A Review of Flood Risk Assessment Due to Probable Maximum Precipitation in the West Rapti River Basin, Nepal

A Review of Flood Risk Assessment Due to Probable Maximum Precipitation in the West Rapti River Basin, Nepal

Ganesh Bhandari

Under the supervision of

Asst. Prof. Himanshu Meena

Department of Civil Engineering, Parul Institute of Engineering & Technology,

Parul University, Gujarat, India

Abstract

Floods driven by extreme precipitation events pose significant risks to communities, infrastructure, and ecosystems, particularly in regions with complex topography, such as Nepal. Probable Maximum Precipitation (PMP) is a critical parameter for assessing flood risk and designing resilient infrastructure. This review examines the methodologies and findings of a study focused on flood risk assessment in the West Rapti River Basin, Nepal, with emphasis on PMP and Probable Maximum Flood (PMF). This study employs hydrometeorological and statistical methods to estimate PMP, utilizes Snyder’s unit hydrograph for PMF calculation, and applies HEC-RAS 2D modeling to map flood hazards, vulnerabilities, and risks. Key findings include PMP estimates of 507 mm and 575 mm, a PMF of 11,211.1 m³/s, and detailed flood risk maps highlighting significant inundation risks in Deukhuri Valley. This review synthesizes the contributions of this study, compares its approaches to global practices, and discusses its implications for flood risk management in Nepal.The study on flood risk assessment in the West Rapti River Basin, Nepal, employs a comprehensive approach to evaluate and map flood hazards, vulnerabilities, and risks. By combining hydrometeorological and statistical methods to estimate Probable Maximum Precipitation (PMP), the research provides crucial insights into extreme precipitation events in the region. The use of Snyder's unit hydrograph for Probable Maximum Flood (PMF) calculation and HEC-RAS 2D modeling for flood hazard mapping demonstrates a robust methodology for assessing flood risks in complex topographical areas.

The findings of this study have significant implications for flood risk management in Nepal and similar regions. The PMP estimates of 507 mm and 575 mm, along with the calculated PMF of 11,211.1 m³/s, provide valuable data for designing resilient infrastructure and implementing effective flood mitigation strategies. The detailed flood risk maps highlighting substantial inundation risks in Deukhuri Valley offer critical information for local authorities, urban planners, and policymakers to develop targeted interventions and improve community preparedness. This research contributes to the broader understanding of flood risk assessment methodologies and their application in regions with challenging topography, potentially informing similar studies in other flood-prone areas worldwide.

Keywords:

Flood risk assessment, West Rapti River Basin, Nepal, Probable Maximum Precipitation (PMP), Snyder's unit hydrograph, Probable Maximum Flood (PMF), HEC-RAS 2D modeling, Flood hazard mapping, Deukhuri Valley, Flood mitigation strategies, Hydrometeorological methods, Statistical analysis, Extreme precipitation events, Flood risk management, Inundation risks