First national map of soil erodibility

Researchers at the Indian Institute of Technology (IIT), Delhi have developed a national-scale mapping of soil erodibility, a first of its kind in the country, according to an IIT Delhi press release.

The process of soil erosion starts when rainfall occurs on the soil or when water flow (runoff) displaces the soil particles. Soil erodibility is the susceptibility of soil particles from becoming detached and reflects the combined effect of rainfall, infiltration, and runoff. It is one of the major factors used to estimate soil loss and reflects the effect of soil structure, texture, permeability, and organic matter content in countering soil erosion. Till now, soil erodibility assessments have been conducted in specific regions or catchments, but a national-scale assessment of soil erodibility was required. A national-scale assessment of soil erodibility will be helpful in planning and implementing watershed management activities to deal with the soil erosion problem, which is currently missing over India. This National Map fills that gap.

This national-scale mapping of soil erodibility highlights specific areas where the soil is most prone towards erosion. The researchers in their study have found that out of the 50 districts with the most erodible soil, 29 are in Uttar Pradesh, 13 are in Bihar, 3 in Gujarat, 2 each in Haryana and Rajasthan, and 1 in Punjab. This study develops a comprehensive understanding of soil erodibility and its indices over India and will be an important dataset to perform soil loss estimations at a national scale.

“This reflects the combine contribution to erosion due to rainfall, runoff, land use, land cover, deforestation, and agricultural practices. This study fills a critical gap and brings us one step closer to estimating soil loss at a national level and developing a soil erosion model”, said Prof. Manabendra Saharia, Department of Civil Engineering, IIT Delhi, in the press release,

Prof. Saharia added, “Soil erosion is a significant trigger for land degradation and a major global geo-environmental issue. Being able to assess its causes and impacts at a high-resolution will help us develop a national soil conservation plan that can help our vital agricultural sector”.

As the Introduction to the study points out, soil erosion is a major trigger for land degradation and has been identified as one of the leading environmental problems, the globe is facing. Soil erosion contributes around 15–30 billion tons of sediment, which is transported annually by the major rivers of the world into oceans, accounting for approximately 46% of the total land degradation. In India, approximately 45% of the total geographical area of the nation is susceptible to soil erosion.

The IIT Delhi researchers said that till now, soil erodibility assessments have been conducted in specific regions or catchments, but a national-scale assessment of soil erodibility was required. The researchers also conducted a comprehensive statistical analysis of the soil erodibility map to visualize its distribution over the national territory in terms of the different soil types, textures, and percentage ranges of erodibility values.

The study exploring the spatial variation of soil erodibility and its relationships with soil properties in India was published in the journal CATENA. The IIT Delhi press release said that the dataset has been freely released as the Indian Soil Erodibility Dataset at a spatial resolution of 250 m. The study estimated national average soil erodibility factors for India using Nomograph and EPIC models, respectively.

This study is an attempt to map soil erodibility and its distribution throughout the nation and check the applicability of erodibility indices to estimate soil erodibility factors in the Indian region. High-resolution (250 m) input datasets for soil erodibility estimation were downloaded and processed to get erodibility indices over India.

An earlier IIT Delhi study had pointed out that a large proportion of the total eroded soil in India is due to erosion by water, and rainfall erosivity is one of the major components. Rainfall erosivity is a measure of the erosive force of rainfall which represents the potential of rain to cause soil erosion. This study was also the first such national-scale assessment of rainfall erosivity over India using gridded precipitation datasets, which will aid in understanding and mitigating rainfall-induced erosion. The earlier available assessments of rainfall erosivity in India are largely based on rain-gauge recordings and surveys, which hinders its estimation and understanding over large areas. The study utilized multiple national and global gridded precipitation datasets to develop a high-resolution rainfall erosivity factor map to highlight areas prone to rainfall-induced erosion.