Unveiling the nexus of paddy fields and flooded environments: a probabilistic approach to flood impact assessment and loss estimation in paddy agriculture

Nepal ranks among the most vulnerable countries globally to flood hazards, especially in the southern plains, where the West Rapti River (WRR) is situated. This study presents a systematic approach to developing a flood hazard map and quantifying agricultural vulnerability and losses in paddy and maize using the HEC-RAS 2D model and GIS in the flood-prone area of WRR (from Lalmatiya to Satbariya). Utilizing hydrological data from 1976 to 2015, flood hazard maps were generated for various return periods to estimate probable flooding impacts. The flood hazard assessment results were then used to analyse crop vulnerability and losses, classifying agricultural land into six zones of loss severity, ranging from minor (0–300 dollars per hectare) to major (1500–1800 dollars per hectare). The depth of inundation and duration of water logging are critical factors in determining crop vulnerability and economic impact. In paddy fields, losses escalate exponentially with greater inundation depths, while in maize fields, the increase follows a more linear trajectory. These findings enhance understanding of flood hazard areas, crop vulnerability, and losses, providing critical insights for flood management and agricultural resilience in flood-prone regions.