Dam Breach Analysis Using HEC-RAS 2D Flow Method for Yanda Dam
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Date
2023-03
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Addis Ababa University
Abstract
The construction of dams offers numerous advantages to society, but the failure of dams has led to some of the most devastating flood disasters. Given that many dams are being built in Ethiopia so it is important to assess the potential for dam failure to prevent harm to downstream areas. Yanda Dam is also one them which currently under construction for irrigation purposes. This study analysis uses HEC-RAS 2D model to simulate breach events at Dam and examine the resulting consequences downstream.
After analyzing the hydrology of the study area HEC-HMS was used to produce PMF hydrographs based on PMP values and hourly hyetographs, which were critical for simulating dam breach scenarios within HEC-RAS. The generated hydrographs allowed for the representation of extreme hydrologic conditions and simulation of the breach dynamics and the subsequent downstream flooding. This is also critical for simulating the worst-case flood scenario associated with a dam breach.
The breach parameter (the Breach Width, Breach Side Slopes, and Breach Formation Time) is determined based on Dam and Reservoir Characteristics. Then the model is run using 2D unsteady flow method to route the inflow hydrograph, the result output shows failure of the dam causes significant amount of human life loss and economic loss. HEC-RAS 2D model predict at the dam failure the breach outflow Q = 14441.92m3/s, V = 7.9m/s and depth of flood 35.19m.
The study produces an Inundation Map that shows potential flooding areas to enhance decision-making processes and early warning systems with a comprehensive emergency action plan to enhance preparedness, improve response coordination, and ultimately save lives while minimizing economic losses during flood events.
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Keywords
Dam Breach, HEC-RAS, PMP, PMF, HEC-HMS, Rainfall-Runoff