A method is presented for esimtating clear-water contraction scour and abutment scour at bridges. The method is based on the procedure developed by Neill (3) for computing competent velocity-the critical flow velocity which causes the incipient motion of bed particles. Meill presents a set of competnet velocity curves based on flow depth, velocity and size of bed maerial. The critical flow velocity of various sizes of oncohesive materials has been reported by Shield (1) and others(2).
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