20% of MMR coast is at risk of flooding

South Mumbai, eastern suburbs highly vulnerable to sea-level rise & storm surge because of unplanned development

About 20 per cent of Mumbai Metropolitan Region’s (MMR) coastline is highly vulnerable to flooding during natural disasters such as cyclonic storms and from a gradual rise in the sea level, a recent study by researchers has revealed.

Researchers have pointed out that unsustainable development, along with changes in land use and land cover, combined with the destruction of mangroves, wetlands and water bodies between 1976 and 2015, has made the low-lying topography of the MMR highly susceptible to sea level-induced flooding and coastal erosion.

The recent study on the characteristics of coastal vulnerability, correlated with the rise in sea-level along the Mumbai coast revealed that south Mumbai and eastern suburbs were highly vulnerable to the combination of sea-level rise and storm surge due to unplanned development.

Mumbai, Thane, Ratnagiri, and Raigad have been repeatedly identified as the cyclone hotspot districts in Maharashtra.

This area of study, spanning Mira-Bhayandar to the north of Mumbai, all the way to Alibaug towards the south, throws light on the fact that 50.75km of the MMR coast, south Mumbai and the eastern suburbs are highly vulnerable to floods. It also warns that under the direct impact of the increase in the sea-surface temperatures due to global warming, the rise in sea-level is expected to cause coastal floods annually.

While areas like Borivli and Andheri fall under the low-vulnerability scenario, other zones such as Gorai (Mumbai), Uttan, Uran, and Alibaug (all in Raigad) fall under moderate to high vulnerable ones. The findings of the study - ' Improving Outcomes For Socioeconomic Variables With Coastal Vulnerability Index Under Significant Sea-Level Rise: An Approach From Mumbai Coasts' – has been published earlier this month, in the peer-reviewed journal, Springer Nature. The research was conducted by a group of researchers from the Jawaharlal Nehru University (JNU), New Delhi, the Asian Institute of Technology, Thailand, the Deshapran College of Teachers Education - Medinipur, West Bengal and the School of Planning and Architecture, Bhopal. The research findings are proposed to be used as a guide in formulating policies to mitigate the impact of coastal flooding along Mumbai and MMR.

The lead author of the study and research fellow from The Asian Institute of Technology, Malay Kumar Pramanik, said: “We identified that unsustainable urbanisation, unplanned development, and huge land conversion, combined with the destruction of mangroves, reclamation of waterways with construction debris, inadequate drainage, overflow, and absence of natural protectors over the past four to five decades has made the region highly vulnerable to flooding.”

The researchers involved in the study pointed out that higher development activity combined with an increasing population per square kilometre, is leading to coastal erosion while activities such as tourism and fishing are contributing to an adverse influence along the coastal belt, especially along south Mumbai and the eastern suburbs. “While there is a need for sustainable development and alternative livelihood strategies, natural areas and ecosystems that have been degraded under developmental pressures need to be conserved and restored,” added Pramanik.

Pramanik pointed out that there were several policy gaps -- for instance, despite the Bombay High Court banning the hacking of mangroves in 2005, its on-ground implementation is completely missing. He also highlighted that developmental pressures, combined with a surge in population, had resulted in the dilution of the Coastal Regulation Zone (CRZ) rules from 1991 onwards. He said, “The reclamation of wetlands was also banned in 2014, but it has still not been stopped."

An analysis by McKinsey & Company Inc last year had shown that almost three million people living within a kilometre of Mumbai’s coastline were under threat from coastal flooding, storm surges and sea-level rise from now till 2050, with extreme weather events and storm surges to accelerate 1.5 times, with 100 km/hour wind speeds being the new normal.

P Velrasu, additional municipal commissioner (projects), said, “Our aim is to develop a Sponge City Master Plan, wherein chronic flooding spots will be addressed first. A consultant will be appointed to study and suggest flood control measures, including holding ponds. Separately, we are also in talks to appoint a Japanese consultant for building underground holding ponds. Some of the flood control measures include water-absorbent concrete, honeycomb water storage structures below the road and footpath, water storage structures in every big development, making porous and water impervious structures wherever possible.”