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<br />c. Hydraulics <br />Hydraulic analyses conducted in this study were done using the U.S. <br />Army Corps of Engineers computer model HEC-RAS (River Analysis <br />System). The average watershed slope in the study reach is 4 to 6 <br />percent; therefore, subcritical flow conditions prevail through all <br />study reaches. <br /> <br />Discharge values were discussed in the hydrology section of this <br />report. Most of the cross-section data were chosen from <br />topographic maps with a scale of 1 cm = 20 meter with 0.25-meter <br />contour intervals. Dimensions of bridges and hydraulic roughness <br />coefficients (n-values) were determined from field investigations. <br />Tables l(a) and (b) show the estimated n-values for HEC-RAS cross- <br />sections of West and East Douglas Washes. <br /> <br />Table 1(a) - Estimated n-values for West Douglas Wash's Channel Cross-Sections <br />HEC-RAS n-Values <br />Cross-Sections Left Over-Bank Channel Right Over-Bank <br />458-445 0.040 0.040 0.040 <br />440-405 0.050 0.050 0.050 <br />400-335 0.055 0.055 0.055 <br />325-320 0.030 0.030 0.030 <br />310-263 0.055 0.055 0.055 <br />260 0.065 0.065 0.065 <br />255-232 0.055 0.055 0.055 <br />230-200 0.060 0.060 0.060 <br />190-180 0.065 0.065 0.065 <br />170-130 0.050 0.050 0.050 <br />120-100 0.080 0.080 0.080 <br />4520-4460 0.040 0.040 0.040 <br />6457.5-6457.1 0.040 0.040 0.040 <br /> <br />8 <br /> <br />II <br />I <br />I <br />Ii <br />I <br />I, <br />I <br />I <br />,i <br /> <br />I <br />I' <br />I <br />I <br />I <br />I, <br />Ii <br />II <br />I <br />, <br /> <br /> <br />I <br />I! <br />