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<br />elevations for tile 10-, 50-, 100-. and500-year flood events at selected <br />reference points, for the reach of the Arkansas River from the upstream <br />Canon City corporate limits to Minnequa Dam (Appendix II). <br /> <br />elevations and general location of thebencmarks and control mark ersare <br />listed in Table 6. Additional survey notes and monument descriptions are <br />available for review at the ColoradO Water Conservation Board. <br /> <br />Flooded Areas <br /> <br />As indicated, the IOO-year frequency flood has been selected by the State <br />of Colorado as the flood event to be used for floodplain delineation and <br />regulation. The flooded area plates show the boundary of the lOO-year <br />floodplain. Since the base map for the flooded area plates isa two-foot <br />contour map, the outl ines of the other fl ood events, 10~, 50-, and <br />SOO-year, can be readily plotted using the information in Tables 5-1 and <br />5-11. <br /> <br />The f1oodelevations have been estimated by using surveyed channel cross- <br />sections and detailed topographic mapping. The hydrau1fcmodel (HEC-2l, <br />assumes that the hydraulic sections such as the natural channel, channels <br />fOmledby dllc:es or levees, bridges, culverts and dams will not change due <br />to effects of erosion, sedimentation or debris bloclc:age. Assumptionsmade <br />in this study are presented in the Technical Addendum of this report. <br />The area delineated on the flooded area plates as thelOO-year floodplain <br />meets the requirements of H.B. 1041 as an ar!!a of state interest. Also, <br />upon official approval by the Colorado Water Cons!!rvation Board, the area <br />outlined by the 100-year flood boundary will be designated as floodplain <br />area and may be regulated accordingly by tile local officials. <br /> <br />Flood Elevations <br /> <br />Flood cr"st elevations for the 10-, 50-, 100-, andSOO-year floods may be <br />found in Tables 5-1 and 5-11 of this report (the Flood Frequency-El evation <br />and Oischarge Oata tables). Th" f100ded area maps presented in Appendices <br />I and lI,give thl' plan viI''' nf thl' flOOded area on a contour base map and <br />the hiqh water "levations for the lOO-year flool1 can be ir'ltl'rpolat~11 from <br />thi s. The flood pro fil es, show the streambed 1'1 eva ti on s ~nd 1'1 e~ations for <br />the 10-, 50-, 100-, and500-year frequency floods. <br />The flood profil"smay be used in areas where controversy arises over the <br />lOO-y"arfloodboundary shown on the flooded area plates. Since the flood <br />profile plates give the el"vations and distance, or stationing, from a <br />knO\<;ll point, the high water elevations can be surv"y"d on tll" ground to <br />alleviate any discrepancies on the base map. <br /> <br />Ijori~ontal control us~1 f<;or ",appi~9 is bHed cr. Cclcr~dc State ~1~~C' <br />Coordinate System South Zone 1929 USC&GS Sea Level DatlJ/Tl. <br /> <br />Control Markers <br /> <br />In order to locate points on the ground relatjng to information given in <br />this report, fourbencmarks set by federal agencies havebl'en identified <br />in the study area. These bencmarks ar" tied to United Stated Coast and <br />G"odeticSurveyLjne25. The Fremont County control markers are brass caps <br />Sl't ir'l coneret". The location of all benc~arks and control markers are <br />shown on the tnpogrol;phic maps prepar"d for this study. The coordinates, <br /> <br />23 <br /> <br />14 <br />