The 2018 Kerala flood caused widespread devastation, leaving a lasting impact on agricultural activity in Alappuzha district, which is characterized by its low-lying terrain, extensive water bodies and its vulnerability to extreme weather events exacerbated by climate change. By integrating hydrological and geospatial methods, this research aims to offer a thorough knowledge of the losses associated with the flood’s impact on agriculture. A 30-m resolution Digital Elevation Model (DEM) and HEC-RAS hydrodynamic modeling were used to create a flood inundation map that indicated the areas that were submerged during the flood, while a Land Use Land Cover (LULC) map was made to identify agricultural areas throughout the district. By overlaying these maps on LULC map, the extent of the flooded agricultural land was determined. The findings indicate the extent of agricultural damage, highlighting the most vulnerable areas,16% of the total area of the district is covered with agricultural land and in that 97.82% of the agricultural land was affected by the flood. It was determined that both flood depth and flood duration significantly affect the level of agricultural damage the maximum depth of inundation in the agricultural was 13.7 m and the longest duration of inundation is 13 days, with prolonged inundation resulting in greater economic losses. Given the rising frequency and severity of floods linked to climate change, this study emphasizes the urgent need for efficient flood risk management techniques.