Analisis Pemetaan Daerah Genangan Banjir di Daerah Aliran Sungai Mencirim Menggunakan Sistem Informasi Geografis (SIG)

Abstract

Flooding in the city of Binjai is a frequent issue during the rainy season, and its affected area continues to expand. Flood disaster management must begin with the provision of information regarding flood-prone areas. One of the rivers that often experiences flooding in Binjai is the Mencirim River, which is a tributary of the Mencirim Watershed (DAS Mencirim) that runs through the city for approximately 11.9 km. The aim of this study is to provide information to the public as part of disaster mitigation efforts by analyzing annual maximum rainfall data to estimate design flood discharges for return periods ranging from 2 to 100 years, using HEC-RAS software. Additionally, flood inundation maps are generated using QGIS software. The study concludes that the design flood discharges modeled using HEC-RAS are: 208.291 m³/s for a 2-year return period (Q2), 252.414 m³/s for Q5, 281.627 m³/s for Q10, 318.538 m³/s for Q25, 345.920 m³/s for Q50, and 373.100 m³/s for Q100. These discharges exceed the river’s capacity and pose a flood threat that could result in floodwater heights reaching 1 to 2,5 meters above the Mencirim River’s normal water level.