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EXISTING SWALE IN SUBWATERSHED NUMBER 31 <br />Six subwatersheds empty into the existing Swale located in subwatershed 31. The total <br />amount and rate of flow routed through this Swale during a 10-year, 24-hour storm <br />event into segment 032 of Ditch #3 has been calculated using the TR-20 computer <br />program. Below is a summary of pertinent ditch and watershed data. Exhibit D is a <br />map depicting the reclaimed area being described. <br />TABLE 1 <br />EXISTING SWALE DATA <br />Point of Confluence <br />for the flows of <br />the Six subwatersheds <br />Station 10+60 of Ditch #3 <br /> Manning's <br />Design Bottom Roughness Flow Flow <br />Discharge Slope Coefficient Depth Velocity <br />(cfs) (Ft/Ft) (n) (Ft) (FPS) <br />20.47 0.0104 0.030 0.27 2.03 <br />TABLE 2 <br />SUBWATERSHED DATA FOR EXISTING SWALE <br /> Drainage Change in Length of Time of <br />Subbasin Area Elevation Drainage Concentration <br />Number (Ac) (Ft) (Ft) (Tc, Hrs*) CN <br />121 19.09 126.0 2531.25 0.1695 79.0 <br />122 7.72 62.5 2659.66 0.2342 79.0 <br />123 3.37 167.5 1424.58 0.0786 79.0 <br />124 8.14 72.0 1660.00 0.1291 79.0 <br />125 6.34 46.0 692.78 0.0560 79.0 <br />31 15.64 103.0 1077.33 0.0685 79.0 <br />* Tc = L 1.15 Where: L = Length of watershed in feet <br /> 700 $ <br />7 H = Change in elevation from the highest point <br /> , in the watershed to point confluence of the <br /> watershed drainage <br />The dimensions of the channel, through which these flows were routed in subwatershed <br />31 were taken directly from Exhibit D. Due to the low velocities and shallow flow <br />depths, no rip rap will be required in this area. <br />Existing terraces also shown on Exhibit D direct flows around the former proposed 3rd <br />segment of Ditch #3 (Sta. 10+60 to 15+00), therefore, nullifying the need for this <br />segment of the ditch. <br />