Title: ANALISIS BANJIR MENGGUNAKAN SOFTWARE HEC-RAS 4.1 (Studi kasus sub DAS Cisimeut hilir HM 0+00 Sampai dengan HM 69+00 )
Abstract: The river is one of the many water resources that are utilized to fill the needs of raw water, so its presence is very important in supporting human needs.Along with the conditions changing in the river, the changing of land function system and population growth make the river is not functioning optimally as it should, it is resulting in many losses to the community.Floods can also damage buildings, farmland, infrastructure, the environment and damage the livelihood of the people in Banten, especially in the SUB-DAS Cisimeut.Flood occurs because of the overflow of the river and reduction of water infiltration areas.This study aims to know the cause of floods in the Lebak District, which is based on capacity with water discharge that occurs.Based on flood problems that occur, it can provide alternative solutions and determine capability of the condition of DAS Cisimeut downstream segment to accommodate the discharge of river flow for 50 years period.In this study, the data that is used is secondary data in the form of daily rainfall for 189 years and the cross-sectional dimension data SUB-DAS Cisimeut.Calculation Results of plan-rain with return period of 50 years is 128.26 mm, rain hourly with ABM method (Alternati block method), has 6 hours duration with the peak duration on third hour is 69.96 mm, while the discharge plan with Snyder method obtained the value of peak discharge is 1566.439m3 / s, while using the SCS obtained the value of peak discharge is 1217.22 m3 / s.The next calculation used software to determine the carrying capacity of the river, after being analyzed using steady flow and unsteady flow.SUB-DAS Cisimeut can not accommodate the flow rates that occur, hence the need for the normalization of rivers or other alternatives so that the water flow can be accommodated by the Cisimeut river.