STUDY OF FLOOD HAZARD IN LOWER CITARUM RIVER WEST JAVA PROVINCE

• Main Author: Alfadhila Permana, Salsa
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/83926
• Institution: Institut Teknologi Bandung

The Citarum River is designated as a national strategic river area based on Presidential Decree of the Republic of Indonesia Number 12 of 2012 with the code WS: 02.06.A3 which is located in the administrative area of West Java Province. Part of the Citarum River, Lower Citarum, starts from the discharge of the Jatiluhur Reservoir, Purwakarta to the estuary at Muara Gembong, Bekasi Regency. The problem of water damage in the Lower Citarum River is quite high because one of the tributaries, the Cibeet River with a watershed area of 915 km2, always has the potential to send large discharges during high rainfall intensity. In this study, the modeling boundaries start from the confluence of the Lower Citarum River with the Cibeet River to the downstream section located in Muara Gembong, Bekasi Regency. With the input discharge in the upstream section, namely the operational discharge of the Walahar Dam at a steady rate of 400 m3/s and the input of the Cibeet Watershed with a discharge scenario of various return periods, namely 2 years with Qp = 1151.9 m3/s; 5 years with Qp = 1650.9 m3/s; 10 years with Qp = 20773 m3/s; 25 years with Qp = 3324.5 m3/s; 50 years with Qp = 3661.9 m3/s. In addition, there is input of lateral inflow discharge or flow of small rivers along the Citarum River with a total of 66 lateral inflows using the rational method. For input in the downstream section, tidal conditions are taken into account using the average water level with an average amplitude value of 1.2 meter and is included in the mixed tidal type tending to single daily. The estuary of the north coast of Java is included in the category of shallow sea waters. In this study, ananalysis of the flood event that occurred on February 21, 2021 was carried out as verification of flood modeling. The discharge calculation method uses the SCS-CN hydrograph method with a discharge of 1131.5 m3/s with the help of HEC-HMS software. In addition, verification was carried out using Sentinel 1 satellite imagery with the final result in the form of a raster model and Sentinel 2 with the final result in the form of an original image. The use of this satellite imagery can be used as another alternative to verify flood inundation modeling by comparing the size of the flood area from the satellite imagery results and the modeling results. In flood modeling using HEC-RAS software and terrain type in the form of MERIT DEM which is corrected with field measurement data and the original datum elevation which is lowered by 2.5 meters. The purpose of this study is to examine the size of the flood inundation to obtain the level of flood threat with the influence of depth, speed and duration and to determine the amount of losses due to flooding. The level of flood threat in Citarum Hilir is divided into four categories, low, medium, high and very high. The results of this study indicate that flooding inundates agricultural areas, industry, housing, forests, water bodies, main roads and local roads with the areas with the highest area of inundation and high level of flood threat being residential and agricultural areas. In addition, the total loss for all scenarios reaches more than 1 trillion Rupiah. The two areas are areas that influence the sustainability of community life around the Citarum Hilir River because almost the entire area is dominated by agriculture. So there needs to be special attention from the local government to be able to plan the best alternative flood control solutions to reduce the magnitude of flood losses in the affected areas.