Question

Give three chief characteristics of Alluvial soil.

Answer 1

Hint:They are also called the ‘kidneys of the earth’. They are present along the river banks, deltas and in floodplains.

Complete answer:
Alluvial soil is also called Alluvium. It is loose and unconsolidated soil. It is the soil or sediment that has been eroded from places that are upstream, reshaped by the forces of water and redeposited by the water body at some other place (generally a non-marine setting). Hence, they are found along the rivers, in floodplains and at river deltas. For e.g. the Indo-Gangetic plains are the floodplains and the northern plains of India along the banks of river Ganga and its tributaries. The Mississippi delta and the Sundarbans delta are also sites where alluvium can be found.
It is generally composed of various materials such as fine particles of clay and silt. It also includes larger particles of gravel and sand. This rock transformation process that leads to the formation of alluvium takes over thousands of years to occur.
Other than being fertile, these soils also act as a very good filter for the water flowing adjacent to these soil. They remove contaminants from the river water and improve its quality for downstream communities.
Like any other feature of the earth, this too is prone to damage by human activities. For e.g. deforestations and construction activities cause erosion. When a land is deforested and the soil gets eroded, the soil loses it fertility, but the eroded soil will eventually be deposited to some other place where it would be beneficial. But when the eroded soil is contaminated with waste products from construction sites or just random urban pollutants, then the flood deposition in the new place will be met with the same contamination.

Note:In India, there are two types of alluvial soil that are found. Based on their age, they are Bhangar (Old Alluvium) and Khadar (New Alluvium). Bhangar soil is less fertile as it contains more nodules (kankar) whereas Khadar soil is more fertile as it contains more amount of silt and clay.