EVALUASI KAPASITAS SALURAN DRAINASE UNTUK MENCEGAH TERJADINYA BANJIR DI KAWASAN PERUMAHAN PONDOK PERMATA SUCI KECAMATAN MANYAR KABUPATEN GRESIK

Abstract

Land-use conversion from natural catchment areas into densely populated residential zones in Gresik Regency has significantly triggered an increase in surface runoff. This phenomenon induces seasonal flooding issues in the Pondok Permata Suci Housing estate, Manyar District. This study aims to evaluate the hydraulic capacity of the existing drainage channels, project domestic wastewater and design flood discharge, redesign the channel cross-sectional dimensions, calculate the required volume of the long storage, and formulate comprehensive Operation and Maintenance (O&M) guidelines. The hydrological analysis in this study applies the Gumbel Distribution method to estimate the design rainfall across various return periods, alongside the Rational Method to calculate the design flood discharge based on the characteristics of the catchment area. The capacity evaluation indicates that the current dimensions of the existing drainage channels are inadequate to optimally accommodate the accumulated discharge of stormwater runoff and household wastewater. As a technical solution to mitigate this capacity reduction, a structural engineering redesign of the channel cross-sections was conducted, utilizing a minimum dimensional adjustment interval of 0.1 m up to a maximum of 0.4 m. Furthermore, a long storage unit was designed in section C, measuring 210 m x 3.5 m with a depth of 1.5 m, equipped with a pump unit with a capacity of 0.576 m³/s to provide temporary water retention when the river water level outside the area overflows. To ensure the sustainability and long-term effectiveness of the planned drainage system, an integrated maintenance strategy was formulated, encompassing community-based routine maintenance, periodic maintenance, special maintenance, and structural rehabilitation to minimize sedimentation risks and extend the service life of the infrastructure.