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<br />/;/ The Coun\~l~~ reviewi~ entire subject ofrriap~ac<:Ura€f~oaIilHCtllgflie-relatforship
<br />:;/ between costs requir~ to proiluce floodplain maps and the levels Q~ accuracy needed b~ rhe
<br />\ diverse map user coni;UlU~s. Although the group will engage iri q;onsiderable discuss!~n <
<br />i<::". before it makes~~.9.~~ations regarding this issue, its import~fe diclates a discussi6nji1~/
<br />\, ""\._ report. /---;'>---- '\:- \. " i
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<br />',\, /-;:;/When FIRMs are crea~d, the information depicted is tYBi~ally derived from three
<br />'\'v;jimapping sources: the work map"~4e base map, and the cqJIll!!iinity map. The work map is a
<br />..</ product of a study contractor, anftJ1lc'cJudes strip maps of floodplain areas used to delineate the
<br />I /;/ floodplain boundaries. FnUyls)'asea.~ a detailed study are generally more reliable than those
<br />I /;/ based on an approximatt;.4UdY. The b~e,map is a map that covers the entire geographical area
<br />~/ of the community an9--~icts physical fe'aiut-es, most notably roads, needed to determine the
<br />location of speciticPfo)l~rties relative to th&Jl~odplain. The topographic information contained
<br />on the base ~i(tYPic~ll~not as detailed as\~'l:,topographic information on the work map,
<br />which is us~to actually de1i~eate the floodplai~b(Jundaries. The community map is usually
<br />used only\~ a reference sourc~for road names anCt{or information on current corporate limits.
<br />\ '\ \ \ \. .
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<br />The pl\.blished FIRM is a c~h):pilation of pertin~tjnformation from these three mapping
<br />sources. The hY\h:.ographic data, flooiiPlain and floodM(a~boundaries, BFEs (one-percent annual
<br />\.. " \. \ // / '- \
<br />chance), and crosg".~ction locations are'tl1ken from)he work,\map. The corporate limits and road
<br />names and location~'ln:e taken from the ~s~ ,~( Finally, s~lementary corporate limit and
<br />road information is tak~:nJrom the c()~ map. Because ofpqst constraints and the intent
<br />that the maps locate flootL~dSiehu(ye to specific properties, ~hFally the roads in and near
<br />flooding and major roads outside of flooding are included on the FI~:
<br />-'" \
<br />
<br />The primary purpose of the NFIP mapping program is to identitY '~whazarg51lit]ie;:;=;~;- / "'
<br />than create base maps for the communities that participate il1,~aiR;::e{jIii;~(f~ntfy;/ ,,'"
<br />existing base maps available from otherf~deral,stare;Qr.kroatjoitices'1rreus~ as base maps for
<br />I FIRMs, This i,~~llt~J1(\e4~~~~vhl~~~tnafthelim.ited flood stiJ~.funds can be
<br />I (n)_"SI'~~n-:"~ll~Ill!lIfpmgthe fToodplam areas. The 7.S-mmute topographl~q,uadrangle
<br />t~:::::;c;;c:cC:'1I'IllJlJ>'::pfoifueed"bYfue U.S. Geological Survey (the federal agency charged with dev.;~ping and
<br />-'" ""maintaining large-scale topographic maps of the entire country) are the most accurate'~ps
<br />available for a community. They are used frequently as base maps in the production offIRMs.
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<br />The Council found that the pragmatic decision to use existing maps as base maps fOI\'\
<br />FIRMs is the cause of many of the frustrations expressed by users. The decision, however,'>
<br />seemed reasonable at the time it was made, and it still makes economic sense. Inconsistencies in',
<br />the accuracy of the base maps and between the base maps and the work maps nevertheless lead to'\O' ,
<br />inconsistencies and difficulties in interpreting FIRMs. The NFIP was not and is not geared to '<\
<br />routinely create and distribute detailed topographic maps for virtually every community in the \\,
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<br />cOl!~JIYE jfhe costs associated with the creation of new base maps would have overshadowed the
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<br />~URNPIKE
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