Flood mitigation of Bila River in Sidrap Regency Indonesia based on eco-drainage retention pond

This study aims to analyze the distribution of floods in the Bila River and its countermeasures in reducing the impact that occurred in Sidrap Regency. The study performs hydrological analysis using the Bila watershed rainfall data, calculates the planned flood discharge using the HSS SCS model, and simulates the flood flow profile using the HEC-RAS 2D numerical model. It is found that the Q20 flood discharge of the Bila and the Bulucenrana Rivers entered the Bila River downstream calculated from the HSS SCS analysis are 738.60 and 779.50 m3/s, respectively. The overflow of the Bila River flood affects 9 villages, namely Kalola Village (0.06 km2), Sogi Village (0.01 km2), Kalosi Alau Village (0.32 km2), Kampale Village (0.11 km2), Salomalori Village (0.42 km2), Tanru Tedong Village (2.12 km2), Kalosi Village (0.91 km2), Salobukkang Village (1.70 km2), and Taccimpo Village (4.01 km2). It is proposed that the best solution to deal with the issue is by introducing an eco-drainage system, namely by constructing a retention pond with a maximum storage volume of 3.81 million m3 or with a normal storage of 2.4 million m3. The existence of a retention pond can reduce the inundated area around 8.28 km2 or 85.71%.