9 of 20 India’s districts susceptible to soil erosion are in Assam

Guwahati, March 25: In a development that comes with disturbing implications for the State, nine out of the country's 20 districts with the highest susceptibility to soil erosion are in Assam. The districts are Goalpara, Dhubri, Chirang, Baksa, Kokrajhar, Bongaigaon, Udalguri, Nalbari, and Barpeta.

This is the first time that a novel impact-based erosion-severity classification system has been introduced in the country covering 28 states and eight Union territories, which found that 29.46 per cent of the country's landmass is prone to minor erosion, while 3.17 per cent experiences catastrophic erosion.

Significantly, Assam leaves the other states vis-a-vis vulnerability to erosion by a long stretch, with Meghalaya, Himachal Pradesh, and Jammu & Kashmir accounting for just three districts each, placing the three in the combined second place.

"This is the first comprehensive national-scale assessment of both soil erosion and sediment yield mapping over India which has thrown new light on a wide gamut of inter-related issues. The consequent classification system will enable the planning and implementation of soil conservation strategies locally as well as nationally," Dr Narendra Kumar Lenka, principal scientist at the Indian Institute of Soil Science ICAR, told The Assam Tribune.

The study also reveals that the Brahmaputra basin has the maximum risk of soil erosion at 47.64 tonnes/hectare/year (t/ha/yr), followed by the Mahanadi basin at 28.42 t/ha/yr, and the Ganga basin at 25.07 t/ha/yr. The non-Indus basin was observed to experience the least soil losses at 3.22 t/ha/yr.

According to the study, approximately five per cent of the nation's geographical area, covering significant portions of Assam - and some portions of Meghalaya, and Himachal Pradesh - has been classified under the E6 (catastrophic) erosion category, with mean PSL values greater than 100 t/ha/yr. This (E6) class has potential to damage roads, fences and even buildings by creating deep gullies.

The findings of the study titled 'Geospatial modelling and mapping of soil erosion in India' by Ravi Raj and Manabendra Saharia of the department of civil engineering, IIT Delhi, and Sumedha Chakma of Yardi School of Artificial Intelligence, IIT Delhi, were published in Catena by Elsevier.

"Five out of 23 basins have annual potential soil losses greater than the national average soil loss. The main reason for higher PSL values in the Brahmaputra and Ganga basins is due to the new soil layer formation every year due to flooded water. This new soil layer has very less capacity to withstand erosive forces raised due to rainfall and runoff," the study noted.

More than 78 million hectares of agricultural land in India experience an average productivity loss of eight per cent. Rainfall erosivity (R-factor) emerges as the most crucial feature in estimating soil erosion in Indian conditions. Additionally, when the combined impact was assessed, rainfall intensity, combined with the topographic factor, demonstrated the highest influence on soil erosion.

- By Sivasish Thakur