Impact evaluation of Cilember River normalisation to PURBALEUNYI Toll Road using two dimensional model HEC-RAS

Abstract

Cilember River flows from North to South of Cimahi and crosses PURBALEUNYI Toll Road in downstream. Therefore normalization of Cilember River Cimahi can impact the PURBALEUNYI Toll road. Hydraulic simulation carried out to determine the impact and formulate the mitigations alternatives. The study was conducted based on Detail Engineering Design Data for Cilember Normalisation Program prepared by Citarum River Authority as a base data. Two-dimensional HEC-RAS model was used to simulate the impact of the river normalization program. The model also used to evaluate the alternatives (detention pond, diversion of flows) to minimize the impact of the Cilember normalization program to PURBALEUNYI Toll road. Applying 10 year return period and HEC-RAS simulation, with an existing condition, 26 505 sqm area is inundated mostly in the North area of Toll Roads. After the normalization program, the inundation area shifts to the south area, including Toll road. The further simulation shows that normalization of the river can reduce inundation area to 7 993 sqm. Simulation of combination between detention pond and diverting the excess flow of Cilember to Kali Malang inundated area occurs, but it does not affect the toll road.