A total of 250.21 sq km along India’s coast was lost over 15 years because of the rising sea level, according to a study by the Indian Space Research Organisation (ISRO) and Central Water Commission (CWC).
A team of 10 scientists from the Space Application Centre in Ahmedabad -- a key unit of ISRO -- and the CWC under the water resources ministry studied changes along the country’s 8,414km shoreline, including those of islands such as Andaman and Nicobar and Lakshadweep.
The team compared satellite pictures taken between the periods 1989-1991 and 2004-2006. During this time, the coastline was battered by several natural disasters such as the 1999 super cyclone, the 2004 tsunami and the 2013 severe cyclone Phailin.
The Nicobar Islands lost the maximum area of around 94 sq km. States such as Maharashtra, Andhra Pradesh, Odisha and West Bengal and the Lakshadweep and Nicobar Islands too lost land to sea erosion.
However, a total of 177.15 sq km was accreted or accumulated along the coast during the same period, the study revealed. After taking the accretion into account, the net loss of land because of erosion was 73 sq km.
“The results show that 3,829 km (45.5%) of the coast is under erosion, 3,004 km (35.7%) is getting accreted, while 1,581 km (18.8%) of the coast is more or less stable in nature,” said AS Rajawat, a senior scientist with the Space Application Centre in Ahmedabad who led the study.
The rising sea level was one of the major reasons for the erosion along the coastline, while other factors responsible for the phenomenon were unbridled and unplanned human activities, local coastal subsidence, storm surge and the 2004 tsunami.
It was seen that the Andaman and Nicobar islands lost a significant amount of land in the tsunami.
On the other hand, the building of new beaches and sand and silt deposits were the main reasons for the accretion of land. Some states such as Tamil Nadu, Gujarat, Maharashtra and Kerala accreted huge areas of land due to deposition. West Bengal accreted the least area while it lost around 11 sq km.
Though there are studies and an inventory of erosion along the Indian coast, they are region-specific and inadequate for planning requirements at the national level. This is probably the first time that shoreline changes for the entire Indian coast were mapped in detail.
“While West Bengal has lost around 11.63 sq km, it has gained around 1.52 sq km. The net loss for West Bengal is around 10 sq km. Out of the total shoreline of 282 km in West Bengal, 115 km is getting eroded,” said Rajawat.
The study was undertaken on the recommendation of the Coastal Protection and Development Advisory Committee, the apex body for planning coastal protection measures in India.
Earlier, studies by the National Centre for Sustainable Coastal Management under the union environment, forests and climate change ministry have shown that more than 40% of India’s coastline is eroding at a much higher rate than previously estimated.
In a recent study based on satellite data and tidal observations, scientists at the National Institute of Oceanography in Goa showed that the sea level is rising by 3.2 mm every year since the early 1990s. The sea level along the northern and eastern coast of the Bay of Bengal, which includes the Sunderbans, has risen at an even faster rate at about 5 mm a year over the past two decades.