THE EFFECT OF NANJUNG TUNNEL, CISANGKUY FLOODWAY AND CIEUNTEUNG DETENTION POND ON THE FLOODS AND INUNDATIONS CONTROLS IN BANDUNG DISTRICT

• Main Author: Phrameswary, Dewi
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/48461
• Institution: Institut Teknologi Bandung

Baleendah subdistrict is a city area in Bandung district which almost every year happens to get flooded. There are several factors causing floods in Baleendah subdistrict; some of them are the massive overload from Citarum river which has small bankful capacity, and the effect of lateral inflow from Cisangkuy river and an extreme condition happening when the floods from both rivers occur at the same moment. Various research infrastructure construction plans have been conducted in Citarum river to overcome and reduce the effects of the floods happening in Baleendah and Dayeuhkolot. Some applied infrastructures construction by the Board of Citarum area (Balai Besar Wilayah Sungai Citarum) are the construction of detention pond of Cieunteung located in Baleendah, the construction of Cisangkuy floodway begun from inlet located in Tarajusari Village of Banjaran subdistrict untill the outlet located in Sangkanhurip Village of Katapang subdistrict, and the construction of Nanjung tunnel on the upstream of Citarum river located in Nanjung. In this study, hydrological analysis was conducted to obtain a design of flood discharge at the research site. Furthermore, a hydraulic analysis was executed to determine the existing conditions of flood for 20 years-returning period to find out how big the impact by using MIKE FLOOD software. Flood modeling was carried out by several scenarios including existing conditions without control attempt, conditions with flood control attempt in Citarum River in the form of the Nanjung Tunnel construction, Cisangkuy Floodway and Cieunteung detention pond, and condition with additional efforts of flood control in Citarum river by a normalization. Those scenarios were analysed to know the impact of floods happening in all locations of the study and the effect of the availability of infrastructure towards floods and inundations in the study area. After reviewed several scenarios and simulated the model by using MIKE FLOOD for 20 years- flood returning period, it was found that scenario 1 with the existing of Citarum River, it obtained that flood water level elevation in Baleendah and around the lower course of Cisangkuy river was +659,58 m with the width of inundations 1,566.6 km². In scenario 2 with the existing of Citarum river and Cisangkuy floodway, the flood water level in Baleendah and around the lower course of Cisangkuy river was +659,31 m with the width of inundation 1480,5 km². The decreasing in flood level elevation occured by 0,27 m and reduction in inundation area by 5%. Furthermore, the result of scenario 3 simulation with the existing of Citarum River, Cisangkuy Floodway and Nanjung Tunnel, it was obtained that flood water level elevation in Baleendah and around the lower course of Cisangkuy river was +659,31 m with the inundation width of 1480,0 km², however, there was no significant decrease in scenario 3. In scenario 4, the existing of Citarum River, Cisangkuy Floodway, Nanjung Tunnel and Cieunteung detention pond were simulated at the same time, the flood water level elevation was obtained around +659,32 m with inundation area around 1476,6 km². The reduction in inundation area was occurred around 6% and the decreasing of flood water level was 0.26 m. In scenario 5, there was an effort to overcome by a normalisation upon Citarum river, the construction of Cisangkuy Floodway and Nanjung Tunnel with the flood water level was being +658,28 m, after that, there was no more inundation at Baleendah. It was also discovered that there was a reduction on the length of inundation in scenario 5 around 6-7 hours compared to the other scenarios which had reduction of inundation time less than 1 hour. From all the scenarios which had been conducted, it was found that the presence of the Cisangkuy Floodway and Najung Tunnel were not significant enough in reducing the flood water level and inundation area in Baleendah. It required a treatment such as normalization in Citarum River to obtain maximum result in reducing the flood effect in Baleendah, it could be seen from scenario 5 where a reduction in the length of inundation time was 6-7 hours if compared to the existing condition of Citarum River without the given treatment.