### Determination of Manning’s Flow Resistance Coefficient for Kinta River Basin

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.