Terrain based prioritization of urban waterbody restoration using topography drainage connectivity and groundwater conditions in Delhi

Abstract Urban waterbodies in Delhi have been severely impacted by rapid urbanization, encroachment, and the modification of natural drainage pathways, making restoration prioritization challenging at a city scale. This study evaluates the restoration potential of urban waterbodies in the National Capital Territory (NCT) of Delhi by integrating satellite imagery, terrain characteristics, drainage conditions, and groundwater data. Sentinel-2 imagery, Cartosat Digital Surface Model (DSM) data, groundwater monitoring records, climatic data, and official water body inventories were combined within a GIS-based framework. A total of 1,167 waterbodies were identified, including unrecorded sites missing from official records. Ground verification demonstrated high spatial accuracy, achieving 92% overall accuracy and a Kappa coefficient of 0.88. A novel Terrain Connectivity Index (TCI) incorporating elevation differences, upstream catchment contributions, and topographic barrier conditions was developed to quantify relative terrain-supported restoration suitability. TCI values across all identified sites ranged from 0.15 to 0.87. Based on terrain and drainage parameters, 212 waterbodies (18%) exhibited favorable conditions for terrain-supported restoration, whereas 955 sites (82%) were classified as hydrologically constrained. District-level analysis revealed a higher proportion of viable restoration sites in East Delhi, Southeast Delhi, and Shahdara, whereas South Delhi and New Delhi were largely constrained by elevated topography, fragmented drainage, and deeper groundwater tables. These findings highlight that integrating terrain, drainage, and hydrogeological parameters provides a robust spatial framework for prioritizing urban water body restoration in Delhi.