Fitri, Dina Risma (2024) Pemetaan Sebaran Banjir Dengan Metode Hec Ras-2d Di Daerah Aliran Sungai Dumai. Other thesis, Universitas Islam Riau.

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Abstract

Flooding is a major issue in Dumai City, caused not only by high rainfall but also by tidal flooding that occurs at specific times each year. The impacts of flooding include inundation of residential areas and commercial establishments, as well as disruptions to road access. Based on these problems, it is crucial to determine the flood discharge and the extent of inundation over the coming years. This study aims to map the distribution of flood inundation and analyze the contributing factors so that the government can prioritize mitigation efforts in areas prone to flooding. The methodology used in this study includes hydrological analysis utilizing local rainfall data from Dumai City between 2009 and 2023. To determine the extent of the flood distribution, the HEC-RAS 2D application was employed, supported by two other applications: HEC-HMS for calculating peak discharge and ArcGIS for creating visual representations of affected areas. Based on the research findings, the peak discharge was 46.4 m³/s for a 10- year return period and 61.6 m³/s for a 25-year return period. Flooding in the Dumai River Basin (DAS Dumai) is caused by a combination of rainfall discharge, tidal effects, and a combination of both. For a 10-year return period, rainfall discharge caused a flood area of 2.6 million m², while tidal effects expanded the area to 13.9 million m². The combination of both factors increased the inundation to 14.2 million m². For a 25-year return period, flooding triggered by rainfall covered an area of 3.2 million m², while tidal effects expanded it to nearly 14 million m². The combination of both factors resulted in the largest impact, with an area of 14.2 million m² and a flood depth of up to 3.291 meters. The primary causes of flooding are flat topography, land-use changes that reduce water absorption, and tidal influences that hinder water flow to the sea, worsening the flooding, particularly in coastal areas such as Laksamana and Rimba Sekampung Subdistricts.

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