Building Resilient Cities


The Indian monsoon has become synonymous with flooding and disaster. Nature’s unpredictability and uncontrolled urbanization have combined to place around 2.6 million lives at risk and potentially cause hundreds of crores worth of property every year.

Various parts of Bihar, Assam, Arunachal Pradesh, Meghalaya, Mumbai, Karnataka, Rajasthan and Telangana experienced severe flooding due to the torrential rains this year. In Assam, the mighty Brahmaputra River swallowed the lives of more than 150 human beings and at least 225 animals in the Kaziranga National Park. Thousands of homes were submerged and hundreds of hectares of crops were destroyed.

The Indian Meteorological Department (IMD) says the country received 27% more rainfall than normal this August, the fourth-highest amount in the last 120 years. While governments may not always be able to control the floodwaters, they can certainly stop them from creating a disaster.

The most promising idea in this respect is the “sponge city”. The term refers to a city that is elastic and, like a sponge, can absorb severe environmental stress or natural disaster. In respect to flooding, it literally means the ability to absorb the excess water load. Key to this is the “sponge road” that can absorb, save, filter and purify water for later use.

Permeable asphalt is selected according to the rainfall characteristics of the project site. But porous materials used in roads can also be applied to riverbanks, lakes, the seaside and can play a huge role in sand stabilization, embankment reinforcement and water and air permeability. In urban areas, they can be used to absorb excess noise as well.

Porous roads have a huge advantage in helping to maintain the ecological balance. As a short-term application, road materials can contribute to drainage and flood control. In the long-term, they will cut down expenses and reduce the constant expansion of the urban piping network, prevent waterlogging and reduce flood damage. 

The sponge city project was first introduced in April 2012 at the “Low-Carbon Urban Development and Technology Forum” in Shenzhen, China. The concept was then successfully implemented across China. Most cities in China uses a combination of surface drainage and pipe drainage where the extensive use of hard concrete prevents surface penetration.

Inspired by China’s success with the technology, the Kerala government began experimenting with this new approach in 2020. As Kerala’s water resources minister K Krishnankutty told The Hindu, “The state will evolve a policy to use water resources effectively. The overall water requirements for various purposes such as drinking, irrigation, and power generation by 2030 would be around 1,000 thousand million cubic feet (tmc). However, only around 300tmc is available now.”

The department also planned to implement a ‘room for river’ program inspired by the Netherlands in Kuttanad. The ‘room for river’ project provides more space for the water body to manage extremely high water levels during floods. The surrounding areas can turn into natural sponges that can absorb excess water during floods.

As KA Joshy, chief engineer, design, research, and investigation wing of the Kerala irrigation department, explained, “The flood control dams planned in the state have multiple purposes such as irrigation, drinking water, and power generation. Unlike the existing dams which use only 8-10%, the proposed dams can utilize 25-30% cushion for flood control through spillway regulation.”

According to a 2019 article by NASA Earth Observatory, several states in India are facing critical drought conditions and water scarcity. Nearly 65% of the country’s reservoirs are running dry. One of the worst-hit areas is the state of Maharashtra, where six of the 17 reservoirs had dried out that year. Water conservation is the only long-term solution.


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