An increase in paved surfaces such as roads and buildings irreversibly changes natural infrastructure, ecosystems, and hydrological surface and subsurface flows in urban areas. The loss of natural infrastructure has complex interlinked consequences such as reduced groundwater recharge leading to dropping aquifer levels and increased rainwater runoff leading to higher flood risk. In addition, the high pressure of development in and around urban centers leads to new development being sited on high-risk, vulnerable zones such as floodplains, lake beds, and low-lying areas.

In this working paper, we examine the relationship between urbanization (increase in built-up area) and natural infrastructure change (in blue-green cover) across India’s 10 most populated cities. We look at all development in the urban region, not distinguishing between formal and informal settlements.

We recommend that state and city authorities adopt an integrated urban blue-green approach to urban planning and development regulation using spatial and on-ground evidence to conserve and restore natural spaces, water bodies, aquifers, and other ecosystems to increase urban resilience.

Key Findings:

Between 2000 and 2015, the built-up area in these 10 cities increased on average by 47 percent and 134 percent within 0–20 km of the city center (core) and 20–50 km (periphery), respectively.

Surface water lost across the 10 cities between 2000 and 2015 is estimated to be 307 sq. km (square kilometers), a 15 percent decrease.

It is estimated that 44 percent (1,177 sq. km) of new development between 2000 and 2015 has come up on areas with high or very high recharge potential (in the 0–50 km urban region of the 10 study cities).

Executive Summary:

Urbanization all over the world is typically associated with increases in the spatial extent of urban built-up areas. India remains an urbanizing nation and is expected to double its urban population from about 400 million in 2018 to about 800 million by 2050. The extent of urban areas is set to increase dramatically to support the growing population, with estimates suggesting that 70 to 80 percent of the infrastructure needed in 2030 is yet to be built. All this new construction will have profound and far-reaching impacts on urban centers and their surroundings. However, there is limited research and forecasting on how these new developments interact with and impact natural infrastructure and ecological and hydrological systems.

About This Working Paper

This working paper seeks to expand our knowledge of urbanization and its impacts on the surrounding natural landscapes in India. We study the urbanized region of India’s 10 most populated cities to examine the relationship between urban (built-up) expansion and changes in blue-green infrastructure such as surface waters, green cover, and recharge zones. Improving the interactions between urbanization and natural infrastructure in these 10 cities can significantly impact the well-being of about 30 percent of India’s urban population.

Remote sensing data and satellite imagery are used to monitor urbanization and changes in blue-green infrastructure between 2000 and 2015 in the 10 study cities. The cities studied are Ahmedabad, Bengaluru, Chennai, Delhi, Hyderabad, Jaipur, Kolkata, Mumbai, Pune, and Surat. The correlation between urbanization and natural infrastructure is studied in two spatial intervals of 20 km (0–20 km) and 50 km (20–50 km) from the center of each of the study cities.


Thumbnail image by Mike Prince/ Flickr