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<br />cases the islanG W<lS nearly submerged Or created by a structure
<br />in the floodplain and not judged worthy of delineation, 'l'here-
<br />fore, on most cross-sections with divided flows only the
<br />extreme water surface limits are shown.
<br />
<br />The floodplain at the end of reach I, Hollywood Street, fills
<br />a large natural detention area, It was felt that using the
<br />storage volume output from the hydrology model would yield
<br />water surface elevation results as reliable as those obtained
<br />using the hydraulic progra~, The extreme upstream end of the
<br />floodplain in reach I is therefore drawn from S,W,M,M, output,
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<br />Two reaches which r~ceivcd scanty cross-section coverage and
<br />little computer modelling are the reach north of Vine Drive
<br />which parallels reach M, and reach X below the C & S railroad
<br />tracks. Both areas ar<o shown on Figure 6, These areas have
<br />~n common light development densities and large uncertainties
<br />in their inflow discha~ges due to modelling difficulties of
<br />diverc;",nt flows, In addition, reach X, including the city
<br />maintenancu building below the C ~ S tracks, has thp. probability
<br />of divergent flow pe>ttcrns itself, Beca",se of the inherent
<br />unc<'rtainti",,,. m\1ch great."r thlln th.. \1ncf)rtainti..~ att,>n,ling
<br />all the other rCilchc5, and because of the relatively low damage
<br />potential, a full scale hydraulic analysis in these areas was not
<br />conducted,
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<br /> TITLE TAeLE
<br />op~, FLOODPLAIN
<br /> ;"Of' ~< DATA TABLE 4
<br />
<br />Relatively more subjective assumptions were necessary to model
<br />the floodplilin for thoi' reach from the New ~le~cer Canal to the
<br />Poudre High School .rrigat~on pond, The dlvergent 100 year rlows
<br />in the vicinity of Poudrc High School flo'~' .;>cross a 1000 ft,
<br />section of LaPorte Avenue, yet the lower reach was modelled with
<br />two discrete in f 10\01 points. This res\.lltl'd in sam!' portionS being
<br />cons..rvatively :t1oC:elleu with ldrg~r flows thil.:1 '.rou~d actually ""cur,
<br />l\lSo, some overbank flew wo",ld bl' lost to the north just prior to
<br />no-aching t~le ~c,,' ~1crc"r Ca:1i1l. l'~H! difficuLty in !"<'solvinq the
<br />final outflov.' poi,..tof thOlt ~pillLl.';c, cOnbincd '.rith the fact that
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