PLANNING BLUE-GREEN INFRASTRUCTURE FOR CARBON SINK ENHANCEMENT AND POLLUTION MITIGATION: A CASE STUDY OF PATNA, BIHAR

Abstract

Patna, the rapidly urbanizing capital of Bihar situated along the Ganga riverfront, faces severe environmental degradation characterized by extreme air pollution (PM₂.₅ levels averaging 118 µg/m³), critically low green cover (8.3% against WHO standards), pronounced urban heat island effects (+2.8°C), floodplain degradation, and recurrent flooding. These challenges, exacerbated by uncontrolled urban sprawl, population growth from 1.68 million (2011) to projected 6 million by 2031, and fragmented environmental governance, threaten sustainable urban development and public health. This study develops a comprehensive Blue-Green Infrastructure (BGI) framework for Patna to enhance carbon sequestration capacity, mitigate air and water pollution, and build climate resilience through nature-based solutions. The objectives encompass baseline environmental assessment through GIS analysis, quantification of current carbon sink capacity (4,086 Tons CO₂/year), formulation of strategic BGI interventions targeting 475% sequestration enhancement (23,520 Tons CO₂/year), air pollution reduction (18-24% PM₂.₅ decrease), and creation of integrated green-blue networks across 47 km corridors, 2,340 hectares urban forests, and 1,250 hectares restored wetlands. The methodology integrates primary data collection (850 household surveys, 45 expert interviews conducted 2-6 March 2026) with secondary sources including Census 2011, Patna Master Plan 2031, Sentinel-2 satellite imagery, CPCB pollution records, and IMD climate data. Advanced GIS techniques (NDVI analysis, spatial autocorrelation, vulnerability indexing), IPCC-based carbon sequestration modelling, and statistical validation establish baseline conditions and intervention potentials. Key findings reveal acute green space deficits (1.8 m²/person vs. 10.5 m² WHO norm), pollution hotspots in 62% of wards, and floodplain connectivity loss affecting 35% of the city area. The proposed BGI Master Plan introduces a five-layer spatial strategy—green corridors, urban forests, wetlands revival, blue networks, and distributed green infrastructure - phased across short-term (2026-28: priority corridors), medium-term (2029-31: forest expansion), and long-term (2032-40: city-wide integration) horizons with INR 2,840 crores financing from municipal (20%), state/national (30%), private (25%), community (15%), and international sources (10%). Aligned with AMRUT 2.0, Smart Cities Mission, National Mission for Clean Ganga, and UN SDGs 3, 6, 11, 13, 15, the framework demonstrates a benefit-cost ratio of 3.18:1, 4.8-year payback, and 11.2% IRR through enhanced ecosystem services, flood risk reduction (35-40%), UHI mitigation (1.8-2.2°C), and equitable green access (12.5 m²/person by 2031). Zonal proposals prioritize vulnerable low-income wards while integrating governance through the proposed Patna Blue-Green Infrastructure Authority (PBGIA). This data-driven, contextually adapted BGI strategy addresses Patna's unique constraints - resource limitations, institutional fragmentation, land scarcity - while leveraging global best practices from Singapore's ABC Waters, Copenhagen's cloudburst management, and Indore's urban forestry. The comprehensive plan establishes Patna as a model for climate-resilient urban planning in India's Gangetic plains, demonstrating that integrated blue-green infrastructure can transform pollution-burdened cities into carbon sinks and liveable ecosystems.