Hazard mitigation approach for extreme flooding based on inundation mapping

The Upper Indus Basin (UIB), located in Hindu-Kush Karakoram Himalaya (HKH) region, is predicted to experience increase in precipitation and consequently high inflows according to Representative Concentration Pathways (RCP) 4.5 and 8.5 at global and regional warming thresholds of 1.5 °C and 2.0 °C. Tarbela dam, an outlet for UIB, on the river Indus in Pakistan is one of the biggest earth fill dams in the world having a reservoir capacity of 16.3 billion cubic meters. This study assesses the hazard associated with the Tarbela dam failure through inundation mapping and proposes a comprehensive hazard mitigation plan. The mitigation plan includes details on hazard and risk assessment, early warning and evacuation, and disaster relief efforts. To achieve this, HEC-RAS hydraulic modeling was applied under a hypothetical dam failure scenario triggered by overtopping, providing a high-resolution estimation of inundation extents and depths. In addition, the study uniquely integrates hazard mapping with a risk assessment matrix for emergency response planning, offering a practical framework. The major focus of the investigation is inundation mapping through hydraulic modeling that is performed by HEC-RAS under the hypothetical dam failure caused by overtopping. The findings and recommendations of the study can help the decision makers in developing and implementing a robust emergency action plan for dam-break scenarios and extreme flooding.