Hydrological Analysis on Semi-Urban and Urban Areas in Kajang

N.Azimah.Bahrum, M.A.Malek

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.