Natural causes such as cyclones and waves, as well as human activities like construction, have led to nearly one-third of a large part of India's coastline to be eroded in the last 26 years, but almost an equal area has been added because of new sediment deposits, according to a government report. The National Centre for Coastal Research surveyed 6,031 kilometres of India's 7,517-kilometre coastline from 1990 to 2016 and found that 33 percent of it has witnessed erosion, most of it along the eastern coast facing the Bay of Bengal, with West Bengal recording the highest erosion. At the same time, 29 percent of the surveyed coastline saw an accretion, or gain in deposits.

"Erosion and accretion are complementary to each other. If the sand and sediments have drifted from one side, it must accumulate somewhere," said M V Ramana Murthy, director of NCCR and one of the authors of the report.  The report says that 2,156.43 kilometres of the country's surveyed coastline faced erosion, while 1,941.24 kilometres saw accretion on shore. It has long been known that the coastline is eroding, but officials needed to map and document it so that various agencies could take corrective measures, said M Rajeevan, Secretary in the Ministry of Earth Sciences and another co-author of the report.