Answer Writing Practice for UPSC IAS Mains Exam: Paper - II (General Studies – I) - 05 September 2018

Answer Writing Practice for UPSC IAS Mains Exam

UPSC Syllabus:

  • Paper-II: General Studies - I (Indian Heritage and Culture, History and Geography of the World and Society)

Q. What do you understand by soil profile? Discuss the impact that floods have on the soil. (250 words)

Model Answer:


  • Why in news?
  • Soil and Soil profile
  • Positive impact
  • Negative impact
  • Conclusion

Why in news?

As the rains abate in Kerala and parts of Kodagu district in Karnataka, the loss of lives and the devastation of infrastructure and crops is apparent. However, as rebuilding is planned, what is often ignored is the soil that has been washed away. 

Soil and Soil profile

Soil is the topmost layer of the earth's surface. It consists of a mixture of minute particles of disintegrated rocks, minerals, organic matter and bacteria. Soil is formed when forces of nature such as temperature, rain, wind, waves, animals and plants act on rocks and break them into tiny pieces over a long period of time. The process of soil formation is known as Pedogenesis.

The different layers of the soil are arranged in a vertical manner, which is known as the soil profile. The layers are usually horizontal in orientation, parallel to the soil surface.

Each layer of the soil is termed a horizon. Each layer differs the ones adjacent to it in terms of colour, texture, chemical composition, and depth.

Positive impact

Not all floods are bad for the soil, as seen in the often-occurring floods along the banks of the Ganga, Kosi, Brahmaputra and other rivers taking birth in the Himalayas. There, the gushing river emanating from the mountains carries with it loosened alluvial soil, and not only washes over farmlands, but also replenishes flood plains with fertile soil.

Negative impact

  • However, in south and central India, floods wash away rich, weathered soil, which are deposited in reservoirs or as sand bars along the river bed or in the sea. Soil takes thousands of years to form through natural processes.
  • Soil degradation due to flooding is a serious concern. A 2014 review of soil degradation in India by multiple institutions shows that an estimated 14 million hectares suffer soil degradation due to flooding annually.
  • The impact of floods on soil was also studied in detail following the 2009 floods in North Karnataka. Researchers from the National Bureau of Soil Survey and Land Use Planning (NBSS&LUP) and other institutes estimate that 13 flood-hit districts lost 287 million tonnes of top soil and soil nutrients across 10.75 million hectares of farmland. Under market prices, the replacement of nutrients such as nitrates, phosphates and iron would have cost 1,625 crore, while another Rs. 853 crore would have been spent on replenishing organic material lost.
  • A soil profile of a few affected districts, done under the State’s integrated watershed scheme, shows large swathes of these areas having “shallow or very shallow” soil depth, organic carbon deficiency, and low productivity of land. To recover and replace would take a “considerable” amount of time, and a steadfast programme of recovery.
  • The gradual loss of soil productivity due to flooding can have a lasting impact on the local economy.


The loss of soil productivity due to flooding can lead to low productivity impacting the local economy and living standard of cultivators therefore any rehabilitation programme must consider this lost soil.

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