The assessment of flood hazard in Pondok Keumuning village of Langsa City, Aceh due to heavy rain in 2020

Abstract

Langsa faces the recurring threat of floods every year, primarily caused by high rainfall resulting in surface runoff in the Langsa Watershed. However, there is uncertainty regarding the specific causes of flooding in the city. This research discusses the flood hazards generated by Langsa River due to high rainfall in Keumuning Village, Langsa City, in 2020. The data utilized in this study includes daily rainfall data obtained from PTPN I Langsa, specifically from the Kebun Lama (KLM), Kebun Baru (KBR), and Tualang Sawit (TWS) stations. Additionally, observed water level data is collected from the Keumuning water gauge station operated by the Aceh Irrigation Agency. Since there is no river discharge record at the Keumuning water gauge station, the Nreca method is used to analyze the direct runoff from the Langsa Watershed due to rainfall, linking it to the water level at Keumuning. Historical flood event data is compiled from the Regional Disaster Management Agency of Langsa City, online media sources, and interviews with flood-affected communities. The research findings indicate that floods in Keumuning Village, Langsa, are triggered by high rainfall, leading to increased river discharge as a result of heavy rainfall at the TWS station (located upstream in the Langsa Watershed) with a 2-year return period. This can result in flooding for the villages around the Langsa River. Similarly, suppose rainfall reaches a 2-year return period at the KLM and KBR stations situated within the middle and downstream of the Langsa Watershed. In that case, it poses a flood threat to the upstream villages along the estuary branches. However, further studies are necessary to assess compound floods triggered by tidal water levels, rainfall, and river discharge in the vicinity of these estuary branches.