Evaluation of Drainage System on the Samarinda – Bontang Axis Road, East Kalimantan

The Samarinda–Bontang axis road is the main route connecting cities in East Kalimantan to APT. Pranoto International Airport and connecting to Bontang and Tanjung Santan oil refineries. At STA 0+000 (Muara Badak three way juction) to STA 4+250 it often experiences flooding which can hamper transportation activities. The cause of flooding is from changes in land use and the existing condition of the channel that is too small. The purpose of this study was to evaluate the capacity of the drainage channel on the Samarinda-Bontang axis road. Calculation of flood discharge of 5- year return period using the Nakayasu SUH method and flow modelling using the HEC-RAS application program. The 5-year design flood discharge for each channel is obtained as follows: the Right 1 was 2.323 m³/s, the Right 2 was 4.211 m³/s, the Right 3 was 12.469 m³/s, the Left 1 was 11.163 m³/s, the Left 2 was 14.759 m³/s and the Left 3 was 22.934 m³/s. It was concluded that Right Channel 1 did not overflow while the drainage channels, Right 2, Right 3, Left 2, and Left 3 overflowed. Because the dimensions of the new design channel are much larger, it is necessary to design other flood management alternatives such as the creation of reservoirs and/or infiltration wells