New Delhi: According to a study by the Indian Space Research Organization (ISRO), India has lost more than 3,680 hectares of land to coastal erosion in 10 years, with West Bengal and Gujarat the worst hit.
The study conducted by ISRO’s Space Applications Centre, Ahmedabad on comprehensive data available between 2004-06 and 2014-16 shows that 15 per cent of India’s coastline – which is about 1,144 km – is eroding. Meanwhile, 14 percent of India’s coastline – ie 1,084 km – is growing
The world’s coastlines are constantly changing due to natural processes such as coastal erosion and accretion, as well as human activities that affect sediment transport.
However, projected sea level rise, increased wave activity and projected increases in the frequency and intensity of tropical cyclones due to climate change are expected to lead to more rapid and severe coastal changes in the near future, the researchers said in the report, to be published soon in the peer-reviewed journal Current Science.
Coastal erosion means acres of land are disappearing. This can lead to habitat loss for native animals and plants and make people living in coastal areas vulnerable – their land disappears and they are closer to the sea.
Accretion is the process by which coastal sediments return to visible portions of a beach or shore after submergence. A sustainable beach or foreshore often goes through a cycle of subsidence during rough weather and growth during calm periods.
Growth can be profitable in some cases due to increase in land area. But it can also harm marine life – such as marine animals suddenly finding their waters shallower or turtle habitats moving away from shore.
According to the research team’s estimates, India gained 4,042 hectares of coastal area between 2004-06 and 2014-16. Although there is a net gain in total coastal area (due to silt/sand deposition), the eroded stretch is greater than the coastal shoreline.
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changing shore
According to a 2020 European StudyThe world is set to lose half of its sandy beaches by the end of the century due to coastal erosion caused by rising sea levels.
Coastal environments naturally tend to balance sediment supply along the coast — taking up sediment and then bringing it back to shore in a cycle — but high wave activity during monsoons, cyclones, and human activities such as coastal construction and dam construction can disrupt this. Equilibrium, leading to changes in shorelines.
Keeping track of changes in coastal zones helps in planning for sustainable development activities in coastal zones.
HTA mapping with ISRO satellite images
Researchers consider the high tide line (HTL) as the coastline. Using images from the LISS-IV sensors on ISRO’s Resourcesat-1 and 2 satellites, the team was able to map the HTL of the Indian coastal states with a spatial resolution of 5.8 m corresponding to the 2004-06 and 2014-16 time frames.
For different states, HTL is represented by different landscape indicators — such as mangroves, cliffs, seawalls, or permanent vegetation lines. The team used a digitization technique to map the coastlines for each state.
The team found that the Andaman and Nicobar Islands have the longest eroded coastline (231 km) and the longest extended coastline (256 km). Erosion is lowest in the Lakshadweep Islands (12 km), and the shortest length of extended coastline is in Goa (7 km).
West Bengal (36 percent), Odisha (32 percent), Kerala (23 percent) and Andhra Pradesh (23 percent) have the highest percentage of eroding coastlines. The remaining maritime states have less than 20 percent eroded coastline, with Lakshadweep recording the lowest (8 percent).
Andhra has the highest percentage of coastline (26 per cent), followed by Tamil Nadu, Odisha and West Bengal (22 per cent each) and Kerala (21 per cent).
The percentage of stable coastline is highest for Gujarat (87 percent), followed by Lakshadweep (82 percent). The figure is 80 percent for Maharashtra and Goa.
On the east coast the coastline varies higher
Coastal change is greater on the east coast of the Indian peninsula than on the west coast.
West Bengal, Gujarat, Odisha and Goa experienced a net loss of coastal areas due to erosion within 10 years. The loss is highest for West Bengal (252 ha).
Meanwhile Tamil Nadu, Maharashtra, Karnataka, Kerala, Andhra Pradesh and Lakshadweep have gained coastal land. Andaman and Nicobar Islands (524 ha) had the highest gain.
“Since coastal erosion poses a serious threat to both the ecology and economy of the country, Coastline change data is primary data for coastal planning development activities,” the researchers said in the report.
“The Coastal Change Atlas depicts changes in shorelines. However, planning for coastal development activities should also include an assessment of expected coastal changes under climate change scenarios,” they write.
(Edited by Geetalakshmi Ramanathan)
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