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from pictures of the site. Cross sections for the HEC-iI program <br />• were taken from 5' contour interval topographic mapping at a scale <br /> of 1-inch = 100-feet. Table 2 is a summary of the output from the <br />HEC-II computer run. <br />Plate 2 (in pocket) shows the flood plain delineation of Trout <br />Creek for the area near Apex Mine #2. .The 100 year flood plain is <br />shown throughout and the 25 year and 10 year flood plains are added <br />where the hori2ontal spread is greater than five feet. The existing <br />fill is located between cross section 12 and 17 on the west bank. <br />A possible pre-fill flood plain line is also shown. This is <br /> <br />based on the assumption that the pre-fill flood plain was similar <br />to the flood plain upstream and downstream of the fill area. A <br />constriction has been created by the fill area, and subsequently, <br />an increase in velocities through the fill area can be noted in <br />• Table 2. While the velocities show increases up to 4 feet per <br />second through the constriction, these velocities are not unusually <br />high for the stream in its natural state. A list of the average <br />velocities at each section and other hydraulic data is given in <br />Table 2. <br />The effects of the constriction on land dr~anstream are minimal. <br />The depths and velocities downstream will be roughly the same as <br />i they would be without the constriction, However, there may be <br />some deposition of material for a few hundred feet downstream as <br />~ the flood plain widens and the velocities drop. upstream of the <br />constriction, ponding of up to 4' may occur against the fill em- <br />bankment and, in turn, cause greater depths upstream.. These <br />effects are not extensive and would only extend 300-400' upstream. <br />-s- 13`- <br />