Evaluation of The Drainage System at The University of Pahlawan Tuanku Tambusai Based on An Analysis of The Rainfall Catchment Area

Abstract

Infrastructure development at the Universitas Pahlawan campus has led to land-use changes that potentially increase surface runoff and affect the performance of the drainage network. This study aims to analyze catchment area characteristics, calculate design runoff discharge, and evaluate the capacity of the existing drainage network by comparing design runoff discharge with channel capacity. A quantitative descriptive method was employed, utilizing hydrological and hydraulic analysis approaches. Data sources included 10 years of rainfall data from the Silam Station, topographic data and field observations, Rainfall analysis was conducted using probability distributions; runoff discharge was calculated using the Rational Method, and channel capacity was analyzed using Manning's Equation. The results indicate that the Universitas Pahlawan campus area is divided into four catchment zones (A1, A2, A3, and A4) with a total area of 4,27 hectares. Frequency analysis identified the Log Pearson III distribution as the best fit, yielding a design rainfall of 150.31 mm for a 10 year return period. Of the 12 channels evaluated, all channels were individually capable of accommodating the design runoff discharge; however, overtopping was identified in Channel 10, as this channel is located at the confluence of four flows from Zones A1 to A4 that converge at the same outlet point, causing the discharge from the four upstream channels to concentrate simultaneously and exceed the channel's holding capacity. This study provides information on the performance of the campus drainage system and serves as a basis for considering capacity improvements and regular channel maintenance.