‘The easiest way to control urban flooding is to give water more space’ | Latest News Delhi

Parts of Delhi were flooded this monsoon, with the Yamuna forcefully reclaiming some of the territory it lost to hyper-urbanisation. However, the national capital is not an exception. Cities across the world are suffering a similar fate due to record-breaking rain and mindless concretisation. China, the leader of the global pack in its obsession with growth and urbanisation, has, however, tried course correction after 79 casualties in the 2012 Beijing floods.

Parts of Delhi were flooded this monsoon, with the Yamuna forcefully reclaiming some of the territory it lost to hyper-urbanisation. (HT Photo)
Parts of Delhi were flooded this monsoon, with the Yamuna forcefully reclaiming some of the territory it lost to hyper-urbanisation. (HT Photo)

On President Xi Jinping’s intervention, China, in 2015, launched the Sponge Cities project to develop storage ponds and wetlands and create permeable road infrastructure to soak stormwater into the ground. But two years ago, when Zhengzhou and cities across north China, including Beijing this year, saw some of the worst floods, critics questioned the project’s efficacy in dealing with such a high volume of rain.

Chinese landscape architect and Peking University professor Kongjian Yu, who pioneered the concept, told Shivani Singh that it is wrong to judge a project that is still in the nascent stage, and needs to cover not just entire cities but regions, nations and perhaps the planet. Though ambitious, the idea of living with water, he says, is not new to ancient civilisations such as those in India and China.

Edited excerpts:

The 2021 floods in Zhengzhou, one of the spongiest Chinese cities, claimed 380 lives and caused a massive loss of infrastructure. This year again, many cities in northern China saw devastating floods. Critics say sponge cities alone cannot handle intense rainfall and flash floods. Do you agree?

You want (aspire) to be an ecological city. But suddenly (before you become one), your city has some ecological problems. Will you say the ecological city didn’t work? It is the same misconception… that Zhengzhou is a sponge city, which it is not.

A sponge city is a nature-based, water-resilient city meant to handle extreme weather. The usual (water discharge) can be handled by the grey drainage and flood control infrastructure. But then, a sponge city is a systematic concept that goes beyond the city’s boundaries. If the water comes (to the city) from another place, we should go to the watershed. Floods can be at a regional, national or even a global scale. If climate change means that the whole globe will be flooded, then we have to solve the problem of the planet.

But is it possible to address the problem at so many levels?

It is possible because climate change hasn’t increased the amount of water. It has changed the precipitation pattern. In the flood season, you have more (intense) floods but at the same time, you have more droughts. So why don’t we store water in the ground? The planet is 30% land, and the rest, 70%, is water. The aquifer (groundwater reserve) is short of water. Yet during the monsoon-type flooding (seasonal flood), we see huge amounts of water being flushed away by our engineering projects. We have channelised rivers and have built dams. If the dam overflows or develops cracks, it can destroy cities.

This grey infrastructure — concrete, pipes and reservoirs — cannot adapt to climate change. They are designed based on mild climates (that prevailed during the Industrial Revolution), such as in England or the Netherlands. The model of Indian urbanisation and infrastructure is colonial, taken from England. Meanwhile, the Indian tradition and knowledge of adaptation to climate change are considered primitive and (based on) agricultural (methods).

Modernisation is a copied Western model of urbanisation and infrastructure development dumped onto a monsoon climate. All modern cities built based on this industrialised civilisation failed because they copied the model, which was not developed in Asia.

But today, with climate change, even Western countries have failed. New York’s drainage system was designed based on a maximum of two inches of precipitation daily. Now suddenly, they have five inches of daily precipitation. Globally, the modern infrastructure based on industrial technologies such as concrete, steel and pump systems that require intensive energy use failed because of climate change.

On the other hand, a sponge city is based on the monsoon climate and 2,000-5,000 years of experience and knowledge of adaptation. When we talk about climate change, we talk about a monsoon climate and a very dry season. It’s not about five inches of precipitation. It’s about 100 inches of precipitation on some days. And when you have a very dry season, you have three or four months without precipitation. That’s why sponge city is a model based on climate change, adaptation, and the regulation of stormwater adaptation to the monsoon.

The sponge city project was officially adopted in 2015. Has it shown any positive results yet?

We have about 70 cities in China that are experimenting with sponge cities. But it’s not a whole city. This experiment covers only a certain area. However, these experiments show that sponge cities have been successful. Then why did Beijing or Zhengzhou get flooded again? Beijing is a big city, and the sponge city experiment is just at the beginning. When Beijing faced floods in 2012, when the project had not yet started, 79 people died. This year, Beijing had a more severe flood in terms of precipitation. But the death toll and damage have been much less. This is just one example. But then the area that has been tested is still very small.

My company Turenscape has undertaken over 600 projects, that include removing concrete from rivers and roads, and increasing green space for holding water. These projects have performed well in terms of regulating stormwater (run-offs). But it is still a very small proportion compared to our massive scale of urbanised areas.

A flooded road in Zhengzhou, China in July 2021.(Reuters)
A flooded road in Zhengzhou, China in July 2021.(Reuters)

What needs to be done to scale up the project for more comprehensive coverage?

