STUDY EFFECTIVENESS OF DETENTION POND FOR FLOOD REDUCTION AND EFFORTS TO PROVIDE RAW WATER NEEDS IN SOUTH OF BANDUNG AREA

• Main Author: Khalifah Ibrahim, Fadel
• Format: Theses
• Language: Indonesia
• Subjects: Teknik sipil
• Online Access: https://digilib.itb.ac.id/gdl/view/36507
• Institution: Institut Teknologi Bandung

Almost every year, floods inundate the South Bandung Region, especially in Baleendah District, Bojongsoang, and Dayeuh Kolot. The flood was caused by several factors, including high rainfall; accumulated flow discharge from the Upper Citarum, Citarik, Cikeruh, Cipamokolan, Cidurian, Cicadas, Cikapundung, and Cisangkuy Sub-basins; limited capacity of the Citarum River; and the conditions of land use in some of the Citarum sub-watersheds are quite bad. The purpose of this study is to obtain the concept of flood control and management that can be used in the South Bandung area, especially in Baleendah District, Bojongsoang, and Dayeuh Kolot. The efforts made are through a combination of water storage with a side spill way system and efforts to normalize the Citarum River from the government. From the volume of water storage that has been obtained, it is expected to be able to reduce the flood discharge that occurs at a time of 20 years and 50 years and can be an additional water supply for sources of fulfillment of raw water needs that are felt to be lacking in Bandung Regency and Bandung City. Rainfall analysis uses maximum rainfall data for each sub-watershed obtained from several rain stations scattered in almost all sub-watersheds that are being studied. The data used are daily rainfall data from 2004-2017, analyzed using the polygon thiessen method and for consistency tests using the RAPS method. For the hourly rain distribution model, use the ABM model. Flood hydrograph analysis using the Nakayasu, SCS, original ITB, ITB 1, exact and numerical ITB synthetic hydrograph approach, and Snyder-Alaexeyev The calibration process uses AWLR observation data in the field (AWLR Cikapundung Ps.Luyu, AWLR Cisangkuy Kamasan, and Citarum AWLR Dayeuhkolot as calibration, as well as calibration area. Flood search is completed through hydrological equations and hydraulic equations. Hydrological search uses HECHMS devices for synthetic hydrograph approach for sub-watersheds that do not have AWLR data in the field for modeling inundation using the results of previous synthetic hydrographs. Flood hydrograph analysis using the Nakayasu synthetic hydrograph, SCS, original ITB, ITB 1 (exact, numerical) and ITB 2 (exact, numerical), and Snyder-Alaexeyev approaches. As a calibration process, a flood event was used on March 13, 2014 for daily debit calibration using AWLR observation data in AWLR Cikapundung Ps.Luyu, AWLR Cisangkuy Kamasan, and AWLR Citarum Dayeuhkolot. Flood search is solved through hydrological equations and hydraulic equations. Hydrological search uses the HEC-HMS device and the synthetic hydrograph above. Whereas hydraulic tracking is used for flood inundation modeling using the results of previously selected synthetic hydrographs. Flood inundation modeling uses the existing cross section data of the Citarum River as an initial stage to determine the existing river capacity and inundation models that occur, and the Citarum River normalization data combined with detention ponds, side spill ways, and planned flood diversion channels as a flood control model. The flood inundation is modeled in the form of 1D/ 2D using DEMNAS data. The raw water requirements refer to the 2016 Citarum River Basin Water Resources Management Plan data which shows the minimum discharge during the dry season (June - September). In the dry season, the water supply deficit for raw water is planned to be supplied by the detention pool. Based on the results of the study, it was found that flood control by using detention ponds and flood transfer channels can effectively be applied. These efforts are in accordance with the direction of the development of the RPJMD of West Java Province for 2013-2018. But with the detention pool, the allotment of space in the 2016-2036 Regency Bandung spatial pattern plan will change. The changes include wetland agriculture (81.49 ha), residential area (58.67 ha), industrial designation area (2.94 ha), and a small portion of the river border (1.68 ha). As a result, changes in the pattern of space will have positive and negative effects. The effectiveness of flood control and mitigation in the South Bandung Region, especially in Baleendah District, Bojongsoang, Dayeuhkolot and related efforts to meet raw water needs in Bandung Regency and Bandung City, can be seen as follows: 1) There was a decrease in flood inundation from the simulation results before handling ( existing river cross section) and after control (normalized cross section plus detention pool and floodwater evacuation control channel due to the implementation of flood control scenario as follows: a) Q20 from depth 2.84 m to 1.74 m, b) Q50 from depth 3.21 m to 1.69 m . With the remaining flood inundation, dikes are planned in several river segments, such as in the Dayeuhkolot area with a height of 2.45 m; 2) Effectiveness of flood control on inundation area based on the 1D / 2D model related to conditions before handling and after handling is very effective where the percentage decrease in flood inundation area in Q20 is 98.77% and Q50 89.08%; 3) Effectiveness of flood control on inundation volume based on 1D / 2D model related to conditions before handling and after handling is quite effective with the percentage decrease in flood inundation area in Q20 of 46.73% and Q50 of 47.54%; 4) Number of inhabitants (souls) who are able to be served by the addition of detention ponds and existing capacity of PDAMs to serve raw water needs in Bandung Regency and Bandung Regency in 2037 for 120 days (June - September) as many as 575 peoples. The amount is obtained based on consumption of water table for the city with a population of> 1,000,000 as much as 190 liters / person / day.