Evaluasi kinerja sistem saluran drainase di sekitar kawasan Dusun Krawitan, Kabupaten Sleman, Yogyakarta

The Krawitan Hamlet area, located in Sleman Regency, Special Region of Yogyakarta, has undergone residential development and land-use changes that may affect the performance of the existing drainage system. One of the main problems identified is the absence of drainage channels along several road segments, particularly Kimpulan and  Sakura Road, causing surface runoff to flow over the roadway and resulting in local inundation. This study aims to evaluate the capacity of the existing drainage system, estimate design runoff discharge, redesign channels that are unable to accommodate the design discharge, and plan new drainage channels for road segments that currently lack drainage facilities. The research employed hydrological and hydraulic analyses. Hydrological analysis was conducted using annual maximum rainfall data from 2011 to 2023 obtained from Prumpung Rainfall Station. Design rainfall was determined through frequency analysis using the Log Pearson Type III distribution, which was verified by the Chi-Square goodness-of-fit test. Rainfall intensity was calculated using the Mononobe method, while design discharge was estimated using the Rational Method. Hydraulic analysis was performed to assess channel capacity based on channel geometry and bed slope. The results indicate that, of the six evaluated drainage channels, five existing channels (AB, BC, CE, EG, and FG) are capable of conveying the design discharge. In contrast, there is only one channel has been redesigned, it is DE channel. As additional to improve the drainage system, the two channels (AD and DF) have been planned. Based on the hydraulic design, the redesigned dimensions for channel DE are 0.600 m in width and 0.700 m in depth, including freeboard. Meanwhile, the proposed dimensions for channels AD and DF are 0.600 m × 0.600 m and 0.500 m × 0.500 m, respectively, including freeboard. These improvements are expected to enhance the effectiveness of the drainage system in reducing surface runoff and mitigating inundation within the study area.