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<br />III. HYl>ROLOGIC .\(01)[1.
<br />
<br />A. General
<br />
<br />,
<br />I
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<br />Flood peaks and hydrographs for each oflhe three major sub-watersheds in the study area arc
<br />defined using liDS\V\195 (UD$ViM), calibrated to CUHPF for the lOO-year ,torm event Standard
<br />routines in ACAD-14 and Soft Desk computer programs were used to identify baSin parameters
<br />required for CDSWM and CUHPF, The detention areas are modeled using HY-8 computer
<br />program. Irrigation facilities are assumed to not transport stormwatcr. Catchments, flow paths,
<br />design poims, and catchrnent and conveyance element identifiers are pr esclllcdon Figl.lres2a.2b, 2c
<br />and 3 in Chapter II of this report. UDSWM: flow charts for tht: hydrologic model arc presented in
<br />Appendix A of this report,
<br />
<br />B.
<br />
<br />UDSW:\'lllOd Cl"HPF Parameter!
<br />
<br />Precipitation depth and distribution, were obtained from BouMa C"'mly Slorm Druill<J[:e Criteria
<br />Maml(l{(DoulderCountv.1984)andarereproducedinTable2.
<br />
<br />Table 2. PreeipiUlion Distribution for UDSWM
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<br />,
<br />
<br />Time 100)r. 50)r. IO)'r. 5)f. 2)r. IIA"/hr
<br />(min) (inlhr) (in/h.) (in/ill) (lwhrl (;n;br) (in/h.)
<br />, , 0,.16 0,36 (J.:16 0..16 0.2~ "
<br />W 0,96 0.% (J.n (J,(;!) ()...S 0,1:
<br />l, '" I (,~ , nl..
<br /> I..... '" , n%
<br />20 2.6.. i :,2R 3,12 2,52 I 1.92 11,36
<br />25 ",56 ",32 '" ..-'2 I '00 O.~,
<br /> ,.
<br />311 R,l(, 7,211 25: 2.1).1 1.6S UO
<br />., -1.56 HR 1.20 (J,9(, , o,n 1172
<br />~.
<br />'" V;-I 2,2R O.R.. (In n6n n.lf.
<br />" 2,O~ l.~.. (JR4 0.(,0 ()36 0.2..
<br />50 1.6~ 1.4.. 0.72 0(,0 ()36 V.2..
<br />5, 1..'2 O<il' <'\.72 o.~() 'U6 fI.2"
<br />'"' 13: 0.% I 0.72 (J,6() \1.36 11.2..
<br />"' 132 11.96 072 0,60 'U6 fl.:..
<br />'" 0.60 0.72 I 0.72 O[>{) ,1.2.. 0.1:
<br />" ow 0,12 , n.n 0.60 fl24 V.12
<br />"" \1.3" "" OAR O..R 'U4 ,
<br />"' 0,36 o..s {U6 0.36 0.2-1 "
<br />'>0 ,n~ 1116 ();(, 0,1(, O,2.j "
<br />" 11,.16 0,.1(, 0,3(, 0..16 \12.. "
<br />Ii," 0..1(, 0,3(, 0.36 0.36 , 0.24 "
<br />)1)5 \1.36 (),.'6 {U6 11.>6 I 1)24 "
<br />"" 11,:;0 IUI, U.3~ 0.:;6 n.2-l ,
<br />11:1 l!..il, O.3h 11..11, 0.:.. I 1),12 ,
<br />12\, "..'0 O.J6 [J.N iU.. nl2 ,
<br />
<br />From BOl\ldcrCwnl\. 19S.., "T"ollol\lD<si;;nSIOtmforB"\1nsL~ssTha" Fj"cSq,,",~'vjilo'"
<br />:--;"'" 1.I"pp' J.:p,hs :';'~ Un" J-,r- 1.-1,", 111-)r U~", .'"-1.;' :..". :!X\"." ,7"
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<br />Catchment parameters, including area, ~trcam and basin length, slopes, and di5tance to centroid were
<br />identified ming recent (1999) topographic mapping (Aztec Consultants, Inc, 1999), Area and length
<br />mea,uremerns '-"ere obtained u,ing the Inquiry Module of ACAD-14 and Soft De,k computer program:;
<br />Parameters for indiv,dual catchments for lJDSW:..1 are listed in the computcr oUtpUl summary in Appcndix
<br />A
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<br />Hydrologic soil group, and land use '-"ere overlaid on the topographic mapping, areas obtaincd using
<br />ACAD-14, and catchment averages were determined u~ing area-avera.!je calculations \Veighted soil
<br />parllmetersrcquircdforthcmodelincludeinitialllndfinlllinfiltration (in/hr) and decay coefficient shown on
<br />Table 3 SOlI parameter, for individllal catchments are li>ted in the computer output summary in Appcndix
<br />A
<br />
<br />TableJ. Soil Parameters
<br />
<br />NRCSllydrologic
<br />Soil Grou
<br />B
<br />CandO
<br />
<br />inlhr
<br />
<br />D~cayCl}l'ffici~nt
<br />
<br />Infiltration
<br />Initial
<br />4,5
<br />)0
<br />
<br />Final
<br />0.6
<br />0.'
<br />
<br />O.OOIS
<br />O.OOIS
<br />
<br />The :ype and density of land use defines the magnitude of the percent impervious parameter used in the
<br />hydrologic model pcrceru impervious for various land uses are lisled in Table 4. Percent imper.,.iousnes~
<br />for individual catchments for existing and future conditions are listed in the computer outpUl summary in
<br />Appendix A
<br />
<br />TlIbl~ 4. PH(~"t I"'l'~f>jous Fur Lan<l Uses ill Sto<ly Ar~;l
<br />
<br />Land Use
<br />Op.nSp.ce/Agncultural
<br />GolfCourse/Park
<br />Railroad
<br />Low D~~lSlty Resident,al
<br />.\lediumO.nsityResidential
<br />High D~nsity Residential
<br />Schools
<br />Industrial
<br />Commercial
<br />
<br />%.!~pcrviou,
<br />I
<br />7
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<br />"
<br />JO
<br />"
<br />"
<br />5D
<br />00
<br />05
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<br />t'DSW\1 ralehm~nt width (W) parameters were calculated uSing,
<br />
<br />w ~ L" {:- [{:\J-A,).'A,j: (Huber eta:, 19S~).
<br />
<br />wherc L,. = lenf'th of th~ channel. A; ~ area on i"' sick of the channel. and A, ih~ ioial area oi' the
<br />~alchm~nl .-\11 ~lm\~\'ance clement); were simulat~d with a main clement ill\d :lll overbank clemenl
<br />Follo\\'in!" rL'Commendalinlll in :Iw l"DS\\:r.l manual (B"vle F.nginl'Cring Corp. It)~5) f(llJ!!-hn~,j
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<br />1II.1
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