Governance as the determinant of NbS feasibility: A spatial diagnostic framework for urban watersheds in Kolkata

Urban watersheds in rapidly expanding deltaic regions face accelerating ecological decline that is often attributed to land-use change and hydrological stress. However, the institutional arrangements that govern these systems remain insufficiently examined. This study assesses the Bagjola Canal watershed in Kolkata to demonstrate how governance fragmentation determines the feasibility of nature-based solutions (NbS). A mixed-methods framework integrates Regional Condition Assessment (RCA), land-use and water-quality analysis, groundwater trends, and stakeholder interviews to evaluate ecological condition, infrastructural performance, and institutional coherence across the watershed. Results show pronounced variation in NbS feasibility tied to governance configuration. Conservation and passive recreation zones retain comparatively strong ecological baselines, yet persistent coordination gaps between Kolkata Municipal Corporation (KMC) and the Irrigation & Waterways Department (IRWWD) limit restoration potential. Residential and industrial zones record the lowest RCA scores due to severe encroachment, poor water quality, and weak maintenance regimes. Groundwater over-extraction emerges as a governance-driven response to contaminated surface water, creating a reinforcing cycle of subsidence and canal degradation. A spatial prioritisation identifies three intervention zones: an Upper Zone where NbS is currently unviable due to fragmented authority and tenure conflict; a Middle Zone suitable for hybrid community–state interventions; and a Lower Zone with the strongest ecological and institutional conditions for conventional NbS. The study advances a governance-sequenced approach to NbS planning, demonstrating that institutional readiness is a prerequisite for environmental restoration in hybrid urban territories. The framework offers a diagnostic tool for designing phased, context-appropriate interventions in rapidly urbanising regions.