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<br />. <br /> <br />. <br /> <br />. <br /> <br />Hydraulic Analysis of Proposed Conditions <br /> <br />5 <br /> <br />;-. <br />, <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />, <br /> <br />c <br /> <br /> <br />, <br />,,' <br />145760 <br /> <br />Nt <br /> <br /> <br />.,.. <br />, <br />, <br />, <br />, <br />, <br />, <br />, <br />, <br />, <br />, <br />, <br />, <br />, <br />, <br />, <br /> <br />,,/ <br /> <br />, <br />, <br /> <br />-' <br /> <br />Lake area = 34 acres <br /> <br />0200 400 600 Bll lClXI <br />111111111+1 <br />SCALE (feel) <br /> <br />, ~~ <br /> <br />" 136450 __ _-"~ <br />" L FIS cross sectioN <br />... <br /> <br />13%90 <br /> <br />Section related area = 119 acre. <br /> <br />Figure 4. Areas Used In Roughness Calculations <br /> <br />been considerable weed growth occupying the lake area. "Open Channel Hydmulics" by Ven Te <br />Chow (page 113), gives a roughness of 0.05 to 0.07 for scattered brush and heavy weeds in flood <br />plains. This means that the area weighted roughness approach will be reasonably accurate. In <br />computing the new roughness for cross section #139690, we have <br /> <br />n = 0.Q2 x 34 + 0.062 x (119 - 34) = 0,050 <br />119 <br /> <br />This section will utilize I;he HEC-2 water surface profile program to analyze the proposed con- <br />ditions at Laku Landing. First, a simulation will be run showing the drop in water surfaces and <br />increase in flow velocities caused by the presence of the lakes during the occurrence of a base flood <br />discharge. Then, a method of topography change will be introduced which will return the water <br />surface to their original levels which existed at the time of the current FIS study. <br /> <br />Flood Level Analysis Due To Reduced Roughness <br /> <br />As previously stated, the construction of two lakes at Laku Landing since the current FIS will <br />reduce the roughness associated with cross section #139690. The existing roughness coefficient of <br />