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ABSTRACT
Urban drainage system in Malaysia is usually based on conventional
system made up of concrete drains which convey surface run-off from
rapid development urban areas. This conventional design could
increase sedimentation in the drains due to surface run-off which
carried along sand and soil particles into the drains. This
sedimentation will decrease the cross-sectional area of the drains
and slowly reduce the designed hydraulic capacity of the drains. The
incipient motion and sediment transport are influenced by water
velocity, particles sizes (d50), concentration of
suspended bed load (Cv) an other factors.
The objectives of the research are to establish the deposited
sediment particle size, to determine sediment deposition and
corresponding slope and also to evaluate the existing incipient
motion equations for self-cleansing design purposes.
The study conducted includes sampling works at Sg.Raja (10 stations)
and twelve cities of Peninsular Malaysia. Particles sizes
distribution analyses were carried out to determine particles sizes
for use in the existing incipient motion equations. The most
suitable equations can be determined to predict sediment deposition
occurred in the drains based on measured deposited sediment slope.
Based on particle size distribution analyses, the sediment average
size for twelve cities in Malaysia is 0.75mm while for Alor Star the
average sediment size is 0.93mm. The existing incipient motion
equation assessments show that Equation 2.19 (Novak & Nalluri, 1975)
is able to predict satisfactorily the sediment deposited slope while
Equation 2.27 (Ab.Ghani et al., 1975) is able to predict well the
design slope.
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