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II. Multiple Channel Region Within the multiple channel region, discharges, Q (in cubic feet per second), that correspond to the various depth zone boudaries may be calculated by iteratively solving the following equation: D = 0.0917 n.6S-.3Q.36 + 0.001426 n1.2 S.6 Q.48 whcre D is the total depth in feet due to pressure head and velocity head, S is the fan slope, and n is Manning's roughness coefficient for the alluvial fan flood channel. Discharges, Q (in cubic feet per second), that correspon to the various velocity zone boundarics should be calculatcd using the equation: Q 99314 n4.17 S-1.25 V4.l7 C-16 where V is velocity in feet pcr second and S is the fan slope. Depth zones and velocity are designated from zone boundaries in the same manner as shown in the analysis for the single channel region. f. Compute Fan Widths for Zone Boundarics The fan widths (i.e., arc lengths from one lateral limit of the fan to the other taken parallel to contours) that correspond to each upper and lower zone boundary depth and velocity listed in Section 4e should be computed both for the single channel region and the multiple channel region. The following formulas should be used: I. Single Channel Region Fan Width = 950ACP II. Multiple Channel Region Fan Width = 3610ACP In the above two formulas, A is the avulsion coefficient, C is the transformation constant, and P is the probability of the discharge that corresponds to each given depth and veloc- ity. An avulsion coefficient (factor) greater than I should be selected by the Study Contractor in consultation with the PO. A factor of 1.5 is recommended in the absence of other data. In summary, the steps for the determination of the flood velocity and depth boundaries arc listed as follows: I. Compute all flood depth and velocity zone boundaries by the standard single channel method.