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ABSTRACT
The presence of sediment deposits in a drainage system or rigid channels
as monsoon drains could produce flash flood. The ability of the
drainage system to erode sediment deposit will allow the system to carry
the designed discharge.
The
aims of the present study are to gain an improved understanding of the
incipient motion processes in urban drains and to provide improved
incipient motion relationships. This is achieved by
investigating the important parameters governing the incipient motion
of particles for several bed thicknesses.
In
the first part of the study, the characteristics of flow in a
rectangular cross section channel with different water flow depths and
various slopes were studied. A series of incipient motion experiments
were then carried out in a rectangular channel 300 mm wide and 10 m
long. Four different bed thicknesses (ts) were used
namely d50, 5 mm, 10 mm, and 24 mm utilizing sediment with
size between 0.55 mm and 4.78 mm. The sediments were collected
from existing drains in Ipoh City and Batu Gajah Town.
The
present data were utilized to appraise the existing incipient motion
criteria for rigid channels. The results show that the existing
equations are valid only for the case of bed having thickness equals
sediment size (d50) only.
New
incipient motion criteria applicable for various bed thicknesses were
then developed for 1% £
£
5% (h is the channel depth = 450 mm). These new equations could
be used to design new drainage systems with the ability to erode
deposited sediment.
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