Bridge scour, 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)