Environmental Science

ENVIRONMENTAL SCIENCE : NATURAL RESOURCES 93

Estimates of Excessive Erosion of

Top Soil from World Cropland

Grand Total

Rest of World

To ta l

USA

India

China

0 10,0

00

20,0

00

30,0

00

40,0

00

Total Cropland

M illion A cres

Excessive Loss

Million Tones

Fig. 2.6

Agents of Soil Erosion

The various agents that bring about soil erosion are as under:-

Water Erosion

Water removes the soil by falling on as rain drops, a well as by its surface flow action,
It may be of three types:

(i) Sheet erosion

Here the removed soil is like a thin covering from large area. This sheet is more or less
uniform.

(ii) Rill erosion

If sheet erosion occurs with full force, the run off water moves rapidly over the soil
surface. It cuts well-defined finger-shaped groove like structures, It appears as thin channels
or streams. These are known as rill erosions.

(iii) Gully erosion

This results due to the convergence of several rills or thin channels formed during rill
erosion towards the steep slope. When they join together, they form wider channels of water,
known as gullies. In case of further rains these gullies may become still wider and deeper.