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<br />ORAWING THE FLooDE'LAIN INUNDATION !1M'3 <br /> <br />using the best available topographic map for the stream below the dam (7.5 <br />minute u.S. geological survey maps are adequate), draw the floodplain map as <br />follows: <br /> <br />a. Starting at the dam and working downstream to the end <br />reach. draw a reference line down the center of the channel. <br />locations where the topographic map contours cross the stream <br />point on the reference line. <br /> <br />of the study <br />Find the <br />and mark each <br /> <br />b. Locate the end of all typical reaches along the stream and note flow <br />depths (oi) previously calculated and recorded in table III. <br /> <br />c. Calculate an interpolation factor (Ii) for the end of each typical <br />reach <br /> <br />Ii =....!tl.... <br />C.I. <br /> <br />Equation 17 <br /> <br />where C.I. is the contour interval of the map. <br /> <br />d. Measure the distance between the two points. where the contour lines <br />cross the stream above and below the end of each typical reach and designate <br />this distance xi. Starting at the point where the contour line crosses the <br />stream above, measure downstream a distance XiIi and place a dot on the <br />stream. <br /> <br />Steps a through d are shown in table IV and figure 11. <br /> TABLE IV <br /> FLOODPLAIN PLOTTING OATA <br /> Ii = ....!tl.... <br />LOCATION oi C.I. xi xiIi <br />At dam 18.8 0.94 2640 2482 <br />End of reach 1 17.3 0.87 2640 2297 <br />End of reach 2 5.4 0.27 10560 2851 <br />End of reach 3 8.1 0.41 5280 2165 <br /> <br />17 <br />