Mumbai and Kolkata face the wrath of sea-level rise
Just as a surprise burst of showers sent Mumbaikars scrambling around on Friday, you could hear Axl Rose, Slash and co belting out November Rain in your mind only to be interrupted by the cab driver ranting about how we have brought all this upon ourselves by felling trees and building a concrete mess. This coincided with the Delhi government shutting down schools until the 5th of November due to deteriorating air quality conditions. If you thought that things couldn’t get worse, a new research paper – New Elevation Data Triple Estimates Of Global Vulnerability To Sea-level Rise And Coastal Flooding by Scott A. Kulp and Benjamin H. Strauss says “We have severely underestimated just how much global coastlines are in danger from rising sea levels”. To the extent that large parts of Mumbai and Kolkata could be underwater in as little as 30yrs. Turns out that all these years we have been overestimating the elevation of land – hence the startling finding that at the current pace of rising water levels, we would be submerged much sooner than we thought.
“Take India, for example: Even by moderate estimates, by 2050, 36 million people (going by the 2010 census) living in coastal areas will be at risk from annual flooding due to sea-level rise; the previous estimate was five million. By the end of the century, these areas will be permanently underwater, and the number of affected people would go up to 44 million; much of Mumbai and Kolkata, as well as Odisha’s coast, coastal Gujarat around Surat and the Sunderbans in Bengal will be badly affected.
…The reason for this worse-than-imagined scenario is based on the computational model developed by Kulp and Strauss. Currently, coastal elevation data is primarily measured using Nasa’s Shuttle Radar Topography Mission (SRTM). The authors found the data to be unreliable, in that SRTM was seen to overestimate global coastal elevations by as much as 6ft. This went up to 8-15ft in some places around the world. To negate the mistakes in estimates, they devised the CoastalDEM (digital elevation model), using machine learning for truer coastal elevations. The results are astonishing.
Imagine a Mumbai that, by 2050, will be subjected to severe annual floods, reducing the city and its immediate neighbourhoods to the islands they once were. According to interactive maps on the Climate Central website, a future scenario of limited mitigation and no adaptation would turn areas like Colaba, Malabar Hill, Bandra West and the Sanjay Gandhi National Park into isolated patches rising above the flood. Much of the city, which is below the tideline, will be overwhelmed, all the way up past Vasai and Nala Sopara to the north, and Navi Mumbai and Dombivili to the east. Sensitive infrastructure, like the reactors of the Bhabha Atomic Centre, would be at risk.”