SEDIMENTATION TRANSPORT AND DESIGN OFCHANNELS
In a channel bed made of fine sand, when the velocity is gradually increased, the sequence of bed formation is—saw-tooth ripples-dunes with ripples-dunes-flat surface sand waves and anti-dunes. * When a few particles on the bed just start moving, the condition is known as critical condition. * A regime channel or a stable channel is one in which neither silting nor scouring takes place. * Critical velocity in a channel is the mean velocity which will just keep the channel free from silting or scouring. * Kennedy formula for critical velocity is Vo = 0.55 m y 0.64. where y = depth of flow m = critical velocity ratio Lacy differentiated between true regime, initial regime and final regime. * According to Lacy 1. Natural silt transporting channels have a tendency to assume a semi-elliptic section. 2. The coarser the silt, the flatter is the semi-ellipse. 3. Silt factor f is given by f = where V is in m/sec and R hydraulic mean depth in m. 4. Wetted perimeter P = where Q is discharge in m3...