Natural Resources — Science STD 9 — Question

The removal and transportation of top soil from its original position to another place with the help of certain agents such as strong winds and fast running waters, is called soil erosion.
Causes of Soil Erosion:

1. Strong winds: The soil which is uncovered and loose, is eroded, when it is exposed to strong winds. The winds carry away the fine soil particles to other places.
2. Heavy rains: When rain falls on the unprotected top soil, rain water washes it down into the streams and rivers, etc.
3. Human actions: Human activities such as expansion of urban areas has led to removal of vegetation from certain regions. The bare land is thus exposed to agencies (winds, rains) of soil erosion.

Effects of Soil Erosion:

1. Loss of fertility and desertification: Soil erosion results in the displacement of the top soil from one region to another, thus, reducing its fertility. When the top fertile soil is constantly removed from a region, only infertile sub-soil is left behind. In such a soil, only sparse vegetation can grow. This way, soil erosion gradually turns lush green areas into deserts.
2. Landslides in hilly areas: Barren hills or hills with sparse vegetation are constantly exposed to heavy rain fall that makes the top soils of hills loose. Due to soil erosion, rock pieces of various sizes and loose soil from hills, suddenly slide down the steep slopes of mountains/hills. This phenomenon is called landslides. When these rock pieces and soil block the narrow river bed they result in floods. Sometimes, landslides block the roads and disrupt hill-life.
3. Flash floods: Vegetation in the hilly regions absorb a lot of rain water and keep the top soil intact. Barren hills or hills with sparse vegetation cannot absorb much rain water and thus can not keep the soil intact. So, heavy rains result in rapid movement of water in the areas resulting in flash floods in lower areas causing enormous loss to life and property.

Prevention of soil erosion:

1. Intensive cropping: If the fields remain covered with crops throughout the year, their top soil will not be exposed to winds or rains. In such a condition, no soil erosion will occur.
2. Sowing grasses and planting xerophytes: Soil should not be left uncovered. Sowing grasses on barren soil or planting of xerophytes will bind the loose soil. The roots of grasses and xerophytes hold the soil in place. Vegetative cover on the ground also helps in percolating water into deeper layers of soil.
3. Terrace farming (terracing): In terracing the slopes are divided into a number of flat fields to slow down the flow of water. In hilly regions, small crop fields are thus formed in the form of steps on terraces for cultivation of crops. Such terrace farms reduced the flow of rain water down the slopes of hills. Moreover, eroded soil from upper regions of hills gets deposited in lower terraces.