When the rains arrive, a city can change within hours. Roads turn into rivers, underpasses disappear under water, and overflowing drains bring traffic to a standstill. Yet, just months later, many of these same cities can be worrying about falling groundwater levels and water shortages.

This is the strange water paradox facing growing cities: too much water in one season, and too little in another.

Part of the problem is what lies beneath our feet. As cities expand, natural surfaces such as soil, wetlands, ponds and open spaces are replaced by concrete, asphalt and buildings. Rain that would once have slowly seeped into the ground now hits these hard surfaces and rushes into drains.

In India, the built-up area across the country’s 10 most populous cities grew by 52% between 2000 and 2015, according to a World Resources Institute study cited by the Good Food Movement. Much of this expansion happened over areas important for groundwater recharge.

So, what if cities were designed to absorb rain instead of simply trying to drain it away?

Think of a city like a sponge

Instead of treating every drop of rain as something that needs to disappear through a drain as quickly as possible, sponge-city planning gives water places to pause, seep into the ground, collect and slowly move away.

This can mean restoring lakes and wetlands, creating rain gardens, planting trees and vegetation, using permeable pavements that allow water to pass through, or even designing parks and playgrounds that can temporarily hold excess rain.

The science is actually quite simple: slow the water down.

Think about pouring water onto a tile versus a patch of soil. On a tile, water stays on the surface and runs towards a drain. Soil, on the other hand, can absorb some of that water.

Permeable pavements take this principle into an urban setting. Unlike conventional concrete or asphalt,........

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