Thread by @rocksea

1/ With climate change, the storyline has changed for Mumbai and the coastline of India. This thread discusses how storms surge from intense cyclones, heavy rains, and sea-level rise are all overlapping—to create prolonged large-scale floods.
#MumbaiMustPrepare @MumbaisMagic

2/ Arabian Sea is brewing more intense cyclones than ever. Tauktae was the most intense cyclone (220 km/hr) that came very close to Mumbai. Cyclones drive storm surges—huge waves (5 m high) that push water onto the land, flooding the coast.
◉ Flood = storm surge

3/ Cyclones are bringing more rains than ever. Global warming has made more water available as warm air holds more moisture. Tauktae brought heavy rains of 230 mm in a day (SantaCruz, Mumbai), an all-time record for May.
◉ Flood = storm surge + rain water.

4/ Sea level rise is at a fast pace along the coast of Mumbai, at about 3 cm per decade now. This may be 5 cm in the coming decades, which means half a meter underwater in a century.
◉ Flood = storm surge + rain water + sea level rise.

5/ These floods occasionally ride on a high tide, compounding the impact and prolonging the floods inland. This happened with Cyclone Yaas on Odisha coast, despite it being a moderately severe cyclone (120 km/hr).
◉ Flood = storm surge + rain water + sea level rise + high tide.

6/ We always forget to add that the coastal population is increasing. Increasing exposure due to the rising population is one of the most important causes for losses due to increased vulnerability to climate change.
Mumbai population = 21 Million in 2021 and 42 million in 2050.

7/ As cyclone season gets over, Mumbai should get ready for heavy rains. Our research shows a threefold rise in widespread extreme rains that cause largescale floods, not only along the west coast but also central and north/east parts of India.
nature.com/articles/s4146…

8/ Unequal scenes.
Where are the rivers, flood plains, and mangroves that should be absorbing the Mumbai floods? As strong winds, rains, and floods lash out, will it be those shacks that get flooded first or will it be their blue tarpaulin roofs that get blown away?

9/ Improved monitoring, forecasts and disaster management have brought down the number of deaths. But climate change has brought new challenges with rapidly intensifying cyclones and overlapping floods. Need to further improve our monitoring & forecasting
doi.org/10.1175/BAMS-D…

10/ We can’t wait for forecasts every time for evacuating people. We cannot evacuate houses, cars, infrastructure, and ecosystems. Cyclones, heavy rains, sea level, and overlapping floods are projected to intensify along the west coast in response to continuing carbon emissions.

11/ What we need to do first is a risk assessment that can demarcate the regions where the risks of floods, cyclones, and severe weather events are largest. Based on that, we need to disaster-proof these regions, using both natural and artificial defenses, and other methods.

12/ Bring back the mangroves. Mangroves act as the sponge of the city, breaking the flow of flash floods and absorbing the impact. Mumbai lost a lot of its mangrove cover and freshwater drainages, and we need to recover them. BKC was built over hectares of mangroves.