Blue-Green Infrastructure (BGI) network in urban areas for sustainable storm water management: A geospatial approach

In a natural landscape, when rainfall reaches the Earth’s surface, water either percolates into the ground or it flows as run-off finally reaching a water body such as a lake or a river. Due to rapid urbanization, the natural landcover in the cities is being replaced with impervious surfaces which significantly alters the natural patterns and processes of urban landscape resulting in mismanagement of storm water and hence the flooding issues. Integrated Blue-Green Infrastructure (BGI), a landscape conservation approach with nested networks of blue and green spaces (permeable pavements, bioswales, rain gardens, urban tree cover, small ponds and wetlands) can provide an alternative approach to conventional storm water management along with its multiple environmental benefits. The objective of this paper is to develop a geospatial technology-based approach for the identification of BGI network by employing graph theory and gravity model for sustainable storm water management in the city of Ahmedabad, India. The study introduces a replicable approach by integrating five key criteria i.e., slope, drainage density, land cover, hydrologic soil group and proximity to roads for Suitability Analysis, selecting core patches as nodes in a GIS environment and identifying corridors by employing the least cost path function followed by assessment of selected corridors using gravity model. Analysis of land surface characteristics reveals that Ahmedabad has a high suitability for the implementation of BGI. A variety of blue and green open spaces throughout the city such as parks, gardens and lakes form the node which are connected by a network of corridors developed by the least cost path model and gravity model. The methods and practices adopted in this research represented an innovative approach for the implementation of BGI networks for storm water management in an urban landscape.