ABSTRACT
Natural
channel morphology depends on the interaction between fluid flow and
the erodible materials in the channel boundary. Velocity is strongly
related to flow resistance, which is one of the most important
elements in the interaction between fluid flow and the channel
boundary. Computations involving flow in open channels commonly
require an evaluation of roughness characteristic of the channel. The
engineers have use a number of flow resistance equations involving
grain roughness, form roughness and a combination of both, but the
Manning’s equation has been widely used internationally for
predicting roughness values in natural channels.
In
river engineering, Manning’s roughness coefficient, n, has been used
widely in river hydraulic models. The procedure for selecting n values
is subjective and requires judgement and
skill that is developed primarily
through experience apart from knowing the factors that affect the
values of n. Since flow and the boundary roughness vary
with river conditions, a model of some form is to be developed for
evaluation of n values for rivers in Malaysia. This research has
been carried out at four rivers in the River Kinta Basin namely Pari
River, Raia River, Kampar River and Kinta River.
A
total of 122 data have been collected at six stations.
Evaluations on the existing equations show that none of the equations
has given a value of n which can predict satisfactorily the discharge
of a river.Two
new equations have been developed and found able to predict
satisfactorily the discharge of rivers in Malaysia. So the use of new
equations are recommended in determining the suitable value of n.
