Can sponge cities be the solution to India's increasing flooding problems?

44% of global disasters are linked to flooding, extreme weather patterns are likely to increase with climate change, and nature-based solutions to climate change can be 50 per cent more cost-effective

Heavy rainfall in northern India has caused widespread flooding, landslides, and significant damage to homes, structures, and food supplies. This raises concerns about the preparedness of cities to handle such large-scale disasters.

Yamuna River water levels have also reached an all-time high of 208.65 meters, surpassing the danger mark by 3.32 meters.

While emergency response teams like the National Disaster Response Force (NDRF) are present, there is a growing need for proactive measures to prevent disasters. This is where sponge cities come in, offering a potential solution to control the damage caused by floods.

 

What are sponge cities?

Sponge cities are urban areas designed with a permeable construction model that allows for the absorption and storage of rainwater.

 

The concept was first introduced in China in the early 2000s to address surface-level flooding in urban areas.

In 2014, pilot projects were initiated in several Chinese cities, with budgets ranging from 400 to 600 million yuan per city.

The primary objective of sponge cities is not only to prevent urban flooding but also to improve the ecology and biodiversity and address water resource shortages.

 

Why is this important?

As climate change leads to more extreme weather events like heavy rainfall and droughts, it has become crucial to integrate floodwater management systems in cities.

The World Meteorological Organisation reported that around 44 per cent of global weather-related disasters in August 2021 were linked to flooding.

This highlights the growing global phenomenon of flooding and the urgent need for preventive measures. Sponge cities rely on natural resources such as lakes, grass, and soil to create absorbent ground surfaces that allow rainwater to be stored.

Moreover, the World Economic Forum (WEF) found that 'nature-based solutions to climate change' were up to 50 per cent more cost-effective than engineered alternatives. In a report on sponge cities and their adoption in Chinese cities, the forum also added that this nature-based approach added 28 per cent more value than grey infrastructure.

Also Read: Housing ministry to organise national conclave on urban planning

 

Transforming cities into sponge cities

To transform cities into sponge cities, additional green spaces like parks, trees, and natural drainage systems need to be integrated. Increasing the presence of parks, greenery, and drainage systems enhances a city's "absorbency" and resilience to floods. Ground surfaces that mimic sponges can absorb rainwater, which is then naturally filtered by the soil and can recharge urban aquifers.

The collected water can be extracted through urban or peri-urban wells, treated, and reused for the city's water supply.

Digital mapping tools can assist cities in identifying suitable spaces for rainwater harvesting, ponds, and inner-city gardens, as well as understanding the associated risks of not implementing these measures.

 

Steps taken by cities so far

Many cities are already embracing the concept of sponge cities by adding green spaces that provide cleaner air, wildlife habitats, and relief from urban heat. 

Cities like Shanghai, New York, and Cardiff have improved river drainage, created plant-edged sidewalks, and developed inner-city gardens to enhance their sponginess, according to the United Nations Framework Convention on Climate Change (UNFCC).

 

Measuring "sponginess"

A recent study by Arup, reported on by UNFCC, utilised artificial intelligence to measure the "sponginess" of seven major cities. The study assessed the availability of natural space for rainwater absorption, including grass, trees, ponds, and lakes, as well as the presence of concrete, pavement, and buildings. Mumbai tied for third place with New York and Singapore, achieving a 30 per cent sponge city rating released in April 2022.

Arup is a multinational organisation dedicated to sustainable development. The firm has a collective of 18,000 designers, advisors and experts working across 140 countries. The report released by the firm added that around 700 million people lived in places where the maximum daily rainfall had increased.

 

The concept of sponge cities is still relatively new, and each urban area faces unique challenges that require tailored solutions based on the region's needs and biodiversity. However, the underlying principle remains the same: utilising nature-based solutions to tackle flooding. By transforming cities into sponge cities, we can create more resilient urban environments, better manage flood risks, and protect our communities from the increasing threats of climate change.