What does Mumbai’s experience of the downpour of 2005 tell us about what might, or might not, happen if a major storm hits the city? The events will, of course, unfold very differently: to start with, a cyclone will arrive not with a few hours’ notice, as was the case with the deluges, but after a warning period of several days. Storms are now so closely tracked, from the time they form onwards, that there is usually an interval of a few days when emergency measures can be put in place.

Of these emergency measures, probably the most effective is evacuation. In historically cyclone-prone areas, like eastern India and Bangladesh, systems have been set up to move millions of people away from the coast when a major storm approaches; these measures have dramatically reduced casualties in recent years. But the increase in cyclonic activity in the Arabian Sea is so recent that there has yet been no need for large-scale evacuations on the subcontinent’s west coast.

Whether such evacuations could be organised at all is an open question. Mumbai has been lucky not to have been hit by a major storm in more than a century; perhaps for that reason the possibility appears not to have been taken adequately into account in planning for disasters. Moreover, here, ‘as in most megacities, disaster management is focused on post-disaster response’.

In Mumbai, disaster planning seems to have been guided largely by concerns about events that occur with little or no warning, like earthquakes and deluges: evacuations usually follow rather than precede disasters of this kind. With a cyclone, given a lead-up period of several days, it would not be logistically impossible to evacuate large parts of the city before the storm’s arrival: its rail and port facilities would certainly be able to move millions of people to safe locations on the mainland.

But in order to succeed, such an evacuation would require years of planning and preparation; people in at-risk areas would also need to be educated about the dangers to which they might be exposed. And that exactly is the rub – for in Mumbai, as in Miami and many other coastal cities, these are often the very areas in which expensive new construction projects are located.

Property values would almost certainly decline if residents were to be warned of possible risks – which is why builders and developers are sure to resist efforts to disseminate disaster-related information. One consequence of the last two decades of globalisation is that real estate interests have acquired enormous power, not just in Mumbai but around the world; very few civic bodies, especially in the developing world, can hope to prevail against construction lobbies, even where it concerns public safety.

The reality is that “growth” in many coastal cities around the world now depends on ensuring that a blind eye is turned towards risk.

Even with extensive planning and preparation the evacuation of a vast city is a formidable task, and not only for logistical reasons. The experience of New Orleans in the days before Hurricane Katrina, or of New York before Sandy, or the city of Tacloban before Haiyan, tells us that despite the most dire warnings large numbers of people will stay behind; even mandatory evacuation orders will be disregarded by many. In the case of a megacity like Mumbai this means that hundreds of thousands, if not millions, will find themselves in harm’s way when a cyclone makes landfall. Many will, no doubt, assume that having dealt with the floods of the recent past they will also be able to ride out a storm.

But the impact of a Category 4 or 5 cyclone will be very different from anything that Mumbai has experienced in living memory. During the deluges of 2005 and 2015 rain fell heavily on some parts of the city and lightly on others: the northern suburbs bore the brunt of the rainfall in both cases. The effects of the flooding were also most powerfully felt in low-lying areas and by the residents of ground-level houses and apartments; people living at higher elevations, and on the upper storeys of tall buildings, were not as badly affected.

But the winds of a cyclone will spare neither low nor high; if anything, the blast will be felt most keenly by those at higher elevations. Many of Mumbai’s tall buildings have large glass windows; few, if any, are reinforced. In a cyclone, these exposed expanses of glass will have to withstand not just hurricane-strength winds but also flying debris.

Many of the dwellings in Mumbai’s informal settlements have roofs made of metal sheets and corrugated iron; cyclone-force winds will turn these, and the thousands of billboards that encrust the city, into deadly projectiles, hurling them with great force at the glass-wrapped towers that soar above the city.

Nor will a cyclone overlook those parts of the city that were spared the worst of the floods; to the contrary they will probably be hit first and hardest.

The cyclones that have struck the west coast of India in the past have all travelled upwards on a north-easterly tack, from the southern quadrant of the Arabian Sea. A cyclone moving in this direction would run straight into south Mumbai, where many essential civic and national institutions are located.

The southernmost tip of Mumbai consists of a tongue of low-lying land, much of it reclaimed; several important military and naval installations are situated there, as is one of the country’s most important scientific bodies – the Tata Institute of Fundamental Research. A storm surge of 2 or 3 metres would put much of this area under water; single-storey buildings may be submerged almost to the roof. And an even higher surge is possible.

