International Journal of New Technology and Research (IJNTR) ISSN:2454-4116, Volume-2, Issue-1, January 2016 Pages 58-66 58 www.ijntr.org Abstract— Flooding is a natural phenomenon occurred mainly due to heavy rain and improper water resources planning. It is one of the serious natural hazards that may cause damage to human lives, agriculture, environment and structures. This study focuses on the establishment of the latest trending on intensity duration frequency (IDF) curves and determination of various hydrological parameters such as curve number (CN), hydrograph peak time (t p ), time of concentration (t c ) and manning’s roughness coefficient (n) for urban and semi-urban areas in Kajang, Selangor, Malaysia. 25 years of rainfall data from 1990 to 2014, obtained from the Department of Irrigation and Drainage (DID), Malaysia were used in this study. Moreover, the temporal pattern in this study is built of 15 minutes, 30 minutes, 60 minutes, 120 minutes, 180 minutes, 360 minutes, 720 minutes and 1440 minutes. Results from this study exhibited the new established IDF curves developed for Kajang at both semi-urban and urban areas for Sg. Jelok sub-catchment. Based on the calculations conducted, it is found that although the urban areas has a larger value of time of concentration, t c at 12.98 hour and highest value of hydrograph peak time, t p at 0.87 hour, various flooding events are still occurring in several places in the urban areas. These flooding are probably still occurring due to the current active residential constructions and on-going constructions of elevated inner city train (LRT) in addition to the old drainage system still used in the urban areas of Kajang that hinder the flow of surface runoff. Index Terms— Intensity Duration Frequency (IDF), hydrological parameters, urban, semi-urban areas, flooding. I. INTRODUCTION Meteorology, physical characteristics and land use exercise significant influences to the hydrology characteristics of an area [1]. One difference in any of the characteristics between the two sub-catchments will result in a different behavior of their hydrology. Therefore, it is important to discuss the differences between semi-urban and urban areas as presented in this paper. Large developments in urban areas of Malaysia have increased the percentage of impervious surfaces, resulting in a large amount of surface runoff. In addition, inadequate drainage facilities have also contributed to the short term floods namely flash floods occurring in urban areas [2]. These disturbing scenarios served as a statement of problem in this study. Researchers and other scholars worldwide have also taken initiatives to conduct studies specifically to reduce Nur Azimah Binti Bahrum, Department of Civil Engineering, College of Engineering, Universiti Tenaga Nasional, 43000, Selangor, Malaysia. Marlinda Binti Abdul Malek, Assoc. Prof. Ir. Dr., Department of Civil Engineering, College of Engineering, Universiti Tenaga Nasional, 43000, Selangor, Malaysia the negative effects of urban runoff and improving the local conditions [3], [4] and [14]. In the last decade, issues on flooding and storm water pollutions have risen in Malaysia. It was identified as major environmental impacts of urban development on storm water, discussed since the late 1970s due to widespread occurrence of flash floods, especially in Kajang. Nowadays, awareness on the importance of hydrology, as a branch of natural science has arisen. It includes assessment, development, utilization and management of water resources. This phenomenon can be proved with hard work in hydrology education, research, development and analytical techniques for global hydrological information collection [1]. There are several flood events recorded within Kajang town in the recent years especially in 2008, 2011 and 2012. Kajang experienced one of its worst flash floods in October 2008, submerging nearly two-thirds of the town. The flood level is between 0.5m to 1.5m and brought traffics to a standstill in many parts of the town. Disaster seemed certain with Langat River and its tributary Jelok River threatening to burst their banks after just an hour of rain [5]. Jelok River is one of the main tributaries of Langat River. It flows from the upstream of Kajang Prison and finally flows to Langat River at the downstream through Kajang town at the length of 9 km. The total catchment area of Jelok River is about 1765 hectares. The rapid development at the upstream of the river especially the on-going residential projects have increase the water runoff during heavy rains which caused flooding at the downstream of the river in Kajang town. Hence, the scope of works in this study includes hydrological analysis such as double mass curves, intensity duration frequency (IDF) curves and temporal pattern were conducted at both the semi-urban and urban areas of Kajang. Comparison between semi-urban and urban areas will then be established. I. STUDY SITE AND METHODOLOGY The study area is located in Kajang, a town in the eastern part of Selangor, Malaysia. Due to data availability, one (1) rainfall station has been selected to represent the rainfall pattern of the area. The selected station is RTM Kajang station for Jelok River sub-catchment. In this study, Jelok River sub-catchment is further divided into two (2) smaller sub-catchments namely Kajang Prison (semi urban) and Kajang town (urban) areas. 25 years of rainfall data from 1990 to 2014 obtained from the Department of Irrigation and Drainage (DID), Malaysia were used. Fig. 1 shows the Jelok River sub- catchment. Hydrological Analysis on Semi-Urban and Urban Areas in Kajang N.Azimah.Bahrum, M.A.Malek