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Abstract
DROP structures are widely used in open channels. Downstream the DROP,
sudden change from position energy takes place. Also, hydraulic jumps, high
turbulence, and air entrainment occur as the flow changes from supercritical
just downstream the DROP to subcritical at the tail section. Scour hole is formed
in the movable bed due to all these changes in flow characteristics resulting in
big increase in bed shear. A laboratory experimental study was conducted to
examine the effect of time, flow parameters and the DROP slope on the scour
hole dimensions. The dimensions under study are the maximum scour depth,
the length of the scour hole, and the scoured volume.
Four DROP slopes were examined S= 0:1, 1:1, 2:1, and 3:1. Soil concrete apron
was constructed on the low level downstream the DROP. Also, a case with no
DROP was used for the purpose of comparison. The resulting data was discussed
through figures and statistical equations using hydraulic principles
Statistical equations relating the scour parameters (depth, length, and volume)
to time were concluded, and were found to be in a logarithmic form. It was
concluded that the maximum relative depth of scour increases as the DROP slope
gets milder, while relative length of scour and relative volume of scour increase
as the slope gets steeper.