Not far from here lie the areas in which the city’s most famous landmarks and institutions are located: most notably, the iconic Marine Drive, with its sea-facing hotels, famous for their sunset views, and its necklace-like row of art deco buildings. All of this sits on reclaimed land; at high tide waves often pour over the sea wall. A storm surge would be barely impeded as it swept over and advanced eastward.

A distance of about 4 kilometres separates south Mumbai’s two sea-facing shorelines. Situated on the east side are the city’s port facilities, the legendary Taj Mahal Hotel, and the plaza of the Gateway of India, which is already increasingly prone to flooding. Beyond lies a much-used fishing port: any vessels that had not been moved to safe locations would be seized by the storm surge and swept towards the Gateway of India and the Taj Hotel.

At this point waves would be pouring into south Mumbai from both its sea-facing shorelines; it is not inconceivable that the two fronts of the storm surge would meet and merge.

In that case the hills and promontories of south Mumbai would once again become islands, rising out of a wildly agitated expanse of water. Also visible above the waves would be the upper storeys of many of the city’s most important institutions: the Town Hall, Vidhan Sabha, the Chhatrapati Shivaji Railway Terminus, the towering headquarters of the Reserve Bank of India and the skyscraper that houses India’s largest and most important stock exchange.

Much of south Mumbai is low-lying; even after the passing of the cyclone many neighbourhoods would probably be waterlogged for several days; this will be true of other parts of the city as well. If the roads and rail lines are cut for any length of time, food and water shortages may develop, possibly leading to civil unrest.

In Mumbai, waterlogging often leads to the spread of illness and disease: the city’s health infrastructure was intended to cater to a population of about half its present size; its municipal hospitals have only 40,000 beds. Since many hospitals will have been evacuated before the storm, it may be difficult for the sick and injured to get medical attention. If Mumbai’s stock exchange and Reserve Bank are rendered inoperative, then India’s financial and commercial systems may be paralysed.

But there is another possibility, yet more frightening. Of the world’s megacities, Mumbai is one of the few that has a nuclear facility within its urban limits: the Bhabha Atomic Research Centre at Trombay. To the north, at Tarapur, 94 kilometres from the city’s periphery, lies another nuclear facility. Both these plants sit right upon the shoreline, as do many other nuclear installations around the world: these locations were chosen in order to give them easy access to water.

With climate change many nuclear plants around the world are now threatened by rising seas. An article in the Bulletin of the Atomic Scientists notes: ‘During massive storms . . . there is a greatly increased chance of the loss of power at a nuclear power plant, which significantly contributes to safety risks.’ Essential cooling systems could fail; safety systems could be damaged; contaminants could seep into the plant and radioactive water could leak out, as happened at the Fukushima Daiichi plant.

What threats might a major storm pose for nuclear plants like those in Mumbai’s vicinity?

I addressed this question to a nuclear safety expert, MV Ramana, of the Program on Science and Global Security at Princeton University. His answer was as follows: “My biggest concerns have to do with the tanks in which liquid radioactive waste is stored. These tanks contain, in high concentrations, radioactive fission products and produce a lot of heat due to radioactive decay; explosive chemicals can also be produced in these tanks, in particular hydrogen gas. Typically waste storage facilities include several safety systems to prevent explosions. During major storms, however, some or all of these systems could be simultaneously disabled: cascading failures could make it difficult for workers to carry out any repairs – this is assuming that there will be any workers available and capable of undertaking repairs during a major storm. An explosion at such a tank, depending on the energy of the explosion and the exact weather conditions, could lead to the dispersal of radioactivity over hundreds of square kilometres; this in turn could require mass evacuations or the long-term cessation of agriculture in regions of high contamination.”

Fortunately, the chances of a cyclone hitting Mumbai are small in any given year. But there is no doubt whatsoever of the threats that will confront the city because of other climate change impacts: increased precipitation and rising sea levels. If there are substantial increases in rainfall over the next few decades, as climate models predict, then damaging floods will become more frequent. As for sea levels, if they rise by 1 metre or more by the end of the century, as some climate scientists fear they might, then some parts of south Mumbai will gradually become uninhabitable.

The Great Derangement

Excerpted with permission from The Great Derangement, Amitav Ghosh, Allen Lane.