Improving resilience to water-induced disasters is a key for achieving water security. However, many studies related to water security assessment tend to focus more on water quantity and quality and less on disaster resilience aspect. This study aimed at flood hazard mapping and vulnerability assessment of agricultural land, agriculture production losses, and infrastructure losses/damages to provide useful information for the assessment of water security. Flood hazard maps were developed for 2, 10, 25, 50 and 100 years return period of West Rapti Watershed (WRW) in Dang district of Nepal and probabilistic assessment of agricultural vulnerability and loss. Two-dimensional hydrodynamic model ware developed in HECRAS 6.1.0 for the flood hazard mapping with the various return periods. The 100 years return period flood discharge of 5816 m3/s has resulted the maximum inundation depths of 13.6m. This inundated 5849.26 Ha total area, including 3965 Ha agricultural land and 3137 number of various types of building (adobe, wooding, brick masonry, and RCC). Similarly, larger paddy field areas are affected by flooding during the vegetative stage rather than reproductive and maturity stages. Such results are useful to enrich the current extent of hazard and impacts, potential ways for reducing the hazard and vulnerability, and ultimately contribute to water security planning for an area of interest.