Tech. J. River Res. Inst. 13(1): 87-101, 2016 (October), ISSN: 1606-9277 1 Chairman, Center for River, Harbor & Landslide Research (CRHLSR) and Professor, Department of Civil Engineering, Chittagong University of Engineering & Technology (CUET) Chittagong 4349, Bangladesh, Email: aysha_akter@cuet.ac.bd; aysha_akter@yahoo.com 2 Research Assistant, CRHLSR, Chittagong 4349, Bangladesh ESTIMATING URBAN FLOOD HAZARD ZONES USING SWMM IN CHITTAGONG CITY Aysha Akter 1 and Ahad Hasan Tanim 2 Abstract Identifying urban flood-prone areas with their relative hazard scale is the fundamental work of urban flood management. This may introduce using a probabilistic methodology by flood hazard zoning of potential urban flood hazard area. Based on statistical analysis of US EPA Storm Water Management Model (SWMM) with a threshold value of maximum depth of each node of link network number of overflow events in a specified time period can be obtained. Further using Kernel hazard density the spatial analysis in ArcGIS can be used to obtain a GIS compatible maps for the hazard zoning of the potentially flood prone areas. In this study Chittagong city, the second largest city of Bangladesh has been taken as a case study and the wettest year 2014 was selected for model simulation. The validated model outcome reasonably identified the flood prone vulnerable zones which is comparable to the outcome of recent field studies. Thus, it is expected that the acquired flood hazard mapping will play major role once this is observed using details field data. Finally, this would provide flood risk information to the decision makers and flood protection works to prioritize the relatively more flood hazard zone for management purpose. Introduction Chittagong city area has experienced the highest number of flood incidence in last decades. Social environment, local economy and ecology have been hampered and degraded due to prolonged urban flooding. During the flood about 7 million city dwellers face severe disruption in their daily life (CWASA 2015). The overflow in the drainage system frequently occurred due to combined effect of heavy rainfall as well as tidal effects. Attempts have been made by frequent dredging of the drainage systems without any comprehensive study of flood. As a result overall flood protection works fail to offer the expected supports. More than 2.73 Billion Bangladeshi Taka has already been employed by the Chittagong Development Authority (CDA) during last decades but the overall flood protection work faces difficulties to provide permanent protection to the adjacent city dwellers. Including Chittagong Water Supply and Sewerage Authority (CWASA) project based study, there were few research studies identified the key issues, i.e., heavy rainfall, tidal effect of adjacent Karnafuli River, intervention in sewerage system due to solid waste blockage as well as climate change (CWASA2015; Table 1). Thus, while analyzing the flood risk hazard those factors must be considered in addition the idiosyncratic topography of the area.