A recent report from the National Centre for Coastal Research (Ministry of Earth Sciences) titled ‘National Assessment of Shoreline Changes along the Indian coast’ has made a startling revelation. It states that almost one-third of the Indian coastline has been lost to soil erosion over the last 26 years. Out of the total coastline of 7,517 kilometres in India, a survey was conducted across 6,031 kilometres (excluding creeks), and 33% of this area was found to have suffered from erosion.
Regional Differences in Soil Erosion
The survey found that the eastern coast, adjacent to the Bay of Bengal, was more affected by erosion than the western coast, which shares its bounds with the relatively calm Arabian Sea. According to the report, West Bengal (63%) and Puducherry (57%) are the states most vulnerable to erosion. They are followed by Kerala and Tamil Nadu at 45% and 41%, respectively. Interestingly, Odisha on the eastern coast was the only state to report a coastline expansion of above 50%.
Gains via Land Accretion
Despite the worrisome levels of erosion, there have been areas where land accretion – or an increase in land area – was observed. The study reports that 29 percent of the surveyed coastline saw a gain in land due to soil or land accretion.
Data Sources for the Survey
The survey utilised data collected from five satellites – Landsat 5 and 7 (operated by NASA), ISRO’s Resourcesat 1 and 2, and Cartosat-1.
Factors Contributing to Soil Erosion
The study pinpoints several human-induced and natural factors leading to soil erosion. Faulty farming systems, deforestation caused by overgrazing, clearance of land for agriculture and construction, dam construction, diversion of river courses, and mining activities were listed as major contributors. In addition, environmental factors like rainfall intensity and runoff, the level of soil erodability, slope gradients, erosion history, and vegetation cover were identified as key elements affecting soil stability.
Coastline Characteristics of India
India’s coastline stretches for 7,517 km, including regions around the Andaman and Nicobar Islands in the Bay of Bengal and the Lakshadweep Islands in the Arabian Sea. Mainland India accounts for 6,100 km of this coastline and hosts several crucial ports such as Kandla, Mumbai, Navasheva, Mangalore, Cochin, Chennai, Tuticorin, Vishakapatnam, and Paradip.
Reasons behind the Eastern Coast’s Larger Erosion
The eastern coast witnessed more soil erosion than its western counterpart due to harsher conditions in the Bay of Bengal compared to the Arabian Sea. The constant rainfall and cyclonic activities from the Bay of Bengal, particularly during Southwest Monsoons (June to September) and Northeast Monsoons (October to December), led to the region being highly eroded.
Distinguishing Soil Erosion and Land Accretion
Erosion and accretion are two sides of the same coin. Soil erosion refers to the loss of land and human habitation at sea coastlines due to the washing away of soil regions. Conversely, soil accretion leads to an increase in land area. It is important to note that while accretion can result in enlarged land areas, it also has the potential to block inflows of seawater into deltas, estuaries, and creeks, which are vital habitats for numerous species of aquatic flora and fauna.