Determination of Flow Resistance in Modular Open Channel

Storage tank module is a lightweight modular system which commonly used as underground storage tank for rainwater harvesting. This storage tank module promotes reuse of rainwater, infiltration of surface water and water quality improvement. In sustainable stormwater drainage designed by River Engineering and Urban Drainage Research Centre (REDAC), Universiti Sains Malaysia (USM), this storage tank module was used as underground conveyance conduit integrated with grassed swale. There are two types of modular channel investigated in this study which is the existing and newly designed modular channel which is known as Modular Channel Type A and Modular Channel Type B respectively. In this study, a total number of 54 sets of experimental and field had been analyzed in order to investigate the hydraulic characteristics of Modular Channel Type A. Meanwhile, a total number of 30 sets of experimental tests were carried out in investigating flow in Modular Channel Type B. Investigation concerning the variation of Manning’s n with hydraulic parameters which include of flow depth, flow rate, Froude number and Reynolds number were also presented in this study. The analysis indicated that there were good correlations between Manning’s n and Froude number with correlation of coefficient (R₂) more than 0.93. A design step of modular channel was proposed by utilizing the relationship between Manning’s n and Froude number using iteration. Apart from this, simplified equations by using only aspect ratio and channel slope were developed by using multiple non-linear regression and genetic programming. It shows that prediction by using genetic programming tends to underestimate flow rate for field date. Information reported in this study can be used to estimate the hydraulic characteristics of modular under different condition.