Analisa Area Genangan Banjir Sungai Babura Berbasis HEC - RAS dan GIS

Abstract

Floods are natural disasters that often occur in Indonesia, especially the city of Medan. Maps of areas prone to natural disasters, especially flood inundation, are needed for flood disaster mitigation. This study aims to produce a map of the Babura River flood inundation that crosses the Medan City area due to the overflow of the Babura River. Field cross section measurement data, Light Detection and Ranging (LiDAR) topography, Digital Elevation Model (DEMNAS) topography were used to determine elevation differences using Global Mapper software, and flood inundation map modeling integrating the Hydrologic Engineering Center- River Analysis System (HECRAS) software with QGIS software. The Log Person III method fulfills the requirements for distribution of rainfall frequency distribution, the chi-square test, and the Smirnov-Olmogorof test. The Nakayasu Synthetic Unit Hydrograph method was used to calculate the discharge at 1, 2, 5, 10, 20, 25, 50, and 100 years. From the results of flood inundation analysis using LiDAR topographic data, it is known that 19 urban villages in Medan City have the potential to be flooded, namely Anggrung, Beringin, Darat, Gedung Johor, Jati, Kesawan, Kwala Bekala, Mangga, Merdeka, Padang Bulan, Pangkalan Mansyur, Pasar Merah Barat, Petisah Hulu, Petisah Tengah, Polonia, Sarirejo, Sikambing D, Simalingkar B, dan Titi Rantai.. The value of RMSE (Root Mean Square Error) cross section field to topographic LiDAR data, topographical data DEMNAS, and cross section data LiDAR topography to DEMNAS topographic data is 2.73; 4.74; 3.40; and the RMSE value of the inundation area of the LiDAR topographic data to the topographical data of DEMNAS of 0,1052; 0,1176; 0,1208; 0,1250; 0,1252; 0,1253; 0,1253; 0,1210; for 1, 2, 5, 10, 20, 25, 50, and 100 year return discharges.

Banjir merupakan kejadian bencana alam yang sering terjadi di Indonesia khususnya Kota Medan. Peta kawasan rentan bencana alam khususnya genangan banjir diperlukan untuk mitigasi bencana banjir. Penelitian ini bertujuan untuk menghasilkan peta genangan banjir Sungai Babura yang melintasi kawasan Kota Medan akibat meluapnya Sungai Babura. Data pengukuran cross section lapangan, topografi Light Detection and Ranging (LiDAR), topografi Digital Elevation Model (DEMNAS) digunakan untuk mengetahui perbedaan elevasi menggunakan software Global Mapper, dan pemodelan peta genangan banjir mengintegrasikan software Hydrologic Engineering Centre-River Analysis System (HECRAS) dengan software QGIS. Metode Log Person III memenuhi syarat agihan distribusi frekuensi curah hujan, uji chi-kuadrat, dan uji smirnov-olmogorof. Metode Hidrograf Satuan Sintetik Nakayasu digunakan untuk menghitung debit kala ulang 1, 2, 5, 10, 20, 25, 50, dan 100 tahun. Dari hasil analisis genangan banjir menggunakan data topografi LiDAR diketahui bahwa 19 kelurahan yaitu Anggrung, Beringin, Darat, Gedung Johor, Jati, Kesawan, Kwala Bekala, Mangga, Merdeka, Padang Bulan, Pangkalan Mansyur, Pasar Merah Barat, Petisah Hulu, Petisah Tengah, Polonia, Sarirejo, Sikambing D, Simalingkar B, dan Titi Rantai. Nilai RMSE (Root Mean Square Error) cross section lapangan terhadap data topografi LiDAR, data topografi DEMNAS, dan cross section data topografi LiDAR terhadap data topografi DEMNAS adalah 2,73; 4,74; 3,40; serta nilai RMSE area genangan data topografi LiDAR terhadap data topografi DEMNAS sebesar 0,1052; 0,1176; 0,1208; 0,1250; 0,1252; 0,1253; 0,1253; 0,1210; untuk debit kala ulang 1, 2, 5, 10, 20, 25, 50, dan 100 tahun.