Time of Concentration Estimated Using Some Methods and Application in The Ciliwung Watershed, Jakarta

Abstract

Flood is one of the disasters that must be faced in the lowlands with poor drainage system, when there is high rainfall. Rainfall in the that upstream River can affect water level downstream River. Calculation of river discharge and forecast from that time that arrival from flood can Help prepare population to face that disaster. That method used in this lesson is a quantitative method with analysis from rainfall and planned flood repatriate. Then, time of concentration (TC) before calculated use that time traveling method, That Experience Resource Conservation Serve (NRCS) and Kirpich. That results is compared to with HEC RAS and observation method. That research location is in Ciliwung watershed, with tc calculation of Katulampa (Bogor) to MT. Haryono (Jakarta). That results show that results from design flood discharge using the HSS Nakayasu method for Q2 of 161.04 m3/s, Q5 of 187.07 m3/s, Q 10 of 215.08 m3/s, Q25 of 263.11m3/s, Q50 of 308.91m3/s and Q100 of 364.34m3/s. Time of concentration using the Time Travel method from Katulampa to MT. Haryono 12 hours 32 minutes, while using the NRCS method is 12 hours and 31 minutes while the Kirpich method is 12 hours 52 minutes. That time of concentration using observations is about 13 hour and using the HEC RAS is 14 hours. The closest method to calculate the time of concentration under actual conditions is the Kirpich method.