Environmental Science

Slipping away from the surface

Study finds an increase in the rate of soil erosion post the extreme floods in August 2018

April 16, 2021
The Scitech

In a study, published in the Journal of the Indian Society of Remote Sensing, researchers from the Indian Institute of Technology Bombay (IIT Bombay) and Rural Data Research and Analysis (RuDRA), Mumbai, assessed the soil erosion rates before, during and after the Kerala 2018 floods. This data helped in understanding the extent of damage caused by the floods to the land and soil system in the state and can guide the relief measures needed to improve the overall conservation of natural resources. The researchers studied the factors affecting soil erosion rates using data such as precipitation and rainfall, digital soil map, elevations in the land and satellite imagery obtained from remote sensing platforms. They also analysed the variation in soil erosion rates across the state. The results were startling.  

“Rainfall in Kerala has always been higher than the average values due to the orographic effect from the Western Ghats, which is due to the undulating topography,” said Prof Pennan Chinnasamy from the Center for Technology Alternatives for Rural Areas (CTARA), IIT Bombay.  “With such higher rainfall rates in Kerala, it is necessary to protect the land from excess soil erosion as the rainfall quantitatively represents the impact on the soil surface,” he added. The Soil Erodibility Factor, estimating the susceptibility of the soil to erosion, was on the higher end, with the highest in Alappuzha district, indicating that the sandy soil present across the state is prone to erosion. This factor also pointed towards the highly undulating topography of the Western Ghats. The Cover Management Factor analysis showed that the vegetation cover decreased by around 63% from January 2018 to August 2018. The vegetative land was converted to near barren condition due to the floods, making it further susceptible to soil erosion.  Similarly, the average Conservation Practice Factor, which quantifies the lack of impact of the soil and water conservation measures on minimising soil erosion, increased from 0.8 in January 2018 to 0.89 in August 2018. The highest increase, from 0.5 to 1, was seen in Idukki, Kottayam, Ernakulam and Thrissur. The increase points towards cropland damage due to waterlogging and washing away of topsoil due to the floods.  

On similar lines, the rate and total amount of sediment deposited increased dramatically during the 2018 floods, with Idukki being the worst affected. The data also shows that the high erosion rates are not only due to the heavy rainfall but also because of the unsustainable conversion of natural land into human settlements. It is, therefore, necessary to understand and improve the methods of human settlement and soil management towards a more sustainable, climate-friendly future.

Source: IIT Bombay news release