Optimization of the Retarding Basin Maximum Capacity to Reduce Flood Peak Discharge

Abstract

This research intends to analyze optimal storage capacity of retarding basin (V_k optimal) in reducing the flood peak discharge (DQ_p) in the downstream control point. The methodology consists of simulation in several placing of retarding basins (R_AK) and various maximum storage capacity (V_k) for various flood return periods (Q_T). This research is conducted in agglomeration urban area of Wonosari, Gunungkidul Regency, Daerah Istimewa Yogyakarta-Indonesia. There are planned 5 retarding basins that are Purbosari, Jeruk, Kepek, Purwosari, and Trimulyo. The optimal result of maximum storage capacity (V_k) due to the reduction of flood peak discharge (DQ_p) for the retarding basin of Purbosari (R_Ak = 7.01%) produces the optimal storage capacity (V_k optimal) about 886.45 x 10³ m³ and it can reduce the flood peak discharge (DQ_p) about 6.20%; however, for the retarding basin of Jeruk (R_Ak = 8.65%) produces the optimal storage capacity (V_k optimal) about 1000.01 x 10³ m³ and it can reduce the flood peak discharge (DQ_p) about 7.56%; for the retarding basin of Kepek (R_Ak = 21.34%) produces the optimal storage capacity (V_k optimal) about 1069.88. x 10³ m³ and it can reduce the flood peak discharge (DQ_p) about 14.23%; for the retarding basin of Purwosari (R_Ak = 60.11%) produces the optimal storage capacity (V_k optimal) about 1266.92. x 10³ m³ and it can reduce the flood peak discharge (DQ_p) about 26.45%; and for the retarding basin of Trimulyo (R_Ak = 66.52%) produces the optimal storage capacity (V_k optimal) about 1266.94. x 10³ m³ and it can reduce the flood peak discharge (DQ_p) about 29.27%.