FLOOD09478 - Laserfiche WebLink

Home Browse Search

program flEC-2 "'lI~t""r Surfllce Prof lies". These computo/lt!ons ..ere b~~ upon chennel end flood pl~ln condItions ~s represenTed by surveys conducted lr\ the sprl ng of 1974 ~r\d deto/l co) lected from the South Plette RI~er flood of r~y 1973. The locetlon of each cross section Is shown on the flooded &rea pletes. 'lIater surfece profl!es for the lO-y&er, 50-ye...r, 1 Oo-yeo/lr , end 500-yeer floods were de~eloped for reaches of the South Platt"" Rlv.r loceted In th"" vicinity of 6rlghton, Fort Lupton, Plettevllle, EVllns, Greeley, Le S...lle, Kersey, end Orchard. Th""59 profiles elso ~ high Rtflr IMrks for the M...y 1973 flood IInd .II COOIIJluted wat.,... surfece profile which represents that flood. This ~uted 1973 flood profile Is based upon the observed high water merks shown and Is a "best fit" profile. Elevatlon-dlsctlarge curves showing the 10-year, 50-year, 100-year, and 500-year floods are also pre- sented. These curves ere loc...ted ...t the surveyed cross sections Which were not used In computing weter surfece profiles. The dete present.c by these curves Is b~sed upOn reletlonshlps developed f~ physlcel cherecterlstlcs of the respective cross section end 1973 flood det.... ~ detelled study mey show slgnlflcently different nilsults. The floodec:l l'lreapletes show photographs of tne flood of May 1973 a~ en outline of that flood. The location of observed high "dter ~rks from that flood ar@ elso shown. A channel centerline end chennel stationing Is provld@d In those arees In which waTer surface profiles are provided. This centerline and 5t...tloolng does not nacess...r1ly lodlc...hl th9 actu~! stre;::"'. center! InoJ but Is used only for purposes of referen~e. These plates alSO show the limits of the lOO-yesr end 50a-year floods at each cross sectIon as deter- ..Ined from tl\e water :ourhc8 proHles or elevatlon-<llscharge curves. Tne loelltlon of these flood limits et points between the cross sections where water surface profl!es ere presented can ~ deter- mined by selecting the proper water surface elevation f~ t~e water surfaee profIles and establishIng that point on the flood plain by survey. Slm!larly, flood characteristics at points between cross sectIons where water surface profiles are not pr@sented can be estI- mated by noting the elevatIon dIfferences between the desired flood IInd the 1973 flood On the elevation-discharge curves and applying these relationships to the flood Cheracterlstlcs as viewed on the 197J aerial photos at the desired looetlon. U. S. Geological Survey quadrangle maps orovlde veluable Information for transferring rela- tionships. " "