Evaluasi Kapasitas dan Efektifitas Saluran Drainase (Studi Kasus : Jln.Bengkalis – Gg. Kebun Kapas II – Gg. Cikmas Ayu Kel. Rimbas Sekampung Kec. Bengkalis).

Drainage is one of the important infrastructures in residential areas that functions to convey rainfall runoff and prevent water accumulation and flooding. This study aims to determine the existing condition of the drainage network, calculate rainfall runoff discharge, evaluate the capacity of existing drainage channels to accommodate runoff, and identify the direction of drainage flow toward the main channel or outlet in Rimbas Sekampung Village, Bengkalis District. Field surveys were conducted to obtain channel dimension, elevation, and physical condition data. Hydrological analysis was carried out using the Rational Method, while channel capacity was evaluated using the Manning Equation. Drainage network mapping and flow direction identification were supported by ArcGIS. The results show that the drainage system consists of primary and secondary channels that generally remain functional. However, several sections were found to have sedimentation, waste, vegetation, inadequate channel slopes, and the absence of permanent drainage channels. The design runoff discharges for return periods of 2, 5, 10, 25, and 50 years were 4.46, 6.07, 7.13, 8.35, and 9.46 m³/s, respectively. The capacity of the primary channels was 1.502326725 m³/s, while the secondary channels had a capacity of 10.40198719 m³/s, resulting in a total drainage capacity of 11.90431391 m³/s. The comparison indicates that the total drainage capacity is greater than the design runoff discharge for all analyzed return periods. The overall flow direction leads toward the main channel and outlet, although several sections experience backwater due to elevation conditions, while Gang A1 and Gang C2 do not yet have permanent drainage channels. Therefore, routine maintenance, channel slope improvement, and construction of drainage channels in sections without permanent facilities are required to improve the effectiveness of the drainage system. The results are expected to provide a basis for determining priorities for drainage system improvement and maintenance.