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<br /> TU;!; Rilin:.all IntE'flsity ,
<br /> ,
<br /> (ll,ir..) ,~ If' ' ,
<br /> '..n. .LI
<br /> 2 'Jr. 5 Yr. I 10 'ir. 25 Yr. 50 ". 100 Yr.
<br /> 5 .01 "" "'" " 48 " 60 .60
<br /> 10 .36 " 48 "60 ." .84 .36
<br /> 15 "'8 i .60 . " .9G 1.08 1.44
<br /> " .1i0 .8.1 .% 1.32 1.68 I 1.68
<br /> 25 .8' 1.56 2.16 2.28 2.40 3.00
<br /> ,
<br /> 3C 1.80 2.52 3.12 3.72 4.44 i 5.04
<br /> ,
<br /> 35 3.24 4.68 "
<br /> " 5.64 6.84 7.92 9.00
<br /> 40 ,
<br /> 1.08 2.04 :,.28 2.Sf! 3.24 3.72
<br /> 45 "SO 1.08 1.20 1.56 2.04 2.16
<br /> 50 " 48 "" .84 1.08 1.44 1.56
<br /> 55 . 3 6 " 60 " " .84 . 96 1.20
<br /> 60 .36 .48 .60 .72 .72 .08 i
<br /> 65 .36 ". ! .60 .72 .72 .G\J ,
<br />I .'j,.)
<br />I 70 I ." .36 "48 .4R " '" .40
<br /> I " ,
<br /> 75 I . ~1 .36 .36 .36 , .36 I .36
<br /> , I ,
<br /> 20 , .24 i I " I
<br /> , '" .').4 .,f; , '" . 'if;
<br /> "' ." .24 .24 "36 "24 ."
<br /> 36 ." .24 "12 "36 .24 .24
<br /> ,
<br /> 95 ." .12 , .12 .24 .24 .2!,
<br /> I "H I
<br /> 100 .12 .12 .12 .12 2' ."
<br /> , " .
<br /> "
<br /> 105 I .12 .12 , .12 ." ." .24
<br /> UO I .12 , "12 I .12 "12 "12 I .2/,
<br /> I
<br />
<br />, U,
<br />L120
<br />TOTAL
<br />PRECTP.
<br />(tn.)
<br />
<br />."
<br />.12
<br />1.10
<br />
<br />';'"B:~l:. ~
<br />WSST V~NE D~AT~AGE nASl~
<br />
<br />IE:;IGN P]d~l'"l\LL
<br />~-
<br />
<br />.12
<br />
<br />" " .12 "12
<br />.12 .12 .12
<br />1.84 2.25 2.',7
<br />
<br />.12
<br />
<br />.12
<br />
<br />2.89
<br />
<br />P",rCf'nt
<br />of
<br />Total
<br />
<br />1.7
<br />U
<br />U
<br />4.8
<br />8.7
<br />14.5
<br />26.0
<br />10.7
<br />6.2
<br />U
<br />L5
<br />2"'
<br />
<br />1.7
<br />
<br />1.2
<br />LQ
<br />1.0
<br />0"7
<br />0.7
<br />0.7
<br />0.7
<br />
<br />0.7
<br />
<br />0"7
<br />IJ.J
<br />0"3
<br />
<br />C?.{.)
<br />
<br />. 1 2
<br />
<br />1.55
<br />
<br />nr.1:
<br />
<br />I UBL.~
<br />
<br />DESIGN RAINFAll
<br />
<br />_1 ~_
<br />
<br />i
<br />"
<br />,
<br />I
<br />I
<br />
<br />hi1sed model. Accuracy is del-'endent on repr~scntinq th" act:u.1l
<br />physic<:<l characteristics in the field. Therefore, significant
<br />changes in overland flow slopes, ext~nt or type of develop-
<br />ment, and overland flow lengths were represented by modelling
<br />smaller subbasins. The subbasins we!'e deline"ted using the 100
<br />scale, 2 ft. contour interval mapping provided by the City.
<br />Field investigations were carried out as necessary to define
<br />those subbasin boundaries difficult to determine from mapping.
<br />Subbasin sizes ranged from 1.8 acres to 156.8 acres with the
<br />median size being 14.3 acres <:<nd the average size being 25.5
<br />..cres.
<br />
<br />IV.D. Influence of Physical Features on Hydrology
<br />
<br />As stated previously in this report, several existing detention
<br />and retention areas exist throughout the drainage basin, sone
<br />of which are natural whilf' others are caused by road embank-
<br />ments, railroad embankments, or development. ~any of these
<br />are<:<s exist west of Dverland Trail on property owned by C.$.U.
<br />All existing detention <:<nd depression areas were modelled [or
<br />the existing dev"lopment condition. The City has little
<br />control over future dcvelopreent on C.S.U. property. Therefore,
<br />for thi> hydr"'lo<ji" "'1"ly<<j" of f1lt\1r<' d,"v""l(]p"""nr, rhro\1qh
<br />mutual agreement with the Technical Committee, existing dctllntion
<br />and retention areas east of Overl<:<nd Trail were modell(>d <:<$
<br />they ~xist. Detention areas west of Overland Trail were
<br />eliminated with the exception of College Lake. College Lak",
<br />was modelled <:<s a detention facility <:<ssuming the lake was full
<br />to th~ crest of the e~rgency spillw<:<y at the beginnir.g of the
<br />des~gn storm. D~scharge ch<:<racter~stics tor the spillwdY as
<br />prcs~nted in the "College Lake Improvements Study" 11) Wrl1re used.
<br />
<br />The four irrigation canals which traverse the drainage basin
<br /><:<1'''' Capable of int.ereepting a siLjr.ificant portion of minor
<br />stOITI runoff bas,~d on current. le-V'"l$ of (leveloprr-cnt 'Nith the
<br />assumption ~hat the c~nals are not running full with irrigation
<br />'~'ater. However, for purposes of this hydrologic analysis,
<br />
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