Flood peak attenuation modelling using source control BMPs / Fatheeyah Zainuddin

The expansions of urban centre areas are significantly causing the shrinkage of natural excess rainfall and runoff control systems. Natural vegetations are replaced with concrete surfaces which indirectly increase the impermeable areas, producing higher runoff and flow velocities that affect the existing settlements downstream. To cater the excess runoff volumes, the conventional drainage system suggest the rapid discharge method was adapted whereby the run off was drained fast from the urban areas into major drainage system before it could cause any flood damage. However, this approach has many drawbacks to drainage design including higher flood risks for downstream areas as well as excessive size of the drainage systems. This problem is faced by many communities, among them those settled in the Junjung River Basin which is the subject of this study. The basin is located in the State of Penang and has high potential to be developed in to an urban area in the near future. Thus, this thesis depicts a study conducted to cater the future developmental pressure to the drainage system by employing the Source Control Best Management Practice (SCBMP) as suggested in the Urban Stormwater Management Manual for Malaysia (DID, 2000). The main objective of this study was then, to reduce flood levels with applying one of the Best Management Practice method namely “detention pond” for peak flow attenuation. HEC-HMS and HEC-RAS, public domain software developed by the United States Army Corp of Engineers Hydrologic Center, were used for hydrologic and hydraulic modelling of the river basin and a 3.1 km study reach respectively. The river modelling configuration consists of on-line and off-line detention pond within the study area is significant in reducing flood level in Sg. Junjung for current condition. The result of this research also indicates that detention pond is an effective measure for flood peak attenuation for future development in Sg. Junjung but it must be complimented with minor channel improvement measures.