Overview: Framework for Quantitative Assessment of Urban-Blue-and-Green-Spaces in a High-density Megacity

Urban-blue-and-green-spaces (UBGS) comprising waterbodies and green spaces are intrinsic to the urban environment due to their immense ecological, social, economic, and health benefits. Owing to high population densities, megacities in countries with emerging economies are losing their natural areas, adversely affecting the urban environment. This article studies the current built-open space dynamics and proposes a conceptual framework for the quantitative assessment of UBGS in the Indian megacity of Kolkata at the smallest administrative unit called wards. Results show that the available UBGS is 11.51% of the total area and 5.08 sq.m per inhabitant, both of which are far below the national and international urban planning guidelines. The wards are appraised for two indices, UBGS Distribution Index and UBGS Availability Index, based on spatio-physical distribution and per inhabitant availability, respectively, comparing them with the Indian urban planning standards. The indices represent the actual shortfall of UBGS in each ward in terms of minimum requirements as per national standards The present unequal distribution of UBGS in the city is a matter of social and environmental justice that needs to be addressed. The indices show a correlation of 0.6688. This framework can help decision-makers protect, preserve, and promote the city's UBGS by adopting a bottom-up approach to solve local issues and providing safe and socially inclusive public spaces for all sections of society.