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<br />I <br /> <br />Table 7.7 Shield's parameter calibration <br /> <br />, <br />J <br />I <br />I <br /> <br />Cross-Section Area Wetted Hydraulic Bed Maximum Maximum Friction Calculated <br /> (sq ft) Perimeter Radius (ft) Shear Particle Particle ~~ape Dimensionless <br /> Iftl (asft Diameter lin\ Diameter (ft) fl/fl) Shield's Parameter <br />AR.O Total 65.1 54.82 1.19 0.7669 2.00 0.17 0,01035 0.045 <br />AR-O Total 65.1 54.82 1,19 0,7669 3.00 0.25 0.01035 0.030 <br />AR-O Thalweg 38.8 22.09 1.76 1.1344 2.00 0.17 0,01035 0.066 <br />AR-O Thalweg 38.8 22.09 1.76 1.1344 3,00 0.25 0,01035 0.044 <br />Shield's Parameter Average 0.046 <br /> <br />Table 7.8 Shield's parameter comparisons <br /> <br />Cross- Date Shield's Shear (psn Sediment Size Sediment Size Sediment Size % Gradation <br />Section Parameter (ft) (in) (mm\ <br />AR-O 7/1/98 0.030 0,767 0,25 2.98 75.69 100 <br />AR.O 7/1198 0.047 0.767 0.17 1,99 50,55 100 <br />AR.O 7/17/98 0.030 0.465 0.15 1.81 45.87 100 <br />AR-O 7/17/98 0.047 0.465 0.10 1.20 48.29 100 <br />AR-l0 5129/98 0.030 1.500 0.49 5.83 147.96 100 <br />AR-10 5129/98 0.047 1.500 0,31 3.72 94.44 100 <br />AR-10 7/17/98 0,030 0.735 0.24 2.85 72. 50 100 <br />AR.l0 7/17/98 0.047 0,735 0.15 1,82 46.28 100 <br />AR-20 5129/98 0.030 0.830 0.27 3.22 81.87 100 <br />AR.20 5/29/98 0.047 0,830 0.17 2,06 52.26 100 <br />AR-20 7/1198 0.030 1,010 0,33 3.92 99.63 100 <br />AR-20 711198 0.047 1.010 0,21 2,50 63.59 100 <br />AR,20 7/17/98 0,030 0.768 0.25 2,98 75.73 100 <br />AR-20 7117/98 0.047 0.768 0.16 1.90 48,34 100 <br /> <br />7.4.2. Reach Average Incipient Motion Results and Analysis <br /> <br />For the purposes of this study, sediment transport characteristics, including incipient <br />motion, were described on a reach average basis. Primary components of incipient <br />motion include a range of discharge hydrology, channel hydraulics, and incipient motion <br />equations. The range of hydrologic events are chosen to represent flows used as input to <br />the hydraulic model for determination of parameters necessary for calculation of incipient <br />motion equations. Particle diameters were then calculated for each cross-section within a <br />reach using Equation 7.4, The hydraulic model provided channel shear stress ('c) values, <br />Shield's Parameter (F*) was selected as 0.046, and the submerged unit weight of <br />sediment (Ys) was equal to 103 pcf. Site averaged maximum particle sizes in motion for <br />each particular flow rate were calculated by removing maximum and minimum <br />calculated values and then averaging all remaining values. Figure 7.7 and Table 7.9 <br />summarize incipient motion characteristics for each of the six sites at nine different <br /> <br />May 7, 1999 <br /> <br />Fluvial Geomorphological Assessment <br />Upper Arkansas River <br /> <br />Page 67 <br />