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<br />~~ 1988 THE PUBLIC RECORD CORPORATION <br />ALL RIGHTS RESERVED <br /> <br />~" <br /> <br />llCRI, 1.88 <br /> <br />Page 9 <br /> <br />1 evees, at confl uencer, with tri butari es, "nd at. 211 flow <br />control structures. In genera~, more cross sections are <br />needed to define energy losses in urban area, than in rural <br />areas, where steeper slopes are encountered, and on smaller <br />streams. Based on computed results, addit'onal cross <br />sections may be required if the slope of_the energy yrade <br />line between successjve cross sections decreases by more <br />than 50 percent or increases by more than 100 percent. The <br />location of the cress-sections shall be shown on the work <br />maps. <br /> <br />HaD Accuracv. Vertical map accuracy shall Dc ~uch that <br />at least 90 pettent ~f all contours are within 1/2 of the <br />contour interval, and the remaining contours are not in <br />error by more than 1 contour interv"l. Horizontal map <br />accuracy shall be such that at least 90 percent of the <br />planimetric features are plotted to within 1/40 inch as <br />measured at the map scale, and the nmaining features are <br />plotted to within 1/20 inch. <br /> <br />In areas where the ground is completely obscured by dense <br />brush or tree cover, contours shall be plotted as <br />accurately as pOSSible from the stereoscopic model, while <br />making full use of spot elevations obtained where the <br />ground is visible. Spot elevations shall have the same <br />vertical and horizontal tolerance as the contours. Where <br />appl icable, the work map shall carry the statement: "Thi s <br />map campl i es wi th Nat i anal Map A-ccuracy Standards." <br /> <br />B. Hydrologic Analysis <br /> <br />~. <br /> <br /> <br />8. <br /> <br />1. <br /> <br />Freouency. The hydrologic analysis <br />minimum, calculations for the 10-, <br /> <br />sha 11 <br />50-, <br /> <br />include, at a <br />and IOO.year <br /> <br /> <br />the peak discharge for the 500-year flood be calculated in <br />addition to the .other discharges. <br /> <br />2. Hethodolooy. Peak discharges developed from hydrologic <br />analysis for floodplain management purposes shall be <br />determined by one or more of the following methods <br />depending on the length of systematic records available: <br />statistical analysis or regional regression analysis of <br />stream gage data, including historic flood data: <br />comparisons with similar watersheds; or flood estimates <br />using hydrologic models and precipitation records <br />(synthetic analysiS). All available streamflow data from <br /> <br />THE CODE OF COLORADO REGULATIONS <br /> <br />2 CCR 408-1 <br />