreNRCS = National Resources Conservation Service 1.

3-6

0'00 = 3.3 c+s .r'\ = 0.02..,

d = 2'5 = Zl. (M"~)

I at-=-- If.. ($. '3::1- (z.) ~(o.O'L) - __ "r" 1<... = (J, ~73r;;-

.~ O=~(d)/3(S)/~('\

_ .._* Pe., 8t't7..fe;.,- e; L(;..~.

-, ~.;. ... "

...BAStl4 2 : [ PRDPD,;EC]

A~C:A: II.lt AC (~ 84'5/l-J 2.. D~II'.JA6Eyn.¥)TI~E.. OF- C-ONCEN.Tl2ATtCN = Tc.::= ',·+T ....

Ti:: IO,5M(~ (5e~1Qb/e s.z::1; = 7,1-"" (';--,(Se~ hjcM.t 3-J./)

k.:: /0,'7 r 7. z. :::/7, 7 "..,~Tc. :: /7. 7 ~,~ .

JNTEJ.Jsrr{ = ,r ='3,32. 'N/fiR.. (~hjr,H'{ -g-J)R.Ol-!oFF c..ocFFfC.t orr: s: L.

SOlLT'IP€" "8" = '-I,IAc. [)evelo?ed C"'"tJ,58SOIL .. T'fPE. "D" = 7·5 A.c. z;Jer/~JojJ<.d C:;o.L/'

l()et6HT£D C- VALUE-" (See. --,aWe. ~-/)0.38 (4,1) of- (),l/t, (7.5) = (J,J./3

II. LR . /1. [,

C = CJ."3(Pra?~d)Q~ LIfI :;:(),13 (~.32-){tI,/..p) = //P,_~C:.P5

~oo':: /IP,(p c.fs -C~_--

~ ~()O - ;jhAWT7 c;bcv.e /5 ~ Itt.;~ff-. f'~k.. -flow', ~I tlJ1~ .~. ~ /rP/O,u

...... StorNl d,rar'r1pri7€ S w;/I r.ece/v'.e. ,... -t/tw.t.(Jy.e I ~ cabla-lr~ ~~/l q b::ve

,'5 c.Q,'1'7r'c!..ev-~d .~ WtJ('51- co se: 'Sc..eVlaf'i ~

." arid /5 ~ "Y1I':J S!o,M ~(i-1 $:1$i-c~Co ~ leo {a.,-It.~II/ D/2J t/t 'cUd.