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<br />IV. ALTER....ATf.I)RAIJ'oiAGE li\-IPROVDIE~T f:V....LlJATlO!\
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<br />,,,",. General
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<br />Th~ hydrologic analysis performed for this report indicates development will increase the magnitude of
<br />flood peaks Drainage improvements are required to safely convey t100d peaks produced under fully-
<br />dcvc!opcd conditiollsto mlllimiJ:epublic health and safety concern s and property damage from flooding,
<br />A number of drainage improvemem strategies have been reviewed by the Advjsory Board dunng this
<br />phnseofthe\Vork. Oncstrategy, the null or do nothingalternme. was rejected bccause 0 fthe desire to
<br />protect the population as well a.s legal issues_ A conveyance strategy, which requires channel capacity to
<br />convey lOO-year flood peaks produced under fully-developed land use to major streams, \Vas also
<br />rejected because of potential damage to downstream property owners, costs. and legal issues A third
<br />strategy, which uses detention storage to reducetlood peaks from developed areas coupled with the
<br />construction ofadjoiningSlOrmwaterconveyancc facilities, was sele cted for further investigation,
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<br />The potential components which could be used in the storage/conveyance strategy were investigated
<br />The Advisory Board reviewed the advantages and disadvanlages of a variety of stormwater storage and
<br />conveyance options, which are summarized below in Table 11.
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<br />Table 11. Advantages and ()jsadvlIntllges orSlOrmwaterControl Elements
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<br />DETl:NTION FAClLlTU:S
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<br />R"j/:i<<n~J D.'1enliun
<br />. Ad'~nl~Ke.'
<br />. prodi~lablc rcdu(.1ionoft100dpcak5
<br />. rakcad\'am:lgeofhydrographuming
<br />. conwuctinnmustoccurCOr\Curr<:Jlt!ywithupoucam
<br />developmenl
<br />. communityplaurungJX>lCnual
<br />. high muhi.u.<<: polcnlial
<br />. cOInbincwilh'c",e"l,o,",lf...,l,I,C'
<br />. eas\errounneinspc-ction
<br />. lcwmaimen:",ce
<br />. moder.!tcbndrequiremems
<br />. majntainhistori~e:n~hmenlarcasandflow p'\lhs
<br />. n1;\ybe~ombinedwithwalcrqu:,lilyBMP"
<br />. oo'llll.!rinu "sib.lilic,
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<br />'"'
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<br />,
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<br />J)i,f<Ulwmtlllie,,'
<br />re<jum:.modcr-.!tctopogrophiclelidloachicvc
<br />"olum<
<br />high initial COSI
<br />IUlrdtomodif\'ifimr<r,iousncssin.;re,,,",up"ueam
<br />ofpond
<br />highlj' mual ifpooTl~ de,igned
<br />n:qulfe, strong institutional ,rom.'wmk
<br />implcmcllI;u,on
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<br />Table II. Ad\'unlages and Disadvantages orSlormwatu COlltrol Elements (colll'd)
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<br />D[TENTlONFAClUt'l[S(rontinocd)
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<br />~imaleh2to30",,=)
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<br />.
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<br />:"ri~bb<..bllod Detcntion (calCltmern orOJa
<br />AJvantll/!"_'.
<br />dc,lea," =lofconv"l'ollee,yllcmoo..'nSlleam of .
<br />NO"
<br />n;<1uI;C flooding potent,al of con,"cj'once ,Yllcm
<br />downslrcamofpond
<br />c",olcpockcuofopen,pace,ndevelopm<:m,
<br />incorpor.lted in small neighborhood park.,
<br />i1e~ibleJllaccmentand,ize
<br />OJ'~' torequire developer funding
<br />homeowne"organva\ionmayrnainlain
<br />oodlocalionfolwatcr ua]ilV'im o"cmenlS
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<br />l.<JcaJDctcnlion
<br />AJvantlll:e..
<br />incorpoMeinsilepJan .
<br />canbcfundcdandbuiltby,itcdc".cloper .
<br />mJima;ncdby l:mdo"ner .
<br />fle~iblc~ignmodifica!ion" .
<br />n,-cragelocal;on[orwa!crquatil,.improvcmem,
<br />docs nOl depend on regional facilit,es bcingin place at .
<br />lim<ofoc\'cJopmcnt .
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<br />Di.,~Jvon/<JI:.'
<br />non_l""d.JC1ablchv<1rologicrcspoMC
<br />,mall oullct work,ca<llyblockcd
<br />minimtunfa;;torofS;lfelY.jfdc,ignovente~cce<.icJ
<br />poorlj,.prcdietable de,iV' c\'cnt inerea..., unecnai"l~
<br />m"",C
<br />eanmooifyhi'lonceatchmenlar<asandflowp:Jlhs
<br />bom""wnc" olganumion ma~. not main!;]in them
<br />flcqucnlin,pcction'
<br />higl1e' unit mainlcnance co,ts
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<br />Disad'nnmg<l..
<br />non_prcdi~1:lbtehj'drologic le'ponse
<br />smalloutlelwo,,,,e;,,ilyblockcd
<br />miTlimumfactorof'afcl,.;fd<,ignc'entc~ccc<1cd
<br />poo,ly_prcdictablede,ignc"..cmincrca<e,uneCrlainlV'
<br />In Size
<br />[lcquenlin,pection,
<br />lnainwincdb~landownel
<br />lughelunltmainlcnane<:C("" ,"~uj""m"",luJl<l ""l
<br />,,,oc for brge II\H"Ocr of dc'1ention coli... in "
<br />c",ohmcnl
<br />m:untCD,nccnototlcnp<:rt"ormed
<br />unrcpur1c<lnlOOi!~~_I~O_,!,
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<br />CO:"VEYA:"CE
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<br />Ibrd jConoretrJRipr.p Lined) Channel,
<br />Ad"'~nl"ge,'
<br />sm"lI~fC~ fo,cooveyonce
<br />det1ncdbound:uic,
<br />,wrmwaterqui"kll.tr,m'ponedthluug!lthea,ca
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<br />DiSddmm"ges
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<br />. high,et<)<;;l,."
<br />. n'ghpolentiatp"hhchcallh;'",Jfctvhal...ro
<br />. poor,'islL~1 impiot
<br />. h,r)t inili:d cost
<br />. highmaintcnancc
<br />. can inele~sc flood peok n~Lgnil"<ks
<br />. m~gnclfOI"andalism
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<br />IV-l
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