Flood hazard assessment on the impact of pump operation for flood reduction in The Banger Hilir Subsystem, Pekalongan City, Central Java Province, Indonesia

Abstract The northern part of Pekalongan City is highly vulnerable to flooding, which may originate from river overflow (fluvial), insufficient drainage or extreme rainfall (pluvial), and tidal surges (rob). The city has developed a drainage masterplan that divides the area into eight subsystems. This study focuses on analyzing one of them — the Banger Hilir subsystem. The objective is to compare flood modeling results under two conditions: with and without the operation of pumps. The modeling uses the Personal Computer Storm Water Management Model (PCSWMM) software, applying a combined 1D–2D hydrodynamic approach. Key input parameters include inflow from the surrounding catchment areas, tidal fluctuations at the downstream boundary, and 1D drainage infrastructure such as secondary channels, pump stations, and land use settings. Two simulation scenarios — pump-active and pump-inactive — are analyzed to assess the effectiveness of the Banger Hilir subsystem in managing floodwaters based on flood hazard assessment. The study also evaluates the operational timing and efficiency of the pump system. The findings are expected to provide valuable input for the local government in reviewing and improving the drainage masterplan of Pekalongan City.