Determine the magnitude of the contraction scour depth given the following information about the channel and bridge:
(a) The upstream channel width = 322-ft; depth = 8.6-ft
(b) Q = 27,300 ft3/sec
(c) Channel slope = 0.004-ft/ft
(c) Bridge abutments consist of vertical walls with wingwalls, width = 122-ft; with three sets of piers consisting of 3 columns 15-inches in diameter
(e) The bed material size: the D50 = 0.0023-ft with a fall velocity = 0.33-ft/sec
(f) Original depth at bridge is estimated as 7.1-ft (Ans: ys = 10.1-ft)
discharge, Q1 = 27300 ft^3/s
Width, W1 = 322 ft
Depth, y1 = 8.6 ft
Area, A1 = W1*y1
velocity, V1 = Q1/A1 = Q1/(W1*y1) = 27300/(322*8.6) = 9.86 ft/s
Threshold velocity, Vt = Ku * y1^(1/6) * D50^(1/3)
D50 = ...
Corresponding to a given channel specifications, scour depth (ys) is estimated.