Mumbai's area has increased from 437.37 sq km in 1991 to 482 sq km now due to reclamations and years of silting by the sea. Land has been added largely on the eastern coast, with the western coast – which is exposed to stronger currents and winds – facing erosion.
An in-depth study on the impact of a century of reclamations in Mumbai has laid down lessons for future acquisition of land from the sea for ambitious infrastructure projects like the coastal road.
The study, conducted by the National Institute of Oceanography (NIO), has ascertained that the reclamation for part of the signature Bandra-Worli sea link (BWSL), has eroded the Mahim-Dadar beach by affecting wave and current patterns. The report, commissioned by state government thinktank Mumbai Transformation Support Unit (MTSU), has made suggestions for ensuring that the proposed 35.6-km coastal road between Nariman Point and Kandivali does not affect the ecology and erode the coastline further. The final report will be submitted to the state government this week.
Mumbai's area has increased from 437.37 sq km in 1991 to 482 sq km now due to reclamations and years of silting by the sea. Land has been added largely on the eastern coast, with the western coast – which is exposed to stronger currents and winds – facing erosion.
The study examines the impact of reclamation over the past century in Mumbai – originally an archipelago of seven islands forged into one land mass beginning with a series of reclamations since the colonial era – through library studies (up to 1970) and actual studies for the subsequent period.
"There is no significant impact of past reclamations on adjacent areas except in case of the BWSL," MTSU project director BC Khatua told dna. He added that the bund on the northern side of the bridge, which was meant to provide entry and exit to it, had affected the direction of the flow from the Mahim creek, changing it from a straight line to a circular manner, impacting the Dadar and Mahim beaches. This led to these beaches being eroded.
"The other reclamations were in a straight-line alignment with existing sea currents and waves. So they did not affect the coastal ecology or even the physiology," explained Khatua.
He added that the report, a preliminary draft of which was submitted to the MTSU steering committee last month, had noted the erosion and accretion of land and mangroves on the eastern and western coasts due to sea currents. The area under mangroves rose by 9.8 sq km from 1970 onwards.
"Mumbai's total area has increased… the BMC recognizes 458 sq km in the draft development plan (DP). The 1991 DP puts it at 437 sq km. This study has noted that Mumbai's area is 482 sq km," said Khatua, adding that this translated into a net gain of 45 sq km since 1991.
"The recommendations say that before reclamation, an assessment study must be conducted and if this is adverse, the reclamation should not be proceeded with. Where it is feasible and possible, the principle of not disturbing the wave flow and patterns must be followed. They have recommended straight line reclamations and not those which are zig-zag," he added.
Khatua said since the coastal road project involved reclamation from the sea, including some projections into the water, they had recommended to the BMC that these curves be smoothened out to prevent an adverse impact on the flow of waves. The study has recommended that underwater bunds be created at Dadar and Mahim to stop sand erosion and capture sand being brought in by the high tide. Sand from outside may be added to the beaches to nurture them.
Environmentalist Stalin D of Vanashakti pointed out that "any kind of reclamation is bound to alter the tidal pattern and intensity (of the currents)" and pointed to how even the Juhu and Versova beaches were getting eroded. He said the solution to reclamation, which he said was used by the corporate sector to cut costs, was constructing roads or bridges on stilts or building suspended bridges.
Waves of reclamation
As Mumbai evolved from a collection of fishing villages to a vibrant metropolis, it has seen multiple waves of reclamation. This includes one of the first in the 1700s at Umerkhadi to control malaria, constructing the Colaba (1838) and Mahim-Sion causeways, building railways and the port and creating business districts like Ballard estate and recently, the Bandra Kurla Complex. Slums and housing projects also sprouted on reclaimed land. Later day reclamations include the controversial Backbay Reclamation project during the tenure of then chief minister Vasantrao Naik, Bandra and the Lokhandwala complex
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