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<br />costs of conducting the studies that resulted il}the overlays of flood-ha~dareas. (See Appendix />
<br />II, "Map Production and Maintenance, "f9r;ddiscussion oj studies);';/ , />/
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<br />The accuracy of the flood mllwfs a major concern to.-ttJet:ouncil. Existing mapping':>'-
<br />technology allows for infinite acpy~c~ given infinite fUIJdf>fn the real world, howeve~,.-aJhnaps
<br />have inhe~eW limitations, ~~;n:itionw~~,~F1P. m~ppillg prog~am is limited by th~~~e4,\~
<br />operate wltJ:im fiscal constr;unts. AccuraC)('~~y a functIon of the age ID)iljOsltlOnai>
<br />accuracy or base ma~,~n(j the accuracy ofl1yctrologic and hydraulic data u~~.(o determine">. /;:~
<br />flood elev,ations, ~accuracy of these components is related to the fun~ds:.aVailable to compile>" /,-,
<br />the infofmati@<Greater funds allow for more precise study and mappi'pg methodologies, '</>/
<br />resultin] iwi'eater accuracy. Each of the components contributing1G/the accuracy of the NFIP />
<br />LIMIT or, I . ,/./ .. . . /' ,/ ////'
<br />DETAILED stl Ilyrhaps IS discussed m detail below. //' ///
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<br />'Age. Many base maps are old-some older thaIY~5years. Features that exisJ~en a
<br />FIRM is produced-new subdivisions, road~,.jirt'd highways-may not havlexisted when
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<br />/'tj-re.il3~'e map was created. When older bflSi:1l1aps are used, the newer ~9a.dS and streets
<br />'zOiffalle ~ssen!ial reference points do nOt-appear on the FIRM. Determirtlng whether a /
<br />'particular parceiorbuijding is wit*br outside a floodplain depe6dS' on being able to //
<br />"' locate the structure accuiate)y in ~e)~tion to other known phy.stca1 features. When roads /,:':/
<br />.-foNE Aj!I1d streets are absent from tile F,IRM, or have been chan.llejl(the potential for errors in the / ;,'<,
<br />determination is increased. When.'F-ElyIA begins to up<Ja(e a map, it sends the impacted /> " '
<br />community a letter informing it,bftiie~lI1ld re,({6esting it to submit informatio~("'..
<br />would improve the accuracy dJ/utility of its lrrap~J(Nhen the community submits,.!1fap-s '<
<br />showing updated road networks, FEMA incorporllt.~ the information to the ex~i that it
<br />is in and _around flooding./Ae comI?unity. is .given 'a,:s~cond opportunitr~9"-siibmit
<br />mformatlOn when the map rs Issued m prehmmary fo~,. //
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<br />! !HorizontaI and Vertical AcZ~racy of Base ~aps. As an h:~1e;Cthe scale of USGS
<br />! / quadrangle maps, often used,~ase maps, IS 1 :24,00? (e}.~)'inc~ equals 2,?00 feet) or
<br />I' smaller. zMm k:JSGS quadrangles-life also mapped wltfr'i}'Contour mterval (hnes of equal
<br />/~/ elevation) of 5, 10, 20, or 40 feet. 'TI:1'e.,selected int~J'jar1s primarily dependent on the
<br />// topograph)S'ietie(ofthe areas being rna:{1ped.~~tlonal Map Accuracy Standards specify
<br />// that not IlIpfe thiih'1:.?~ercent of the elev'a~g~.tested shall be in error more than one-half
<br />_ .-;/ the co~iotu interval.. l'hlz~ans that ~9t-/f)lore than 1 0 pe~cent of well-defined points
<br />testecV?h the map wIll be lil~trQr by Jl'l.ore than 40 feet honzontally. Due to the
<br />limi~ions of accuracy of the b8;G$'quadrangle maps, as well as other base maps having
<br />simiial-.':sqIles and contour in~s, buildings near the edge of floodplains can b~,_,/~..:~:,~-:;:;.. ..
<br />subjectedie"::\>ot!'1 floodpl<jU(management regulations and the mandlltg.ryAJ:(JJj4~ie:P
<br />purchase require~nt #iI, in fact, they may be well outsicjetheJlfl'odjijaffi,"/
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<br />These li~kations are compounded il},are~~reiio detailed studies have been
<br />p~rformed to {'1ermin: the BF~. The.F:~(}:,!:ffazard Boundary Maps (FHBMs), crea:e?
<br />WIthout benefit9fg~ta!~.tlstl1dl~s;:ti?-v>,been converted to FIRMs for many commumtIes.
<br />: These F1RM,Sare'iH:lQ,pled;byW-Utiits of govemment for floodplain management, and
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<br />_~:::___~e_bein~~,d .by 1~~et%;::j9sU1ance agents, and n:ap determina:ion firms to mee:
<br />-"---msw:ancei-eqwr<ll!eiifyW.hereJlfJl.5,are not avaIlable, comparison of the elevatIOn of a
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