The implementation of the sponge city project is still at the early stage and has been patchy, though the (Chinese) central government has been pushing this for the past decade. It confronts several obstacles, the most important being the mentality. It’s business as usual regarding flood control efforts and urban drainage engineering.

Decision-makers must be brave and demonstrate a broader vision to break this (mindset). Hydrological and civil engineering professionals need to be re-educated. All the existing code systems associated with water management and flood control must be rewritten. Legislative backing is necessary for this. It is virtually an ecological revolution. It needs shovelling the university programmes, the professional practice guidelines and the infrastructure investment system.

Sponge cities are a long-term project but urban areas facing flooding need immediate solutions. Do you think nature-based solutions like these must be complemented with hardware – pipes and pumps?

We already have excessive hardware and concrete infrastructure. Look at what happened in Libya last month — a dam collapsed, killing thousands of people. Look at New Orleans. We have dams everywhere.

But this grey infrastructure (designed for a 50–100-year flood-return period) will fail anyway (if more forceful floods return). Will you continue to build these dams, which come with huge investments? Or do you want an alternative – a nature-based sponge city system – which comes with less money and takes less time to develop? I can finish a huge Sponge Cities project in one year. A concrete wall may take two to three years.

It is not that I want to demolish all concrete immediately. It takes time to transform grey (concrete and steel infrastructure) into green. But it doesn’t have to be 200 years.

Also, you cannot solve the problem immediately for the whole city. But we do have immediate solutions compared to building a concrete wall. The easiest is to give water more space. For example, don’t build a flood wall along the river. India, Bangladesh and most parts of Southeast Asia are urbanising very fast. So, whatever is being built should be built for safety. Find a safe location for building a new city or town. Don’t build a flood wall because the city will get flooded someday and, like it happened in Libya, this flood wall will collapse.

Kongjian Yu(HT Photo)
Kongjian Yu(HT Photo)

You’re saying that we need to be careful about how we build infrastructure, now and in the future. But much of our construction in Indian and Chinese cities has already happened. How do you remove all this?

Presuming that the rate of urbanisation is 40% in India, 60% of the country is yet to urbanise. The immediate question is: what path should we take to urbanise our countryside? Where to build as a city? Should you build a wall to protect your city?

In a low area, which has a high risk of flooding, you have to build a sponge city instead of a wall and gradually remove the wall. But to do this, you need to find a wise planner.

Cities are over-paved, waterways are over-paved. Water is not greedy. 20-30% of the total urban area is enough if planned and designed properly and turned into green sponges; it will solve the problem of urban floods. Additionally, roofs, parking lots, community gardens and backyards can also function as sponges. However, handling the regional flood would require a regional sponge system.

Development is often linked to brick, mortar and steel. So, what made China, which is on the path of hyper-urbanisation, change tack to explore this nature-based approach?

Development certainly doesn’t mean more pavements, more concrete, more burning of coal, more use of electricity. Development means a better life, a better environment and higher incomes. By (prescribing) nature-based solutions, I don’t mean we should return to primitive villages or agricultural civilisation.

I mean that ancient cultures, such as India’s and China’s, have accumulated knowledge to adapt to the monsoon climate. We can upgrade that wisdom by integrating it with modern technology and science. We can have better solutions than just copying the grey infrastructure, which has proven to fail with the changing climate. The alternative is Sponge City.

I don’t mean that we should not have concrete. We have to make wise use of concrete. We have to allow nature to perform the maximum. So, it is an idea based on our past and what we have learnt from the developed countries for the future, which is more ecological, more climate-adaptive… and more resilient city infrastructure.

The problem of urban flooding is getting worse in India. Much of the water-bodies, floodplains, natural stormwater channels and green spaces have been lost to urbanisation. It is difficult to relocate people living here. How do we then reclaim these spaces for nature-based solutions? What would you advise Indian cities planning to emulate the Sponge Cities model?

This is a critical time for India, like it was for China 20 years ago. If you keep following conventional models – paving the land and channelising the river – you’ll have a problem because Indian cities will have more people coming into the cities.

Second, you have to solve the urban problem within the urban boundary. In India, you have high precipitation and a long dry season. You need to keep (store) water in the ground, on the roof, and in the backyard. There is enough space in a city like Delhi to do that. You need to increase permeable spaces as much as possible.

Third is addressing the problem of regional floods by making space for water. If the Ganga gets flooded, you must let the flood water disperse seasonally in the adjoining farmlands. This will solve the problem of regional floods and keep your cities safe.

Some densely populated cities in India, such as Chennai, are on the coast, facing the challenge of a rise in the sea level. To stop water coming into the cities, the conventional approach is to build a sea wall. But if you don’t let the water permeate into the ground and discharge the flood water into the ocean, the sea level will continue to rise and your wall will have to keep going higher. It would be like drinking poisonous wine to quench thirst. The immediate solution is to keep (store) water in the ground (aquifers). And even a slow change (nature-based solution) is immediate. As we say in Chinese philosophy, a long journey begins with a footstep.

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