International Conference on Water Resources (ICWR 2009) "Flow Pattern and Hydraulic Characteristic for Subsurface Drainage Module"

Grassed swales are low-cost storm-water best management practices (BMPs) which have been used extensively to reduce the peak flow of surface runoff, remove runoff pollutants by vegetation filtration as well as to enhance the groundwater recharge. Grassed swale system in Engineering Campus, Universiti Sains Malaysia (USM) is a part of Bio-Ecological Drainage System (BIOECODS) which usually being known as ecological swale. This ecological swale for BIOECODS is a dual drainage system which consist a surface swale and a subsurface drainage module in parallel arrangement. The subsurface drainage module is overlaid by a layer of porous media and a layer of top soil. A new drainage module has been produced with different pattern and internal structure recently. Apart from this, the porous media mentioned aboved which formed from clean river sand is being replaced by gravel in this current time. In previous study, the flow pattern inside the subsurface module is observed to be interesting as the flow varied between open channel flow and pipe flow. Further investigation for the flow pattern and hydraulic characteristic by subsurface drainage modules will be carried out in this study by conducting laboratory experiment under different discharge and slope conditions. Both of the pre-existing and the latest drainage modules will be evaluated. This paper discusses about the related studies, methodologies, and expected outcomes of this research. Result from this research is important in efficiency evaluation of ecological swale with subsurface drainage thus to provide information for future design of this dual drainage system. Keyword: BIOECODS; subsurface drainage module; flow pattern; hydraulic characteristic