Evaluasi Debit Banjir Pada Sistem Saluran Drainase Di Kawasan Simpang Joglo, Surakarta

Faqih Faisal Arian, Agung Wahyudi Biantoro

Abstract

The Simpang Joglo area in Surakarta is one of the strategic zones with high traffic activity that frequently experiences ponding during heavy rainfall. This condition indicates that the existing drainage system has not been functioning optimally in accommodating the flood discharge that occurs. This study aims to evaluate the design flood discharge and the capacity of the existing drainage channels in the Simpang Joglo area, Surakarta. The method used is a descriptive evaluative analysis with hydrological and hydraulic approaches. Maximum daily rainfall data over a 10-year period were analyzed using several probability distribution methods to obtain the design rainfall, after which the flood discharge was calculated using the Rational Method. The evaluation of channel capacity was carried out through hydraulic calculations and modeling using EPA SWMM 5.2 software.

The results show that for Channel A, the channel discharge of 0.16 m³/s is smaller than the design discharge of 1.44 m³/s; for Channel B, the channel discharge of 0.10 m³/s is smaller than the design discharge of 1.75 m³/s; for Channel C, the channel discharge of 0.27 m³/s is smaller than the design discharge of 1.32 m³/s; while for Channel D, the channel discharge of 0.85 m³/s is greater than the design discharge of 0.60 m³/s. Therefore, it can be concluded that Channels A, B, and C do not meet the required capacity, whereas Channel D meets the capacity requirement.The channel capacity was further analyzed using EPA SWMM 5.2 to obtain more accurate results. The model design consisted of 12 subcatchments, 15 junctions, 1 outfall, and 13 conduits. The simulation results indicate that Channels A, B, and C experience overflow, while Channel D does not. Thus, both the flood discharge calculations and the analysis using EPA SWMM 5.2 produced consistent and corresponding results. Based on these findings, the proposed alternative solution is the construction of 50 infiltration wells. The analysis and calculations show that the implementation of infiltration wells in the Simpang Joglo area, Surakarta, is capable of reducing stormwater runoff that cannot be accommodated by Channels A, B, and C, thereby mitigating flood inundation in the area.