Floods are among the most destructive natural disasters, significantly impacting human lives, especially in India’s coastal regions. This study aims to develop a flood susceptibility zone map for the Kollidam Lower Watershed in Cuddalore District, Tamil Nadu, utilizing geospatial techniques and the Frequency Ratio (FR) model. The flood susceptibility map was developed using twelve influential conditioning parameters: Land use/Land cover (LULC), slope, elevation, drainage density, lithology, soil type, Topographic Wetness Index (TWI), proximity to streams, average rainfall, Topographic Rugged index (TRI), Normalized Difference Vegetative Index (NDVI), and surface runoff. A total of 163 historical flood location points were considered, with 133 used to construct the FR model for generating flood susceptibility maps and the remaining 30 points reserved for validation. All variables were resampled to a 30 × 30 m pixel resolution and categorized using the quantile approach. The FR probability model evaluated the correlation between each class and flood frequency. The reclassified frequency ratio model categorized flood susceptibility into five classes: low, moderate, high, and very high susceptibility. The analysis revealed that areas with moderate, high, and very high flood susceptibility covered 20.61, 6.29, and 7.15 square kilometers, respectively. The model demonstrated a success rate of 86% and a prediction accuracy of 77%, confirming that the FR model is a robust, straightforward, and reliable tool. It can effectively aid residents and government officials in devising strategies to mitigate the impact of devastating flood disasters.
