الفهرس 
chapter 1Only 14 pages are availabe for public view
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Abstract
A spillway is a hydraulic structure that is usually provided at storage and
detention dams to release surplus or flood water that cannot be safely stored in
the reservoir. With a huge amount of water potential energy that converts to a
kinetic energy through the transfer from the large storage area to the narrow
basin. This high speed water flow is scouring the soil downstream the spillway
that affect the stability of the structure and change the river bed level. So this
study aims to decrease the scour downstream the spillway structure by
increasing the energy dissipation through the spillway body and the stilling
basin.
The study conducted by an experimental study for scour characteristics
downstream spillway. With different arrangements including slopped spillway,
stepped spillway, stepped spillway with half cylinder strips on steps and stepped
spillway with half cylinder strips on steps and inside stilling basin. All these
cases were tested with the same angle of conversion. from all cases, it was
found that the scour depth was decreasing with increasing number of spillway
steps to reach minimum scour depth at stepped spillway with three number of
steps. As energy dissipation was increasing, maximum scour depth was
decreasing. By using the half cylinder strips on 3-stepped spillway, the scour
depth was decreasing to reach minimum depth at relative strip height equal 0.34.
When we used the strips in the basin, it was found that every position in the
basin had best strip height. In case of relative position 0.09, the relative height
0.34 gave minimum scour depth. In case of relative position 0.22, the scour
depth was minimum at relative strip height equals 0.19. Also, relative strip
height 0.19 was the best in case of relative position 0.35 and 0.53.
In addition a statistical regression study which had been performed and a
good agreement was obtained between the experimental data and statistical
models. Finally, the results of this study may be recommended in the field of
applications
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