Question

The characteristics of the raindrops, which are important from soil erosion point of view are:
A. Raindrop size
B. Terminal velocity
C. Kinetic energy
D. Drop size distribution
Choose the correct answer from the options given below:

• A. A, C and D only
• B. A, B and D only
• C. A, B and C only
• D. A, B, C and D

Hint:

Soil erosion by rainfall is all about the kinetic energy (\(KE = \frac{1}{2}mv^2\)) of the raindrops. All the other factors listed (size, velocity, distribution) are components that determine the total kinetic energy delivered by a storm.

Answer 1

The Correct Option is D

Step 1: Understand the mechanism of splash erosion. Splash erosion is the first stage of water erosion, caused by the impact of raindrops on the soil surface. The energy of the falling raindrop detaches soil particles, making them available for transport by runoff.
Step 2: Evaluate the importance of each characteristic.
- A. Raindrop size: The size of a raindrop determines its mass (\(m\)). Larger drops have more mass and thus more potential to cause erosion.
- B. Terminal velocity: This is the constant speed that a freely falling drop eventually reaches when the resistance of the air equals the force of gravity. A higher terminal velocity (\(v\)) means a harder impact.
- C. Kinetic energy: The energy of the raindrop at impact is given by \(KE = \frac{1}{2}mv^2\). This is the direct measure of the raindrop's capacity to do work, i.e., to detach soil particles. It is a function of both size (mass) and terminal velocity
. - D. Drop size distribution: A rainfall event consists of drops of various sizes. The overall erosivity of a storm depends on the distribution of these sizes. A storm with a higher proportion of large drops will be more erosive than one with the same total rainfall but composed of smaller drops.
Step 3: Conclude the correct combination. All four characteristics—size, terminal velocity, the resulting kinetic energy, and the distribution of drop sizes—are fundamentally important in determining the erosive power of rainfall.