20% of MMR’s coastline highly susceptible to flooding: Study
A stretch of 50.75km along the coast of the Mumbai Metropolitan Region (MMR) is highly susceptible to flooding because of unsustainable development, finds a recent study on coastal vulnerability by a group of researchers from a cohort of institutes.
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, have made the low-lying topography of MMR highly susceptible to sea level-induced flooding and coastal erosion, find researchers.
The study “Improving outcomes for socioeconomic variables with coastal vulnerability index under significant sea-level rise: an approach from Mumbai coasts” was published in the global peer-reviewed journal Springer Nature on February 5.
A group of three researchers – Malay Kumar Pramanik from Jawaharlal Nehru University, New Delhi and fellow from the Asian Institute of Technology, Thailand; Poli Dash from Deshapran College of Teachers Education, Medinipur, West Bengal, and Dimple Behal from the School of Planning and Architecture, Bhopal – studied the coastline from Mira Bhayander to Alibag.
They studied a total of 274.1km, of which 50.75km (almost 20%) was considered to be very-highly vulnerable, based on 12 geological, physical and socio-economic variables. Another 60.91km had moderate vulnerability and 55.83km of the shoreline surveyed had very-low vulnerability.
Researchers found that the coastline in the eastern suburbs, including Kurla, Deonar, Shivaji Nagar, Trombay Koliwada and the western section of the Thane creek, was very susceptible to flooding. While areas like Borivli and Andheri fell under the low vulnerability scenario, other zones such as Gorai, Uttan, Uran, and Alibaug fell under the moderate to high vulnerability scenario.
“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,” said Pramanik, lead author of the study.
The researchers involved in this study suggested that higher development activity combined with an increasing population per square kilometre was 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.
The study has warned that under the direct impact of the increase in sea surface temperatures due to global warming, the rise in sea level is expected to cause coastal floods annually. The findings are along the lines of a previous international study by an American scientific research organisation, Climate Central, in October 2019, which found that large portions of the city’s suburbs and south Mumbai may be underwater by 2050 if emissions are not kept in check.
“While there is a need for sustainable development and alternate livelihood strategies, natural areas and ecosystems that have been degraded under developmental pressures need to be conserved and restored,” said Pramanik, adding that the research findings will help formulate policies to mitigate the impacts of coastal flooding along Mumbai.
Dr Roxy Mathew Koll, senior scientist, Indian Institute of Tropical Management, Pune, who was not part of the study, said, “We need policies and action plans at the local level, based on conditions, geography, population, etc. Action plans should integrate flood forecasting with tidal information so we can have early warning systems. When making plans, we also need to think of both artificial protections as well as natural defences. Mangroves are a low-cost protection measure – they break the flow of floods, absorb their impacts. We should also be trying measures like bio-drainage, networks of canals that act as drainage during floods and can retain rainwater during dry periods.”
P Velrasu, additional municipal commissioner (projects), Brihanmumbai Municipal Corporation (BMC), said, “We aim to develop a Sponge City Master Plan wherein chronic flood spots need to 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 to build underground holding ponds. Some of the flood control measures include water absorbent concrete, honeycomb water storage structures below roads and footpaths, water storage structures in each big development, building porous structures wherever possible.”