Rivers 2011 6 th – 9 th December 2011, Penang, Malaysia 266 Determination of manning’s n for subsurface modular channel LI CHOO KEE, MSc Student, River Engineering and Urban Drainage Research Centre (REDAC), Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300 Nibong Tebal, Penang, Malaysia. Email: choochoo07@gmail.com NOR AZAZI ZAKARIA, Professor & Director, REDAC, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300 Nibong Tebal, Penang, Malaysia. Email: redac01@eng.usm.my TZE LIANG LAU, Senior Lecturer, School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300 Nibong Tebal, Penang, Malaysia. Email: celau@eng.usm.my CHUN KIAT CHANG, Science Officer, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300 Nibong Tebal, Penang, Malaysia. Email: redac10@eng.usm.my AMINUDDIN AB. GHANI, Professor &Deputy Director, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300 Nibong Tebal, Penang, Malaysia. Email: redac02@eng.usm.my ABSTRACT This paper describes the laboratory test of a newly designed module used as subsurface conveyance system to provide better enhancement toward best stormwater management system. Three types of modular channel were tested in the laboratory at three different slopes. Data collected in these experiments include temperature, flow depth and flow velocity. In this paper, the hydraulic characteristics and Manning’s n for this newly designed modular channel have been experimentally studied. Suitable equations in governing the Manning’s n for this modular channel have been developed. Keywords: Modular channel; Manning’s n; hydraulic characteristics; regression analysis; genetic programming 1 Introduction Modular tank or simply known as module is applied as rainwater harvesting system where rainwater will go through infiltration and filtration process to collect clean, clear and odorless water for various purposes. The other applications of modular tank in stormwater management include on site detention, filtration pond, bio-remediation and etc. In Malaysia, the application of modular channel as subsurface conveyance conduit has been applied in the Bio-ecological Drainage System (BIOECODS) in USM Engineering Campus (Zakaria et al., 2003; Ab. Ghani et al., 2004) and sustainable urban drainage system in Taiping Health Clinic completed in year 2005 (Ab. Ghani et al., 2008). The subsurface modular tank applied in BIOECODS is shown in Figure 1 while the modular tank applied in Taiping Health Clinic is shown in Figure 2. Modular tank applied in BIOECODS and Taiping Health Clinic has high roughness which provides flow attenuation. However, this roughness is not suitable for the design as conveyanve system because it causes problem such as localize water ponding as the stormwater flow is slower than the stormwater infiltration rate into modular tank. Figure 1 Subsurface modular tank with dimension 405 mm x 465 mm x 607 mm Figure 2 Subsurface modular tank with dimension 410 mm x 450 mm x 685 mm